WO2005053883A2 - Infiltrating a powder metal skeleton by a similar alloy with depressed melting point exploiting a persistent liquid phase at equilibrium, suitable for fabricating steel parts - Google Patents
Infiltrating a powder metal skeleton by a similar alloy with depressed melting point exploiting a persistent liquid phase at equilibrium, suitable for fabricating steel parts Download PDFInfo
- Publication number
- WO2005053883A2 WO2005053883A2 PCT/US2004/039133 US2004039133W WO2005053883A2 WO 2005053883 A2 WO2005053883 A2 WO 2005053883A2 US 2004039133 W US2004039133 W US 2004039133W WO 2005053883 A2 WO2005053883 A2 WO 2005053883A2
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- skeleton
- infiltrant
- composition
- mpd
- mass percentage
- Prior art date
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C33/00—Making ferrous alloys
- C22C33/02—Making ferrous alloys by powder metallurgy
- C22C33/0242—Making ferrous alloys by powder metallurgy using the impregnating technique
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B33—ADDITIVE MANUFACTURING TECHNOLOGY
- B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
- B33Y80/00—Products made by additive manufacturing
Definitions
- Figs. 1A, IB and 1C are a schematic representation of a skeleton of particles being infiltrated, showing three stages of infiltration: Fig. 1A - initial, Fig. IB - half way and Fig. 1C - complete;
- Fig. 2 is a Phase Diagram showing a system of Fe- 12%Cr showing temperature °C v. wt% carbon;
- Fig. 3 is a Phase Diagram for D2 steel showing temperature °C v. wt% carbon
- Fig. 4 is an isothermal phase diagram for D2 steel showing equilibrium compositions at 1306 °C, 60% vol solid, showing wt% Cr vs. wt% C, for skeleton and infiltrant complementary pairs for basic, near tie-line, off tie-line, and reverse slope modes;
- Fig. 6 is a schematic phase diagram relating temperature °C to wt% C, showing a case that can achieve complete solubility of the MPD (C) in an iron skeleton, which can be fully homogenized.
- Fig. 7 is a schematic phase diagram relating temperature °C to wt% C, showing a case that can achieve partial solubility of the MPD (C) in an iron skeleton, which can be partially homogenized.
- Fig. 8 is a schematic phase diagram relating temperature "C to wt% B, showing a case that can achieve virtually no solubility of the MPD (B) in an iron skeleton, which can be only slightly homogenized.
- Fig. 9 is a schematic flowchart in two parts, A and B, showing steps to design an infiltration system that is generally packing fraction driven, and to infiltrate a l skeleton;
- Fig. 10 is a schematic flow chart in two parts, A and B, showing steps to design an infiltration system that is generally skeleton composition driven, and to infiltrate such a skeleton;
- Fig. 11 is an isothermal phase diagram at 1279 °C for D2 steels showing equilibrium compositions, 70% solid;
- Fig. 12 is an isothermal phase diagram at 1279 °C for D2 steel, showing equilibrium compositions of 70% vol solid, for infiltrating a skeleton of 60% vol solid;
- Fig. 13 is an isothermal diagram for A3 steel, showing equilibrium compositions at 1351 °C for 60% vol skeleton, showing wt% Cr vs. wt% C, for skeleton and infiltrant pairs for basic, near tie-line and off tie-line modes, with concentrations of Mo and V being functions of concentration of Cr;
- Fig. 14 is a phase diagram for A3 steel, showing equilibrium compositions at 1351 °C for 60% vol solid and 1330 °C for 70% vol solid;
- Fig. 15 is an isothermal phase diagram for Cn-7MS steel at 1261 °C, relating wt% Cr to wt% Si, for a 60% vol solid;
- Fig. 16 is a phase diagram for Cn-7MS steel, relating temperature "C to wt% Si;
- Fig. 18 is an isothermal phase diagram for Austenitic-Manganese steel grade C at 1295 °C, relating wt% Mn to wt% C;
- Fig. 19 is a phase diagram for Austenitic Manganese steel grade C relating temperature °C to wt% C;
- Fig. 20 is a schematic diagram relating temperature °C to wt% C, showing lines of different vol% solid at equilibrium for Fe with 12% Cr;
- C is used as the major melting point depressant (MPD) element
- silicon (Si) is used as a second MPD element
- Cr chromium
- Mc-. ⁇ is mass (or weight) % Cr.
- T is target composition.
- M MPD - max , ⁇ is the maximum concentration of MPD in this target composition, T.
- M Cr _ s is mass % Cr.
- V s is total volume % solid at the infiltration temperature (60% is typical in most discussions herein) .
- V s 100 - V L .
- M s is total mass% solid .
- a number in the subscript refers to a Mass % solid measured at the volume % specified by the subscript.
- V L is total volume % liquid (40% is typical in most discussions herein) .
- V L 100 - V s .
- M L is total mass% liquid.
- M c _ eu - The amount of carbon present at the eutectic composition.
- M cr# ⁇ is mass % Cr.
- M ⁇ is mass % solid of skeleton based on the packing fraction of the powder and instantaneous infiltration of Infiltrant.
- M ⁇ M s .
- a number (or PF) in the subscript refers to the mass % solid measured at the volume fraction specified by the subscript (or the packing fraction of the skeleton.)
- V ⁇ is the volume % of the skeleton, also known as the packing fraction.
- V PF V ⁇ .
- KB The skeleton composition in a near tie-line style.
- KC The skeleton composition in an off tie-line style.
- M Cr#I is mass % Cr.
- Mj is mass % infiltrant, based on void fraction of skeleton, assuming instantaneous infiltration of infiltrant.
- Vj is the volume fraction of the infiltrant, also known as the void fraction of the skeleton.
- V VF V ⁇ .
- T IL The liquidus temperature of the infiltrant.
- ⁇ _ nf ii The infiltration temperature.
- IA The infiltrant composition in a basic style.
- Si,K Psi - ⁇ Si.S' Typically, 0 ⁇ P SI ⁇ l/3 or 0 ⁇ P c ⁇ l /3 .
- the near tie line style method is used.
- the reverse slope style method is used.
- a different parameter R may be used for each non-MPD element .
- infiltration can be done extremely rapidly by the application of external pressure.
- this requires a mold and typically expensive processing equipment .
- the inventions disclosed herein are directed to pressureless infiltration, where the primary driving force for infiltration is capillarity.
- a vacuum pressure is created around both the porous skeleton and the infiltrant source. This vacuum is to remove any gases that might be residing within the skeleton, which could prevent infiltrant from filling the skeleton at the location of the gas.
- Pressureless or “capillary” infiltration as used herein means such infiltration, without the application of a pressure difference between the infiltrant source and the pore spaces within the skeleton, whether or not a vacuum is applied around both.
- FIGs. 1A-1C show such pressureless infiltration at three representative stages.
- an infiltrant pool 120 is below a porous skeleton 122, which is composed of interconnected, adhered particles.
- Fig. 1A shows infiltration at the moment shown in Fig. 1A.
- infiltration has not yet begun.
- the skeleton 122 has been brought into contact with the infiltrant in a pool 120, and infiltrant 124 has been drawn up into the skeleton 122 by capillary forces, about half-way to its top.
- the infiltrant 124 has been drawn all the way to the top of the skeleton 122, fully infiltrating it.
- a general concept, explored more fully below, is to use an infiltrant composition similar to that of the powder skeleton, but with the addition of a material such that the melting point of the infiltrant is depressed relative to that of the skeleton.
- the infiltrant quickly fills the powder skeleton.
- the infiltrant and skeleton system it is important to design the infiltrant and skeleton system so that the infiltrant has the chance to fill the entire open pore space of the skeleton before solidification and freeze off takes place.
- TLI transient liquid phase infiltration
- the WO 02/094484A1 publication discusses systems where infiltration completes, followed by diffusional solidification at the infiltration temperature, resulting in a fully solid part at equilibrium. It also discusses some cases where, even after the part has reached its equilibrium condition at the infiltration temperature, some of the infiltrant in the skeleton will remain liquid after diffusional solidification has ceased. Those cases are referred to generally therein as low solubility cases, because the agents that depress the melting point of the infiltrant, relative to the similar composition of the skeleton, have a relatively low solubility in the skeleton. In some such circumstances, the final microstructure that results is not homogeneous, but rather is similar to that typically obtained with a cast part, which also may be a useful result.
- an Aluminum (Al) skeleton can be infused with an infiltrant of an Al and silicon (Si) alloy, which has a lower melting point than pure Al .
- Pure aluminum has a melting point temperature of ⁇ 660 a C.
- Silicon is used extensively in die casting alloys to improve fluidity of the melt.
- An Al alloy with 12% Si has a melting point of 577 °C, resulting in depression of its melting point by about 83 °C from that of pure Al .
- An aluminum alloy commonly used in die casting of automotive pistons (336.0) contains 12% Si, 2.5% Ni, %1 Mg, and 1% Cu, and has an even lower melting range with a solidus of 540°C and a liquidus of 565°C.
- the diffusivity of silicon in aluminum is ⁇ 10 "12 m 2 /s at 600°C.
- the maximum solubility of silicon in aluminum is about 1.6% wt, which is relatively low (as compared, for instance, to that of Carbon (C) in iron (Fe) ) .
- the low solubility of Si, as an MPD can lead to some infiltrant remaining liquid, such that the liquid flow in the aluminum skeleton never chokes off from solidification. This is because, if the final (target) bulk composition has an MPD (eg. Si) concentration that is greater than the concentration of the MPD in the solidus (equilibrium solid) composition, the part will only undergo partial diffusional solidification at the infiltration temperature.
- MPD eg. Si
- Solidification is only partial, because it takes relatively little silicon to saturate the aluminum into which it might otherwise diffuse. Thus, there is no excess solubility in the aluminum for more than a small amount of silicon to diffuse into the aluminum skeleton. Therefore, there may result an end product that has higher concentrations of silicon in the regions that had been liquid than the regions that had been solid w Ihich may, in some circumstances, be undesireable. Furthermore, it will be impossible to infiltrate a reasonably dense skeleton (e.g. > 50% packing fraction) and to achieve a body having a bulk composition with Si concentration > 7% for reasons explained below in a discussion regarding solubility. But, most commonly used aluminum and silicon alloys have between about 7 and 15% Si concentration in the bulk composition.
- ASTM International standards set forth the chemical specifications of the alloy types listed: A681 Tool steel alloy - family types H, D A, 0 and S; A600 High speed tool steel - family types M and T; A781/A784 steel and alloy casting alloys - including types CN-7MS and CF-lOSMnN and HF; A276 Austenitic and Martensitic stainless steels including type 410 and 440C; A128 Austenitic Manganese alloys.
- ASTM International standard A597 contains cast versions of the following tool steels: A2 , D2, D5, S5, M2 , S7 , H12, H13 and 01. The cast chemistries are similar to the wrought ones, with allowances made for minor impurity elements .
- the D family are high carbon, high chromium, cold work tool steels.
- the M family are molybdenum, high speed steels.
- the T family are tungsten, high speed steels.
- the H family are chromium hot work, heat resistant steels.
- the A family are air hardening, medium alloy, cold work steels.
- the 0 family are oil hardening, cold work steels.
- the S family are shock resisting steels.
- the 4XX family are martensitic/ferritic stainless steels.
- the C-type castings are corrosion resistant steels.
- H-type steel castings are heat resistant stainless steels.
- a general invention disclosed herein is a fully densified substantially homogeneous steel part made by infiltrating a skeleton made from steel powder with an infiltrant of a similar composition.
- the compositions of the powder and the infiltrant differ primarily only in that the infiltrant has a higher concentration of a melting point depressant agent "MPD" than does the skeleton, and this higher concentration results in the infiltrant having a melting point that is significantly lower than that of the skeleton composition.
- the melting point depressant agent acts as a melting point depressant.
- Carbon (C) can act as a melting point depressant agent for steel compositions .
- both the skeleton and the infiltrant contain some of the melting point depressant agent, e.g., C, but just that the concentration of the melting point depressant agent in the infiltrant is greater than it is in the skeleton.
- the melting point depressant agent need not be totally absent from the skeleton.
- the present inventors have discovered, an unexpected combination of conditions that can provide a relatively homogeneous, fully metal, fully dense steel part.
- certain formulations of steel can be used as a target composition.
- At least one of the elements that makes up the normal, target formulation, typically carbon or silicon is an element that can act as a melting point depressant for the composition of the remaining elements, or, in some cases, a composition of most, but not all of the remaining elements.
- a skeleton is made that has all of the elemental components of the target steel formulation, in concentration that are near to those of the target, but with two differences. First, there is a lower concentration of the melting point depressant.
- the presence of some or all of the other elements are in slightly different concentration, because there is less MPD.
- concentration of Fe is higher in the skeleton than it is in the infiltrant.
- concentrations of other elements such as carbide formers, such as chromium (Cr) , also differ between the skeleton and target.
- An infiltrant is provided that has all of the elemental components of the target steel formulation, in concentrations that are near to those of the target, but with two similar differences. First, there is a higher concentration of the melting point depressant. Second, the presence of at least one of the other elements are in slightly different concentrations because there is more MPD. For instance, the concentration of Fe is lower in the infiltrant than it is in the skeleton. Similar to skeleton formulations, elements other than iron can also vary in concentration between target and infiltrant.
- compositions of the infiltrant, and the skeleton can be chosen such that a skeleton will remain solid at a temperature at which the infiltrant can be melted and fully infiltrated into the skeleton primarily by capillarity.
- the liquid phase has a higher concentration of the melting point depressant than does the skeleton. Some, but not all of the melting point depressant will diffuse from the liquid phase to the solid phase. Freeze off does not occur because the liquid phase persists, keeping the flow channels open.
- the system is designed so that the persistent liquid phase is large enough (greater than at least 7% vol, and more typically between 20 and 40 vol % of the infiltrated body) so that flow can be maintained.
- the solid and the liquid phases remaining after any diffusional solidification have different compositions. But, typically the degree of difference is slight, and the full part is substantially homogeneous.
- Conventional heat treating techniques such as austenitizing, quenching, or slow cooling and tempering can be applied to infiltrated bodies to affect homogeneity and mechanical properties as explained below.
- Important disclosures herein are methods of infiltrating a steel skeleton with an infiltrant of similar composition, but where a melting point depressant is provided.
- the melting point depressant can be carbon alone, despite the high diffusivity of carbon in iron. It can also be silicon alone, again despite the relatively high diffusivity of Si in iron. And, it can be carbon and silicon together. Additional elements are not required, for instance to achieve greater melting point depression without risking choking off of infiltration by freezing. In fact, certain additional melting point depressing elements may be detrimental, if their diffusivity is so low that they prevent a reasonable degree of homogenization during a reasonable time, or, if their solubility is so low that they prevent a reasonable degree of homogenization at all.
- inventions disclosed herein include: parts made according to such methods; the methods of making such parts; actual formulations themselves for use as skeletons, infiltrant, and skeleton and infiltrant pairs relative to a specified target; and methods of determining the compositions of such formulations .
- Figs. 1A-1C The foregoing is illustrated with the following very simplified example and Figs. 1A-1C.
- a commercial steel with the target formulation as set forth in Table A below in the row entitled target, namely 70% wt Fe, 2% wt C and 10% wt for each of Cr and Mn.
- the initial skeleton 122 is 50% volume solid, and 50% volume void pore space. (This is not likely a practical arrangement, but it is not too far from a typical, for three ' dimensional printing, solid volume of 60%, and greatly simplifies calculations for this initial example.)
- the carbon concentration in the target composition is 2% wt.
- the target, infiltrant and skeleton all have the same concentrations of the non-MPD elements, Cr and Mn, other than Fe.
- the difference in concentration due to the variation in MPD (C) amount is offset by corresponding differences in iron Fe concentration.
- the 50/50 solid/void volume packing fraction values for the skeleton would more typically be between about 20% and about 40% vol void, and correspondingly, between about 80% and about 60% vol solid.
- the target Mn and Cr are both 10% wt. In a multi-component system, such as the steels under discussion here, it is very typical for all of the non-Fe components to be present in significantly unequal concentrations.
- the concentration of each of the non-Fe components other than the carbon is the same in the target, the infiltrant, and in the skeleton. Such a method is identified herein as a basic method, and it is very useful.
- the elemental composition concentrations are weight percentages (indicated herein as x% wt)
- the packing fractions are volume percentages (indicated herein as y% vol) .
- Another important point is that one step in a method disclosed herein requires analyzing a two phase system, that is part liquid and part solid at equilibrium. Those parts are also quantified by volume percentages. Further, the mass fraction of a phase, for instance the solid, is not the same as the volume fraction of the same phase, because the density of a solid may differ from density of liquid of the same composition.
- Fig. 2 shows a phase diagram applicable to a simple martensitic stainless steel with 12% Cr, relating temperature to weight percent carbon.
- the point K is a composition of stainless steel with .57% wt C, which is a composition used as a skeleton.
- the point T is the target bulk composition of an infiltrated product, which is in a two-phase field (liquid + austenite) having 1.5% wt C.
- the point I is the composition of an infiltrant, which has 3.07% wt C.
- the points K, T and I are all with 12% wt Cr, and are at 1353°C (1626 K) . If a skeleton having 60% vol solid and 40% vol void of composition K (0.57% wt C) is infiltrated with an infiltrant having a composition I, the final bulk composition of the infiltrated target will be T.
- the equilibrium composition will be composed of 60% vol solid, having about .97% wt C, and 40% vol liquid, having about 2.37% wt C. These are the concentrations at the infiltration temperature of 1353 "C for the intersections of the solidus and liquidus respectively.
- the skeleton and infiltrant compositions, skeleton packing fraction and infiltration temperature were chosen so that the final bulk composition would be equilibrium at T, with a 60% vol. solid phase and a 40% vol. liquid phase. It is somewhat artificial that the solid phase of 60% vol. is the same as the packing fraction of 60%. There are some restrictions on the relationship of these two parameters, but, they need not be equal. What is required, is that the equilibrium liquid phase percent be large enough to ensure flow of infiltrant at equilibrium.
- the minimum theoretical volume is between about 7% vol and 20% vol, depending on whether a hipping model or a percolation model is used. The designer must choose the most appropriate value given the system. There must be interconnection in three orthogonal dimensions. A typical preferred range is between about 20% and about 40% vol., putting the solid phase at between about 60% and about 80%. What is further required, is that the volume % of the equilibrium solid phase should not be less than that of the skeleton packing fraction. If it were, then some part of the skeleton would need to have been dissolved during equilibration. That is not desireable.
- This equilibrium condition can be shown using standard techniques, and analytical tools, such as phase diagrams, the lever rule, etc, as set forth generally in Physical Metallurgy, Robert W. Cahn, Peter Haasen, New York, NY (1996) .
- a software program can be used, such as Thermo- Calc software, available from Thermo-Calc Software, of Sweden; or Pandat, available from Computherm, of Madison, WI; or MTDATA, available from National Physical Laboratory, of the U.K.; or Factsage, available from autoimmune Polytechnique de Montreal, Canada.
- the following table shows the compositions of the target, skeleton (K 60%) and infiltrant (I 40%) in a similar manner as the example above is shown. It also shows the equilibrium liquid and solid compositions.
- the packing fraction is 60% solid, and, at equilibrium, the infiltrated body is 60% vol solid.
- the Cr is the same in the target, skeleton and infiltrant.
- the amounts of carbon vary between the target, skeleton and infiltrant, and the amounts of iron also differ between the target, skeleton and infiltrant, because the amount of iron is simply the balance of the remaining material in each.
- the foregoing method uses the same concentration of the non-MPD element, in this case, Cr, in the infiltrant and the skeleton as is in the target composition, in this case, 12% wt.
- a method in general, is referred to herein as a basic style method.
- Other styles of methods referred to as near tie-line, off tie-line and reverse slope styles) are also explored below.
- some or all of the non-MPD elements are also varied between skeleton and infiltrant to achieve a target composition.
- the amount of the base material, iron is also varied, although not explicitly mentioned, by the fact that iron makes up the balance of each composition.
- D2 is a conventional, hardenable tool steel, often used in dies for use below 300 °C (for instance in plastic molding) . It has a composition specified as follows. In the above simplified examples the target C, Cr and Fe concentrations fall within the specification for D2.
- D2 Compositions have been studied, for two reasons, among others. The first is to study an alloy that is chemically identical to a conventional tool material. The second is to understand and minimize erosion during infiltration, which can occur and has been observed using the basic style method. ⁇
- a primary reason that erosion occurs is that even if the phase fractions of skeleton and infiltrant are the same as the equilibrium solid and liquid phase fractions at the infiltration temperature, if their compositions are not at equilibrium with each other, then dissolution and reprecipitation reactions can occur.
- Fig. 3 is a phase diagram for a D2 system, having bulk composition of 12% wt Cr, 1% wt Mo and 1% wt V, as set forth in the Table D, below, at the row designated target.
- a composite having the bulk composition of D2 will be 60% solid and 40% liquid at 1306 "C.
- This can be determined using phase diagrams or software such as Thermo Calc.
- the Cr values are not shown in Fig. 3, but are shown on Fig. 4, discussed below.
- V L 40% 2.63 15.73 0.5 1.72 0.19 0.328 1.88 77.02
- Vs 60% 0.823 9.76 0.34 0.567 0.259 0.443 0.475 87.33
- Erosion can be minimized mechanically by noting that most erosion occurs near to the in-gate.
- providing a sacrificial region, such as stilts, as discussed in U.S. Patent No. 5,775,402, issued on July 7, 1998, adjacent the in- gate can reduce erosion damage to the principal part being made. It is also possible to reduce erosion by adjusting the composition of the skeleton and the infiltrant so that they are closer to being at equilibrium at the infiltration temperature with each other.
- Fig. 4 is an isothermal phase diagram for the Fe-Cr-C-Mo-V system (generated using software such as described above) , applicable to D2 tool steel, and helps illustrate the procedure. It is a two-dimensional slice of a many-dimensional construct. The relevant temperature is again 1306°C (1579 K) . Molybdenum (Mo) and Vanadium (V) are both present at 1% wt.
- MPD e.g. C
- non-MPD e.g. Cr, Mo, V
- Fig. 4 illustrates four different, but related ways to choose the compositions of a skeleton and an infiltrant to achieve a given target. These four ways delineate rough boundaries around a spectrum of workable compositions.
- the point T represents a target composition of D2 in the two-phase (liquid + austenite) field with 12% wt Cr, and 1.5% wt C.
- the points KA and IA are skeleton and infiltrant compositions, respectively, as would be chosen as discussed above according to the basic method.
- the Table D sets forth all the compositions and others to be mentioned below.
- compositions KA and IA represent the basic method and may experience erosion at the in-gate, as discussed above .
- the points S and L are on a line called a tie-line, which is a line (shown as dotted) that joins the equilibrium solid and equilibrium liquid compositions. Any composition on the line between the two points S and L will be composed of a solid having composition S and a liquid having composition L in amounts that may be found by the lever rule .
- the S and L points do not appear to be precisely on the nearby liquidus and solidus curves (so labeled) , as shown, because of the presence of Mo and V in the system.
- the diagram is drawn at constant Mo and V (1% wt each) , but the equilibrium concentrations of Mo and V are lower in the solid and higher in the liquid.
- the apparent discrepancy is due to viewing a two dimensional slice of a multi-dimensional system.
- the liquidus and solidus lines are actually surfaces, of which the locations S and L are intersections of the surfaces and the plane at 1% wt Mo and V.
- the true tie-line is out of plane of the diagram by a small amount.
- a similar comment could be made regarding most of the other multi-component phase diagrams included herein.
- liquidus and solidus compositions would be at chemical equilibrium with each other at the infiltration temperatures and thus, no erosion would occur if they were used for the infiltrant and skeleton compositions, respectively.
- the carbon concentration at that composition is the maximum carbon concentration in the skeleton. Any temperature overshoot during heating above the designated infiltration temperature will cause the skeleton to partially melt.
- the carbon concentration at that composition is the minimum carbon concentration in the infiltrant.
- T SAFE This difference in carbon concentration between the skeleton and the equilibrium solid results in the solidus temperature of the skeleton being higher by some amount than the temperature T PF .
- the temperature difference amount is referred to herein as T SAFE .
- T SAFE can be any amount, depending on the accuracy of process controls, or even zero. However, typically 50 ⁇ T SAFE and 100.
- the pair of compositions KB and IB in Fig. 4 are similar in Cr content to the compositions S and L respectively, but differ in C content, to give these greater difference in melting points.
- the C concentration for KB is 0.3%, which is less than that for S, which is 0.82%.
- the C concentration for IB is 3.5%, which is more than that for L, which is 2.6%.
- the Cr concentration in the infiltrant is 15.73% wt, and in the skeleton is 9.76% wt.
- the concentrations of other major alloying elements, Mo and V are also adjusted along the tie line between the points S and L, similar to the adjustment of the Cr composition.
- the skeleton contains 0.57 wt% Mo and 0.48 wt% V and the infiltrant contains 1.72 wt% Mo and 1.88 wt% V.
- This second style is referred to herein as a near tie-line method, because it uses compositions that lie on a line KB-T-IB (from KB to IB) , near to the line that ties the equilibrium compositions L and S to the target composition T, in this case for D2. They are not on the tie- line STL, because the carbon amounts are adjusted, as discussed above, to prevent slumping and clogging.
- the general properties of > the near tie-line style pair of compositions are that: they lie on a line that passes through the target composition T; they have non-MPD (in this case, Cr, Mo, V) concentration equal to that of the equilibrium solid and liquid compositions, they have MPD (in this case, C) concentrations equal to that of a basic case, and using the lever rule, they would result in a bulk composition of T, present in a liquid and a solid phase in the ratio specified, in this case 60% vol sol.
- non-MPD in this case, Cr, Mo, V
- MPD in this case, C
- a potential draw back to this near tie-line style method is that it may result in fairly large differences in non-MPD element concentration, e.g. Cr, in the infiltrated body, comparing the regions that had been skeleton with those that had been infiltrated voids. Heat treatment may not homogenize the material, since the skeletal region and solidified infiltrant region are already nearly at chemical equilibrium with each other at the homogenization or austenitization temperature.
- non-MPD element concentration e.g. Cr
- a third method style is to use a pair of compositions with Cr concentration part way between the two extremes of the basic (IA and KA) and the near tie-line (IB and KB) concentrations.
- This is an off-tie-line style method, given by IC and KC in the Fig. 4.
- the Cr concentration in the skeleton and infiltrant is about halfway (the average) between that of the other two cases.
- the skeleton material will be less susceptible to erosion than with the basic style method, and there will typically not be as noticeable differences in microstructure between the originally skeletal and solidified infiltrant regions that a typical near tie-line style method would produce.
- the off tie-line style can be thought of as a mixture of the basic and near tie-line styles, and can be described mathematically using a parameter R n , where 0 ⁇ R n ⁇ 1.
- the skeleton composition for each non-MPD element, n can be found using the relationship:
- R-. 0.5 is often used herein, however, all values 0 ⁇ R__ ⁇ 1 are contemplated as within inventions disclosed and described herein.
- the region 0TL K in which skeleton compositions reside, is further roughly bound by the solidus, with consideration for T ⁇ AFE , as discussed below.
- the low wt% C boundary for OTL K is either 0% C or that amount of C which requires a high amount of carbon that produces carbide stability in a complementary infiltrant.
- a low carbon boundary is shown in Fig. 11, at curve 1102. Note that infiltrant composition IB is in a liquid + M7C3 (carbide) field.
- the skeleton composition point KB is complementary to the composition IB. Thus, it is outside of the boundary 1102, above which carbon concentrations are high enough to avoid this problem.
- Mn.I Mn. + R * (Mn. " . T ) (Eq. 2) [00101] Where R ⁇ is the same R_. as used to find the skeleton composition.
- the region O Lj is further roughly bound on the low MPD side, by the liquidus.
- the boundary for OTLj on the high MPD side is defined by keeping the infiltrant composition in a one phase liquid field.
- a fourth method style is a reverse slope method, for example pair KD, ID in Fig. 4.
- the concentration of the non MPD elements in the skeleton is between that of the target value and the equilbrium liquid value at L.
- the concentration of the non-MPD element in the infiltrant is between the target value and the equilbrium solid value at S.
- This reverse slope approach has at least one potential advantage.
- the homogeneity of the body will be no better than the basic case, however the morphology, or distribution, of the carbides may be different than any other case. Because there is more Cr in the skeleton than in the infiltrant, there is a large driving force to move carbon from the infiltrant to the skeleton.
- a consequence of this reverse slope style of method is that the amount of carbon in the skeleton must be severely reduced (0.13 w%) , and correspondingly increased in the liquid (3.79%) in order to maintain a temperature margin (T SAFE ) between the infiltration temperature and the temperature at which the skeleton begins to soften.
- T SAFE temperature margin
- the biggest draw back to this style is that erosion may be difficult to control, since the skeleton and liquid are far from their equilibrium values. However, if large particle sizes are used, satisfactory results might be possible. In general there is little added concern that carbides will form in the infiltrant at the infiltration temperature because strong carbide forming elements have been removed from the liquid.
- the reverse slope style is the easiest to perform. Given a low wt% C starting powder (also used for the skeleton) , one may simply add an appropriate amount of carbon to obtain an infiltrant of just slight reverse slope style. This occurs because the amounts of all other elements are diluted with the carbon addition.
- the MPD element in the skeleton is bound on the high side by the solidus, with regards to T ⁇ AFE , and on the low side either by 0 or that amount of MPD which moves the complementary infiltrant liquid into a two-phase field.
- skeleton and infiltrant pairs may also be considered in an extreme slope style, as shown by pair IE, KE in Fig. 5 which would result from using a factor like R, having an absolute value >1.
- This pair has far from equal amounts of non-MPD elements in the skeleton and liquid.
- This method has far from equal amounts of non-MPD elements in the skeleton and liquid.
- the slow diffusing, non MPD elements might have large gradients within the part after infiltration, leading to very long homogenization times.
- Third, the likelihood of having carbide stability in the liquid increases as more strong carbide forming elements (Cr, Mo, V, W) are added to the liquid.
- the foregoing four general technique styles each identify a skeleton and an infiltrant pair of compositions, relative to a target composition that has been labeled T. These four methods describe pairs that are likely to result, to varying degrees, in successful and useful combinations.
- the infiltrant composition has been labeled IA
- the skeleton composition has been labeled KA.
- the skeleton and infiltrant compositions KA and IA are designated as complementary with respect to a target composition T. In specific, they are complementary in a basic mode.
- the skeleton and infiltrant compositions labeled KB and IB are complementary with respect to the target composition T, and, in specific, they are complementary in a near tie-line mode.
- the skeleton and infiltrant compositions labeled KC and IC are complementary with respect to the target composition T, and, in specific, they are complementary in an off tie-line mode.
- the skeleton and infiltrant compositions labeled KD and ID are complementary with respect to the target composition T, and, in specific, they are complementary in a ⁇ reverse slope mode.
- complementary pairs of skeleton and infiltrant compositions KX and IX include any pair that lie an a line in the shaded region of a phase diagram, such as Fig. 4, that passes through the target composition T, and which are set at compositions such that, given a packing fraction V PF of the skeleton, a bulk composition made up of a liquid phase and a solid phase having compositions of IX and KX, respectively, of appropriate masses, would result in a bulk composition of T, according to known application of metallurgical analytical techniques, including the lever rule (rule of mixtures) . See Physical Metallurgy, Cahn, et al .
- any complementary pair as defined herein will result in the bulk composition of the target. What will vary, is the degree to which a final infiltrated body is homogeneous with respect to non-MPD elements, and, the degree to which the skeleton is susceptible to erosion. Generally, complementary pairs that result in a more homogeneous end product are more susceptible to skeleton erosion.
- a complementary pair can be described by an expression such as Eqs. 1 and 2, with -1 ⁇ R ⁇ 1, then such a pair is complementary in a mode that is between a near tie-line mode and a reverse slope mode. If the pair can be defined by such expressions with 0 ⁇ R ⁇ 1, then the mode is complementary in a mode that is between a basic mode and a near tie-line mode.
- the other concentrations and parameters are set forth in Table F, below, where the concentrations of Mn( ), Si( ⁇ ) and Ni ( ⁇ ) are small, and do not vary from composition to composition.
- the carbon level of all three skeleton alloys is about 0.35% wt C, and the three infiltrants are at 3.25% wt C. Comparison of the three alloys to each other and to conventional wrought D2 were made .
- Ingots of the three alloys described in Table F were fabricated.
- controlled porous geometries were created using wire-EDM. Basically, a rectangular block, 27 x 13.5 x 12.5 mm was EDM machined to leave parallel, upstanding square cross-section columns. The spacing of the columns and wire kerf is such that 60% of the material remains while 40% is removed, similar to the packing fraction of powder in powder beds .
- the column spacings are about 1.2 mm on centers. Each is a square with a side of 0.92 mm.
- the Vickers microhardness of the martensite after the austenitizing treat and water quench was measured in three locations , the skeleton, the Cr-poor region immediately around the skeleton, and the area of eutectic martensite + carbide in the infiltrated regions.
- the hardness values converted to Rockwell C hardness of the samples after infiltrating were 57, 50 and 54 respectively and after austenitizing and quenching treatment 66, 63, and 62 respectively. So the skeleton region has the hardest martensite, while the eutectic martensite is softest, but still quite hard.
- the intermediate, or off tie line sample exhibited very little erosion and was less homogeneous than the basic method sample. Again, samples were fully infiltrated with a density approaching 100% of wrought D2. The erosion evidence was intermediate between the basic and near tie line cases, no visible rounding of columns, but they lacked a sharp edge. No cracks were seen in the sections, nor was carbide growth in the skeleton observed. Again, a Cr poor region of solidified infiltrant surrounding the skeleton was observed. The hardness values, converted to Rockwell C, of the skeleton, Cr- poor and eutectic regions after infiltrating were 56, 54 and 38 respectively and after austenitizing and quenching were 68, 63.5 and 67.5 respectively. The infiltrated samples were quite non-uniform in hardness between different regions, but the austenitized and quenched samples were quite uniform, and were, in fact, harder than the basic case in all instances.
- D2 a major reason for inhomogeneity in the D2 type example is the difference in the concentration of Cr between the infiltrant and the skeleton.
- Cr is a strong carbide former.
- D2 has about 12% wt Cr in the target composition, with about 9.76% in the skeleton, and 15.73% in the infiltrant, for the above described near tie-line example.
- A3 which do not have as high a concentration of carbide formers (5.15% wt Cr in the target) such that the difference between the skeleton (4.45%) and infiltrant (6.29%) regions would not be as significant for the near tie line case.
- a certain solubility of the MPD element into the main skeletal metal is required for at least some homogenization of the material after infiltration.
- Shown in Fig. 6 is a hypothetical phase diagram showing temperature vs % wt Carbon for a generic iron based alloy.
- the target composition of the material after infiltration is 1.5% wt C, as shown by point M C ⁇ T .
- M c _ max is the maximum solubility of carbon in the metal at the eutectic temperature, as shown about 1.75%.
- the infiltration temperature is chosen as 1335 °C (1608 K) , which is, in this case, the temperature where 60% vol of the material is solid.
- the solidus and liquidus compositions are M cs (1.075% wt C) and M ⁇ (2.15% wt C) respectively.
- the target alloy contains a slight excess of carbon, so that the concentration of the carbon in the target is greater than the maximum solubility, but still less than a somewhat arbitrary multiple Z of the maximum solubility,
- a typically useful degree of homogeneity can be obtained.
- Fig. 8 shows using boron instead of carbon as the MPD.
- M BrK 0
- M B/T 0.88% wt
- M B _ max 0.05% wt
- M E/S 0.03% wt
- M B ⁇ L 2.15% wt
- M B ⁇ I 2.19% wt .
- M B . max ⁇ 2* M B _ T To achieve this condition, the temperature must be increased to 1525 °C (1798 K) , which is only 25°C less than the melting point with no B. This would be an unacceptably high infiltration temperature.
- the maximum MPD concentration in a target alloy for a given system can be found by using the lever rule, the eutectic temperature and concentration of MPD at the eutectic (M MPD . eu ) , the maximum solubility of the MPD in the base metal (M MPD _ max ) , and the minimum mass% of solid (M s _ min ) that can be allowed in the solid-liquid two-phase product that affords sufficient strength, typically 50%.
- MPD -max,T M MPD _ eu - (M s _ min / 1 U 0 ) (M MPD _ eu — M MPD _ ma ⁇ . Eq . D )
- Targets having MPD concentrations less than M ⁇ . ⁇ ⁇ can be made at higher temperatures, while targets having greater MPD concentrations than M MPD _ eU/T can not be made at that amount of equilibrium solid.
- targets having greater MPD concentrations than M MPD _ eU/T can not be made at that amount of equilibrium solid.
- M MPD - max M MPD , L - (M s . min / 100 ) * (M MPD
- Fig. 20 shows a phase diagram with lines of equal mole % solid in the Fe-12wt% Cr-C system for 90, 80, 70, l 60 and 50 mole % solid over the entire two phase (liquid + FCC) region.
- vol % is nearly equal to mole %.
- the carbide-liquid solvus line noted in the figure. The intersection of this line and any of the constant mole% lines, defines the maximum carbon content present in the target composition.
- Chromium is present in many steels in moderate amounts (up to 25%) , however, it has very little effect as an MPD and so is not a viable candidate. Molybdenum has more MPD effect than Chromium, but is typically only present in much smaller amounts in steel and so again is not a viable candidate.
- viable candidates are carbon, silicon, manganese (Mn) and nickel (Ni) .
- the respective diffusivities of these 4 elements in iron at 1100°C are 5.6 x 10 "11 , 2.4 x 10 " 13 , 1.8 x 10 "15 , 3.4 x 10 "16 (all m 2 /s) .
- carbon and silicon are distinctly higher in diffusivity than the other two candidates, Ni and Mn.
- Mn which is faster diffusing than Ni
- a numerical diffusion model has been run with a particle diameter of 50 microns and a packing fraction of 60%. After homogenization for 15 hours at 1100°C this system would still have a concentration variation between particle center and infiltrant that was 25% of the starting variation. The use of Ni would lead to even more variation for the same homogenization treatment. These times will often make these candidates impractical choices.
- a useful metric for choosing candidate MPDs must consider not only the diffusivity of the MPD, but also the diameter of the particles in the skeleton.
- a useful ratio, where L is the diameter of the particle and D is the diffusivity of the diffusing element is :
- Fig. 9 in two parts, A and B
- Fig. 9 an overview flow chart which shows the steps used for a basic style method with one MPD element, as discussed above. Further, the steps used for the near tie-line, off tie-line, and reverse slope style methods, both with one and two MPD elements, are also shown in Fig. 9, and will be discussed below.
- a general metal system such as D2 , A3, Fe-C, etc. is chosen. This choice also necessitates choosing a final target bulk composition, including the mass% of the constituent elements. The mass% is equal to the weight%, both of which terms may be used interchangeable herein.
- V PF a volume % of items. This selection is principally based on the type of particulate material and the requirements of the manufacturing process being used, such as three-dimensional printing, metal injection molding, selective laser sintering, or die pressing.
- the operator determines 904 a temperature T PF where the target composition will have the same vol% solid as the packing fraction of the skeleton, and a liquid volume equal to the void fraction of the skeleton. (This is not the same as another temperature discussed below, T ⁇ s , the skeleton solidus, the temperature above which the original skeleton composition would soften.)
- T PF a temperature where the target composition will have the same vol% solid as the packing fraction of the skeleton, and a liquid volume equal to the void fraction of the skeleton. (This is not the same as another temperature discussed below, T ⁇ s , the skeleton solidus, the temperature above which the original skeleton composition would soften.)
- the tie-line composition of the solid of each element M M ⁇ S etc) and liquid are determined 906 at T PF , as well as the mass % of the entire solid and liquid phases, M s and M L .
- step 910 the operator assigns parameter R, which will control the amounts of non-MPD elements that are present in the skeleton.
- the operator may chose a different R for each non-MPD element (as discussed below) . The effect of assigning different values for parameter R is discussed below.
- the operator calculates 912 the mass% of each non- MPD element, e.g. Cr, in the skeleton using a specific instance of Eq. 1 above, the relation:
- the operator also calculates 912 the mass% of each non-MPD element, e.g. Cr, in the infiltrant using a specific instance of Eq. 2 above, the relation:
- M cr .i M cr, ⁇ + (M cr , ⁇ - M ⁇ /M ⁇ (Eq. 9)
- the mass% of the non-MPD elements in the skeleton and in the infiltrant are the same as the mass% in the target. Note that it would also be reasonable to develop similar relations for the infiltrant compositions using the R factor. However, it is not necessary to do so, because the R factor is implicitly used in the infiltrant relation Eq. 9, because it is based on the skeleton composition M Cr _ K , which was developed with relation Eq. 8, which does include the R factor.
- step 920 a temperature T SAFE is chosen. Typically, 50 ⁇ T SAFE ⁇ 100 for steels. This is how much temperature difference there will be between T PF and the solidus temperature of the skeleton T ⁇ s , which is found in step 922 below.
- the mass% of the MPD (carbon) in the skeleton 924 is calculated at T ⁇ s given the amounts of the non-MPD elements found in step 912 above.
- the skeleton is completely defined in terms of it's composition and mass% and vol%. The amount of iron in the skeleton may be found by adding up the mass% of all the elements and subtracting from 100%.
- the amount of MPD to be in the liquid M c ⁇ 1 is determined 926 by applying the relation:
- This relation is based on comparing the amount of MPD in the target and the skeleton, and making up the deficit by an excess in the infiltrant.
- the operator decides 928 how much ⁇ v (if any) isothermal solidification will take place during infiltration.
- the maximum possible amount of isothermal solidification is the void fraction V VF of the skeleton.
- V VF the void fraction of the skeleton.
- the operator finds 930 V s , the equilibrium solid volume fraction after infiltration by applying the relation
- V s V ⁇ + ⁇ V. (Eq. 11)
- T INFIL is the temperature at which the target composition has a solid volume fraction of V s .
- the operator 934 determines the liquidus temperature T IL of the infiltrant and checks 936 to be sure that T IL ⁇ T Infil . This ensures that the infiltrant is truly all liquid. If this is true, then the process of determining parameters is complete 938. Otherwise, the process returns and the operator may elect 940 to change one or more conditions or parameters to try to obtain better infiltration conditions without carbide stability in the liquid.
- step 914 the operator proceeds to 916, and assigns, for the second MPD element, a parameter, such as, for Silicon, P SI , where 0 ⁇ P si ⁇ l/3.
- a parameter such as, for Silicon, P SI , where 0 ⁇ P si ⁇ l/3.
- the operator determines the mass% of the second MPD, e.g. Si, in the skeleton, using the relation:
- Fig. 17 is a phase diagram for D2 , showing the effect of varying T SAFE on the composition of skeleton and infiltrant pairs.
- the infiltration temperature is 1552 K, which results in 70% vol solid and 30% vol liquid.
- the skeleton can tolerate more carbon, with a smaller T SAFE .
- relatively larger T SAFE results in the point KA moving toward lower C concentration
- relatively smaller T SAFE results in the point KA moving toward relatively higher C concentration, limited by the C concentration on the solidus line at the Cr concentration of the target composition.
- Fig. 9 shows the steps that are used to determine basic mode complementary infiltrant and skeleton pairs relative to a target bulk composition, for the basic style of a method of the invention.
- Fig. 9 also shows the steps that are used to determine near tie-line mode complementary pairs if the near tie-line style method is used.
- the method steps are similar to the basic style method, except that the operator chooses a different value for R in step 910B.
- the concentration of the non-MPD elements such as Cr, Mo, etc.
- the concentration of the non-MPD elements are set to different values than in the basic style method, because the R parameter equals 1, and not 0.
- M Cr;K is set to equal the concentration of Cr in the equilibrium solid M Cr/S .
- the concentration of Cr in the infiltrant M Cr/I is set to equal the concentration of Cr in the equilibrium liquid composition M Cr;L . So, the concentration of Cr in the skeleton and in the infiltrant differ from each other, and also, differ from the concentration of Cr in the target, M CrT .
- the basic style method all these Cr concentrations are equal.
- the remaining steps for the tie-line style method are the same as the corresponding steps for the basic style method.
- Fig. 9 shows the steps that are used. Again, the only difference is step 910C as discussed here.
- the steps of both the basic and the near tie line techniques are conducted to determine the amount of non-MPD that the skeleton should have as above for both techniques. Then, the amount of non-MPD in the skeleton for the off-tie-line style is taken to be somewhere in between these two concentrations . Once the skeleton concentration is determined, the infiltrant concentration of MPD and non-MPD elements is determined as complementary in the same manner as was done for the near tie line technique.
- off tie-line pairs there are an infinite number of off tie-line pairs that might be used, as discussed above, depending on how near to the basic style or near tie-line style, the operator chooses to be.
- one way to choose the off tie-line parameters is for each non-MPD element n, such as Cr, Mo, V etc., (in the D2 case) to assign 912C a parameter R n , such as R Cr , R Mo , etc.
- the R-. parameter is used to calculate 912 the concentration of the non-MPD element in the skeleton and the infiltrant.
- concentrations of Cr in the skeleton, M CrK using the same relation (Eq. 8) as discussed above for the other styles) is again given as:
- Fig. 9 also shows the steps that are used. Again, the only difference is step 910D as discussed here.
- Mcr.i Mc r . ⁇ + ⁇ M cr, ⁇ - M Cr , K ) /M x . ( Eq . 9)
- Minus 1 was chosen only because it simplifies explanation, and also because it is not likely that an operator would use an R factor with a significantly larger absolute value. However, setting -1 as the lower bound is arbitrary.
- a skeleton composition driven process generally, it may be convenient to pick a skeleton composition first because the availability of custom powders is more limited than that of custom infiltrants, and, setting infiltration temperatures over wide ranges is generally routine.
- Fig. 10 outlines steps a designer and operator would follow for a skeleton driven process.
- the nomenclature used in the skeleton driven flowchart, Fig. 10, is the same as that used for the packing fraction driven flowchart, Fig. 9.
- the operator first chooses a target composition in step 1000 by selecting the target weight percentages of the elements in the target alloy, M C ⁇ T ; M Cr;T ; M Mo#T ; etc.
- step 1002 the operator chooses the skeleton composition, M c# ⁇ ; M CrK ; M Mo _ K ; etc.
- these values may be chosen to be equal to the respective target values, which results in a basic style of infiltration. Or, they may be chosen as some other value (for example a pre-made powder that is close to the target composition, but varies slightly in one or more non-MPD elements, and has a lower concentration of the MPD element than the target) , which would result, probably, in an off-tie line or reverse slope style method.
- the operator determines, through calculation or experimentation (for example differential scanning calorimetry) the solidus temperature of the skeleton powder.
- T SAFE for the skeleton, where typically 50 °C ⁇ T SAFE ⁇ 100 °C.
- step 1008 the operator determines the packing fraction of the skeleton powder that results from whichever manufacturing method is chosen to form the skeleton (for instance, 3D-printing, Selective Laser Sintering, Fused Deposition Modeling, Laminated Object Manufacturing, Metal Injection Molding, or die-pressing).
- step 1010 the operator finds T PF , the temperature where the target composition has the same volume fraction solid (V s ) as the packing fraction of the skeleton (V PF ) , with the remaining target composition being liquid.
- step 1012 The operator tests if T ⁇ s > T SAPE + T PF in step 1012. If yes, the process continues to step 1014, otherwise, the process goes to step 1028, where the operator may choose different values of V PF , T SApE or the skeleton composition. If using a pre-existing powder, the operator will likely have limited control over the skeleton composition, perhaps only being able to adjust the carbon concentration by decarburizing it. A person skilled in the art of the manufacturing process (of the skeleton object)' may be able to slightly adjust V PF by changing processing parameters of that process. Or V PP may be altered slightly by sieving the powder appropriately before making the skeleton. The process returns to step 1002 if changes are made .
- step 1014 the operator finds the infiltrant composition of each element (MPD and non MPD) by using the expression Eq. 10 as above, which is repeated here:
- M c ⁇ M c, ⁇ + ( M c, ⁇ - M c, ⁇ )/ M _- (Eq. 10)
- step 1016 the operator determines the liquidus temperature of the infiltrant, T IL .
- step 1018 the operator decides on how much material will solidify during infiltration, ⁇ V. Then the volume solid (V s ) present after infiltration and partial solidification is determined in step 1020. Then the operator determines the infiltration temperature (T IL ) where the amount of solid at equilibrium is equal to V s , step 1022.
- step 1024 the operator compares T IL to T INFIL . If T IL ⁇ T. nfil , then the process is complete, 1026. Otherwise, the process goes to step 1030, where the operator may elect to change ⁇ V, V pF , T SAPE , or the skeleton composition.
- the operator has more opportunity to affect the solidus temperature of the skeleton than in the skeleton composition driven method, shown in Fig. 10.
- the act of successfully selecting the skeleton composition, particularly the MPD elements may initially require iteration until the operator acquires experience with the particular process.
- the resulting style of infiltration (basic, near tie line, etc.) is not necessarily immediately evident in the skeleton composition driven method, although a designer will develop a feel for how different elements behave in regard to their solid/liquid/target compositions, and how close the skeleton and infiltrant compositions chosen are to any one of the four method styles .
- phase diagrams of the types shown in Figs . 3 and 4 are available that cover the approximate range of target, skeleton and infiltrant, then these will aid in choosing a skeleton without having a selected packing fraction.
- any designer may opt to use both flow charts. If designing a system from the start, and knowing an approximate V PF that is likely to be obtained by the skeleton manufacturing process, the designer can use the volume fraction driven method, illustrated in Fig. 9, to find a suitable skeleton composition and develop a specification (with it's own range of allowable compositions) to provide to a powder manufacturer. Once the powder is made, the designer can use the skeleton composition driven method, shown in Fig. 10, to account for variations both in the skeleton composition, and in the packing fraction of the powder, to obtain the desired target value by designing an appropriate infiltrant, since the infiltrant is the easiest component to adjust.
- step 910B near tie-line
- step 910D off tie-line
- the MPD concentrations in the skeleton differ, with the lowest concentration being for the basic mode, and the highest concentration being for the near tie-line mode.
- steps 922 and 924 allows the designer to choose a skeleton having a higher concentration of MPD, while still being sure that the actual solidus of the skeleton composition is at least T SAFE degrees greater than the infiltration temperature. If the designer can tolerate a larger concentration of MPD in the skeleton, then the system requires a lower concentration of MPD in the infiltrant.
- the near tie-line MPD skeleton concentration KA could be anywhere along the line KB SAFE to a lower limit as discussed above. Consequently, a complementary near tie-line MPD infiltrant concentration can be along the line IB SAFE at a location that is complementary to the skeleton MPD concentration.
- the endpoints KB and IB can lie along the lines KB SAPE and IB ⁇ AFE respectively, with the lower extreme of the skeleton concentration and the higher extreme of the infiltrant concentration being governed by conditions already discussed.
- Example tables El - E16 will also provide an infiltrated skeleton such that, at equilibrium, a solid and a sufficiently large, liquid phase persists, thereby allowing full infiltration, and subsequent partial homogenization by diffusion.
- the degree of homogenization is addressed in a section below.
- a system having 60% volume solid, 40% volume liquid at equilibrium is used.
- the equilibrium and infiltration temperature in degrees K is T 401ig , which is the same as T 60sol , as used above. This is the temperature at which a target having the bulk composition as desired will be 60% vol solid and 40% vol.
- T 70sol the relevant infiltration temperature
- the solid/liquid volume ratio is 60/40. Other ratios are also important for different calculations, and they are not the same as the volume ratios, nor are they the same as each other.
- the mole percent liquid and solid values are given, as are the weight percent liquid and solid values.
- the packing fraction of the skeleton, except where noted, is 60% vol solid, with a void fraction of 40% vol void.
- the temperature T ⁇ s is the skeleton solidus temperature in degrees K, which should be between 50 and 100 degrees K higher than the infiltration temperature T 401iq .
- the wt% C at the skeleton solidus temperature is also given separately in the row designated with the alloy name, under the column wt%C@T KS . For instance, for the alloy D2 , it is 0.3.
- Target The target composition is given in the row entitled Target. This is the bulk composition of the final, infiltrated product. If the product could achieve complete homogenization, this would be its composition throughout.
- the composition of the skeleton is given in the row entitled Skeleton B.
- the composition of the infiltrant is given in the row entitled Infiltrant B.
- the concentration of C (MPD) in the skeleton B equals the concentration of MPD in the skeleton in the basic style skeleton A.
- the carbon concentration in the infiltant B equals that in the basic style, Infiltrant A.
- the concentrations of the major non-MPD element, Cr follow a different pattern.
- the Cr concentration equals the Cr concentration in the 60% Solid, equilibrium composition.
- the Cr concentration in the Infiltrant B is the same as the concentration of Cr in the 40% Liquid equilibrium composition.
- the composition of the skeleton is given in the row Skeleton C, and the infiltrant is given in the row Infiltrant C.
- C (MPD) concentrations in the Skeleton is equal to the C concentration in the skeletons for both the basic and near tie-line styles, while the Cr (non-MPD) concentration is between the Cr concentrations for the same two skeletons.
- the complementary Infiltrant C concentration is equal to the C concentrations for the other two styles, while the Cr composition is in between them.
- V L 40% 2.63 15.73 0.50 1.72 0.19 0.33 1.88 77.02
- V s 60 % 0.82 9.76 0.34 0.57 0.21 0.44 0.48 87.38 basic:
- V L 40% 1.82 4.96 0.31 7.64 0.17 0.24 3.26 8.98 72.63
- V s 60 % 0.47 3.63 0.26 3.29 0.22 0.37 1.18 4.29 86.28 basic:
- V L 40% 2.00 2.43 15.15 0.87 79.56
- V s 60 % 0.70 1.73 11.25 0.76 85.57 basic:
- V 40% 0.80 5.73 0.42 1.80 0.22 1.16 1.31 88.57
- V s 60 % 0.10 4.78 0.28 1.18 0.19 0.90 0.81 91.77 basic:
- Target Range 0.40 - 0.50 1.2 - 1.5 1.2 - 1.5 0.3 - 0.5 2.0 - 2.5 0.2 - 0.4 balance
- V u 40% 0.80 1.49 1.67 0.55 2.74 0.35 92.41
- V s 60 % 0.23 1.26 1.15 0.31 1.94 0.19 94.93 basic:
- V L 40% 2.10 6.29 0.63 1.88 0.20 0.27 1.89 86.75
- V s 60 % 0.72 4.45 0.42 0.70 0.20 0.24 0.61 92.66 basic:
- V L 40% 1.64 14.58 1.24 1.16 81.38
- V s 60 % 0.60 10.40 0.81 0.90 87.29 basic:
- V L 40% 2.37 15.45 82.18
- V s 60 % 0.97 9.95 89.08 basic:
- V L 40% 1.49 5.00 0.33 0.99 0.17 0.24 3.28 19.29 4.69 69.22
- V s 60 % 0.35 3.56 0.28 0.51 0.22 0.26 1.34 10.58 5.62 82.90 basic infiltrant - A 1.95 4.13 . 0.30 0.70 0.20 0.30 2.10 14.00 5.25 76.32 skeleton - A 0.06 4.13 0.30 0.70 0.20 0.30 2.10 14.00 5.25 78.22 near tie-line: ⁇
- V L 30% 3.03 17.20 0.52 2.00 0.18 0.25 2.30 74.52
- V s 70 % 0.92 10.00 0.36 0.62 0.21 0.46 0.50 86.95 basic:
- V s 70 % 0.81 4.54 0.44 0.76 0.20 0.25 0.66 92.34 basic:
- the target composition includes N basic elements in addition to iron, E l f E 2 , ... E N , where N ⁇ l. It is noted here that although the individual elements of the set are noted by their subscripts as being number 1 of the set, number 2 of the set, etc., up to number N of the set, where N ⁇ l, N may be equal to exactly 1, and need not equal 2, or 3 , even though the elements E 2 , ... E N are indicated as elements of the set. This convention is merely used to indicate a set with a number N of elements. The only requirement is that N ⁇ l, as specified. The same is also intended with respect to the skeleton and infiltrant compositions.
- the foregoing examples show an exemplary member of a broad family, with possible variations along several different dimensions.
- the foregoing examples are all based on 40% volume liquid at equilibrium except as noted in Example E15 D2 and E16 A3.
- systems with as little as 7% volume liquid remaining at equilibrium can be made to fully infiltrate. The less liquid remaining, the more precise process controls must be.
- the volume percentage of liquid at equilibrium can vary. This would change the relative amounts of the other elements in the target composition, and thus, the skeleton and infiltrant.
- a typical range is between about 20% volume liquid and about 40% by volume liquid.
- Example table E15 shows the parameters involved in infiltrating a skeleton that is 70% vol solid initially, to achieve an equilibrium solid that is 70% vol solid and 30% vol liquid.
- the temperature T 3011 -. at which a D2 composition is 30% vol liquid at equilibrium is 1552°K (1279°C) (as compared to higher 1579°K for 40% vol liquid.
- the composition of the target is identical for all components as for D2 with a 40% vol liquid at equilibrium.
- the compositions for the Skeleton, Target, Infiltrant, and Equilibrium Liquid and Solid entities for both the 40% liquid at equilibrium and the 30% liquid at equilibrium are shown in Fig. 3, with those for the 40% liquid being shown as points at 1306°C and those for the 30% liquid case being shown as points at 1279°C.
- the 70% solid composition point S at 1279°C has a higher concentration of C (.915% wt) than does the 60% solid composition point S at 1306°C (.823% wt) and the corresponding 30% liquid composition point L at 1279°C has a higher concentration of C (3.03% wt) than does the 40% liquid composition point L at 1306°C (2.63% wt) . This is because both the solidus and the liquidus lines are sloped such that their intersections with a line of lower temperature are shifted toward higher concentrations of C.
- Example E15 Table D2 also shows the ⁇ MPD (carbon) and Chromium concentrations for a complementary skeleton and infiltrant pair for a near tie-line style method, and for an off tie line style method, as computed by assuming that the C content would be the same for each, as it is in the basic style method, and the Cr concentration would vary.
- the methods shown in Fig. 9, steps 920 and 922 strictly applying an equal T SAPE for each style, method was not used to generate the values in Example E15 Table D2.
- infiltrant and skeleton compositions are shown for the three modes of basic, near tie line and off tie line in Fig. 11, which relates wt % Cr to wt % C, at 1552°K (1279°C) . Inspection shows that using the near tie line method, the infiltrant composition IB at about 4.08% wt C lies within a two phase field of liquid and M7C3 carbide. This would probably not successfully infiltrate, due to the high potential for clogging at the in gate, It illustrates the need to conduct the step 9 36, shown in Fig. 9, to check the infiltrant liquidus temperature, and make sure that it is less than the infiltration temperature.
- D2 steel is in the so called "D" family (as established by ASTM International) .
- the D family is a high Carbon, high Chromium, cold work, tool steel.
- There are other members of the D family that are similar, but with variations in the amount of Mn, Mo, Ni, Si and V. So, a designer might use another member of the D family as a target in a similar fashion.
- the specification specifies ranges for elemental concentrations. As set forth in Table C above, the C concentration in D2 may range from 1.4% wt to 1.6% wt, and Cr may range from 11% wt to 13% wt.
- An additional dimension along which variation around the basic model described above can be had, is in the skeleton packing fraction.
- a packing fraction of 60% volume has been used (which is coincidentally the same as the typical equilibrium solid fraction used in the examples, but, need not be) .
- the packing fraction can also be different, depending on the particle shape, particle size, distribution, and method of forming the powder compact. In general, spherical particles will randomly pack to about 60% vol density. Angular or irregularly shaped particles will pack to lower densities. A lower limit of about 50% vol is practical for this application.
- Packing fractions higher ithan 60% can be obtained, if the powder is very smooth or well lubricated, if the powder has a bi- odal size distribution, or, if the compact is pressed and some deformation of the original particles occurs. Packing fractions of up to about 75% with bi-modal powders may be obtainable, even without pressing, and up to about 85% may be obtainable with pressing.
- Example E15 shows what the concentrations would be for an infiltrated skeleton that has a packing fraction of 70%, and an equilibrium product that is 70% vol solid and 30% vol liquid. To achieve this, it must be infiltrated at 1552 K (1279 °C) , which is less than the infiltration temperature of 1579 (1306°C), shown in Example El, for infiltrating a 60% packing fraction skeleton to achieve an end product of 60% vol solid.
- Fig. 12 shows, for D2 steel, skeleton and infiltrant compositions for starting with a 60% vol packing fraction skeleton, and infiltrating at a temperature that results in a 70% vol solid at equilibrium.
- the basic pair is KA-IA
- near tie-line pair is B-IB
- an off tie-line pair is KC-IC.
- the equilibrium solid is at S and liquid is at L.
- Infiltrating these pairs at 1579 K (1306 °C) would result in 60% vol solid, 40% vol liquid at equilibrium.
- Infiltration of these pairs slightly lower at 1552 K (1279 °C) results in 10% solidification, to a product at 1552 K of 70% sol as in steps 928-32.
- the phase boundaries shown are at 1552 K, the temperature that results in a 70% vol solid product. Compare this with Fig. 4, showing pairs for infiltrating a 60% packing fraction skeleton at 1579 K (1306 °C) to arrive at a 60% vol solid, and to Fig. 11, showing infiltrating a 70% vol skeleton at 1552 K (1279 °C) to arrive at a 70% vol solid product.
- the skeleton compositions shown in Fig. 12 involving solidification are further from the solidus curve than in either of the other diagrams, which indicates that the skeleton is very resistant to erosion. In fact, because of the 10% material solidifying, the skeleton strength increases during infiltration. Also, as shown in Fig.
- infiltrant IB is in a single phase region, whereas the 70/30 equilibrium infiltrant IB shown in Fig. 11 is in a two phase (L + carbide) field.
- D2 , M2 , T8 and 440C steels would likely produce end products that are less homogeneous throughout their volume than the other steels. This is because they all have the potential for forming a relatively large amount of carbides, which are not easily removed in heat treatment after infiltration. D2 and 440C have relatively high chromium contents. Chromium readily forms carbides. M2 has less chromium, but more Mo, V and W. V and W form the most heat resistant carbides in tool steels. T8 contains approximately the same Cr as M2 , but has much more W and slightly less Mo and V.
- T8 steel contains enough W such that carbides are stable even at the infiltration temperature.
- the Austenitic Manganese Grade C, 06 and S6 steels have the potential to become highly homogeneous, because both have very little chromium ( ⁇ 2%) and small amounts or none of the other carbide forming elements.
- the steels H13 and A3, have modest amounts of chromium, but not enough to significantly prevent homogenization, and thus, would fall between the other two sets of families discussed, in terms of homogenization potential.
- the cast stainless steels, CF-lOSMnN, CN-7MS and HF are also fully homogenizable because of the presence of large amounts of Ni that stabilize the austenite phase (FCC) and because of the low amounts of C, so that there is little or no tendency to form carbides .
- Fig. 18 is a phase diagram at 1568 K (1295 °C) for the Austenitic Manganese Grade C system relating weight percent manganese (Mn) to weight percent C.
- Fig. 19 is a phase diagram showing Austenitic-Mn relating temperature (°C) to weight percent C.
- a target composition T is shown, along with complementary skeleton composition K (.33% wt C) and the infiltration composition I (2.65% wt C) .
- Fig. 18 shows these same compositions (showing also the concentration of Mn at about 13% wt) for the basic style method skeleton KA and infiltrant IA. It also shows an equilibrium solid composition S of about .69% wt C and 11.2% wt Mn and an equilibrium liquid composition L of about 2% wt C and 15.13% wt C.
- the near tie-line compositions for skeleton and infiltrant would be at KB and IB respectively.
- Skeleton and infiltrant pairs along these lines are complementary with respect to T in the basic and near tie-line modes, as discussed above, and all complementary pairs lying on lines in the shaded region that pass through the target composition T would be complementary in an off tie-line mode, to differing degrees of difference from the basic and tie-line modes.
- This case illustrates complete solubility of the MPD of C in an austenite phase. This is because, as discussed above, the concentration of the MPD in the target composition, is 1.2% wt, which is less than the maximum MPD concentration M c - M of about 1.7% wt at the eutectic temperature, as shown on Fig. 19. It can be cooled to a homogeneous FCC phase at the eutectic temperature .
- Fig. 13 is phase diagram at 1624°K (1351°C) for the A3 steel system, relating weight percent chromium (Cr) to weight percent carbon (C) .
- Fig. 14 is a phase diagram showing the A3 system relating temperature (°C) to weight percent C. Showing a case of infiltration at 1351 °C to achieve a 60% solid infiltrated body, and at 1330 °C to achieve a 70% solid infiltrated body.
- a target composition T is shown, having C concentrations of 1.25% wt and with concentrations of Cr (5.15%, Mo (1.15%) V (1.1%) (all wt%) and for both the 60% solid and 70% solid cases.
- Fig. 14 shows at 1351 °C a skeleton composition K (.371% wt C) and complementary infiltrant composition I (2.67% wt C) .
- Fig. 13 shows these same compositions labeled KA, IA for the basic style method, showing also the concentration of Cr for both at 5.15% wt . It also shows an equilibrium solid composition S of about .72% wt C and 4.45% wt Cr, and an equilibrium composition L of about 2.1% wt C and 6.3% wt Cr.
- Fig. 13 was generated by assigning wt% values for the Mo and V contribution as a function of Cr. This is useful, because otherwise, the points to be shown would be far from the plane in which the tie-line along the points S-T-L lies, and thus, the S and L points would appear far from the solidus and liquidus, respectively.
- the functions used are:
- This A3 case illustrates complete dissolution of chromium carbides (M 7 C 3 and M 23 C 6 ) for reasons discussed above, because the target T Carbon wt % 1.25 ⁇ M 7 C 3 solvus line at the austenitizing temperature.
- the chromium carbides (combined M 7 C 3 andM 23 C 6 ) represent 87% by mass of the carbides at 727 °C .
- the vanadium carbide (VC) is not completely soluble, but the amounts are low, that usually its solubility is not considered as important as the chromium carbides.
- the diffusivity of V in Fe is ⁇ 100 times less than that of Cr in Fe, so the vandium carbides are much more resistant to coarsening at the austenitizing temperature.
- Example table E16 A3 shows the parameters involved in infiltrating a skeleton that is 70% vol solid initially, to achieve an equilibrium solid that is 70% vol solid and 30% vol liquid, showing these parameters in a manner analogous to that discussed above for the D2 steel and a 70% vol solid at equilibrium case.
- the temperature T L30 is 1603°K (1330°C) (as compared to 1624°K (1352°C) for 40% vol liquid.
- the composition of the target is identical for all components as for A3 with a 40% vol liquid at equilibrium.
- the compositions for the Skeleton, Target, Infiltrant, and Equilibrium Liquid and Solid entities for both the 40% liquid at equilibrium and the 30% liquid at equilibrium are shown in Fig. 14, with those for the 40% liquid being shown as points at 1351°C and those for the 30% liquid case being shown as points at 1330°C.
- the 70% solid composition points all have a higher concentration of C than do the corresponding points for the 60% solid composition for the same reasons as with the D2 case, namely, because both the solidus and the liquidus lines are sloped such that their intersections with a line of lower temperature are shifted toward higher concentrations of C.
- Example E16 Table A3 also shows the MPD (carbon) and Chromium concentrations for a complementary skeleton and infiltrant pair for a near tie-line style method, and for an off tie line style method, as computed by assuming that the C content would be the same for each, as it is in the basic style method and the Cr concentration would vary.
- the methods shown in Fig. 9 steps 920 and 922, strictly I applying an equal T SAFE for each style method was not used to generate the values in Example E16 Table A3 70/30.
- infiltrant and the skeleton compositions differ not only in the carbon content, but also in the content of the other element A.
- Carbon diffuses very quickly throughout the skeleton, and thus, significantly homogeneous end results can be obtained, despite the fact that the concentrations differ in the infiltrant portion and the skeleton portion.
- Other elements do depress the melting point, but, for various reasons, they do not diffuse throughout the skeleton as quickly as C .
- the differences in their contributions to the infiltrant and the skeleton will more significantly reduce the homogeneity of the end product.
- the foregoing has focused on carbon being a single element MPD.
- the generality of the inventions disclosed herein is not limited to single element MPDs, or to MPD that is only carbon.
- silicon (Si) can also be an, important MPD in steel ( systems.
- the diffusivity of Si in Fe at 1300 °C is about 3 x 10 "8 cmVsec, which is about .01 times the diffusivity of C in Fe (3 X 10 "6 cmVsec) , but about 100 times the diffusivity of Ni in Fe (3 X 10 "10 cmVsec) .
- Fig. 15 is phase diagram at 1261°C (1534 K) for a stainless steel, type CN-7MS, using Si alone as a melting point depressant, rather than carbon. Because stainless steels usually have low carbon concentration, it is reasonable and possible to use silicon (Si) as the MPD.
- Fig. 15, relates weight percent chromium (Cr) to weight percent silicon (Si) .
- Fig. 15 is phase diagram at 1261°C (1534 K) for a stainless steel, type CN-7MS, using Si alone as a melting point depressant, rather than carbon. Because stainless steels usually have low carbon concentration, it is reasonable and possible to use silicon (Si) as the MPD.
- Fig. 15, relates weight percent chromium (Cr) to weight percent silicon (Si) .
- the amount of Ni is
- FIG. 16 is a phase diagram showing the CN-7MS silicon system relating temperature (°C) to weight percent Si, with concentrations of: Cr 19%; Mn 1%; Ni 23.5%; Mo 2.75%; Cu 1.75%; C 0.05%; Si 0 to 8% and a balance of Fe (all wt%) .
- a target composition ' T in Fig. 16 at 3 wt% Si is shown, along with complementary skeleton composition K of Si (0.754% wt) and infiltrant composition I (6.836% wt) at 1261°C.
- Fig. 15 shows an equilibrium solid composition S of about 1.96% wt Si and 17.53% wt Cr, and an equilibrium liquid composition L of about 4.78% wt Si and 21.51% wt Cr. It also shows the same compositions for the basic style method at KA and IA for the skeleton and infiltrant, respectively, showing also the concentration of Cr at about 19%. (These are also analogous to the skeleton K and Infiltrant I above) .
- the near tie-line style composition for skeleton and infiltrant would be at KB (0.754 w% Si; 17.53 w% Cr) and IB (6.836 w% Si; 21.51 w% Cr) respectively.
- infiltrated bodies In general, conventional heat treating techniques (analytical and operational) are applicable to infiltrated bodies. Three broad categories of infiltrated bodies have been described: those with complete solubility of the MPD in the austenite, for instance austenitic-manganese steel; those with large but not complete solubility of the MPD, such as A3; and those that show limited solubility of the MPD, such as D2.
- Fig. 19 and Fig. 6 are instructive.
- the infiltrated body will transform from the two-phase body discussed, to a one phase, wholly solid FCC body, in which all of the Carbon is fully dissolved.
- the body can be quenched to form an alloy that will retain a predominantly austenite structure, with few carbides present.
- the material should not be tempered. Surface hardening may be done by grit blasting or shot peening . Homogeni zation
- the table below shows, for a 60% solid basic method A3 alloy heat treated at 1150 °C, the amounts of the phase present and carbon content.
- the skeleton has increased its carbon content from 0.37% wt to 1.12% wt .
- the carbon concentration in the infiltrant has decreased from 2.67% wt to 1.45% wt .
- there is a carbon content difference of 1.45-1.12 0.33% wt C between the formerly skeleton region and formerly infiltrant region.
- the VC is stable in the field, which is very helpful, because it helps to pin the austenite grain boundaries, and not to suffer from grain growth during heat treatment, as compared, for instance to austenitic-manganese steel.
- D2 is a suitable example, and reference should be made to Fig. 3 and Fig. 8.
- the infiltrant region has decreased its carbon content from 3.5% wt to 2.61% wt . Despite some carbon rearrangement, there is still a large difference in carbon content between the skeleton and infiltrant. This assumes that all the M 7 C 3 carbide formed at equilibrium at 1150 °C is present in the infiltrated region and none in the skeleton region, resulting in a carbide difference of 25.1 wt% between skeleton and infiltrant.
- the carbides that do not dissolve in the FCC •solid are typically the largest carbides. Further, the carbide phase tends to coarsen, if heated for long times, by a dissolution reprecipitation mechanism, also known as Oswald ripening.
- Custom D2 powder with low carbon content and a particle size ⁇ 150 ⁇ m was fabricated to perform infiltration testing. Successful infiltrations using the basic style method were possible with powder size ranging from 25 ⁇ m to 150 ⁇ m. With a starting packing fraction of -60% vol, the optimal infiltration temperature is between 1270°C and 1280°C. Lower temperatures resulted in incomplete infiltrations and higher temperatures increased the risk of erosion. This results in an equilibrium solid fraction of about 70% wt, which corresponds to ⁇ 10% solidification during infiltration. The infiltrated samples reached around 99% of the theoretical density of D2 tool steel. The cause for the slight lower density was microporosity found in cross sections .
- the infiltrated test specimens and commercial D2 tool steel were austenitized for 30 min in a temperature range between 850°C and 1150°C and quenched in air to examine the hardening behavior. Both reached as-quenched hardness of around 60 HRC. The difference was an optimal austenitizing temperature of 1030°C for the commercial D2 tool steel and 1080°C for the infiltrated samples. The reason for this is the different microstructure.
- the commercial D2 tool steel had a fine dispersion of carbide, whereas the infiltrated samples had a more or less closed carbide network on the grain boundaries. This results in a larger diffusion distance for the homogenization of carbon of the austenite during austenitizing.
- inventions disclosed and described herein include methods of infiltrating metal skeletons with an infiltrant of a similar composition, but with a melting point depressant to produce a steel product.
- inventions disclosed herein include methods of infiltrating, methods of designing an infiltration process, methods of establishing appropriate complementary pairs of skeleton and infiltrant compositions, to arrive at a bulk composition that can be infiltrated, and that is sufficiently near to a desired target.
- Additional inventions disclosed also include metal products made according to the methods of infiltration and design, and formulations for metal powders to constitute skeletons and infiltrants, either alone, or as complementary pairs. The inventors also consider to be their invention the foregoing inventions, further in combination with steps to homogenize infiltrated bodies, either at or near the infiltration temperature, or at lower temperatures, such as at an austenitizing temperature.
- the methods of designing a process can be used to develop systems having one, two or more elements as part of the melting point depressant agent, to be used for any of the modes of complementarity discussed.
- the methods of design including packing fraction driven and skeleton composition driven, include a large number of steps to arrive most precisely at a desired outcome.
- the invention also includes methods with fewer steps, some of which may become unnecessary or superfluous for an experienced operator. For instance, it may not be necessary to explicitly decide upon a temperature margin T SAFE as the operator may be able to just estimate what amount of carbon to remove from the equilibrium solid amount to achieve a skeleton that will surely not sag during infiltration at a given temperature. Further, the order that the steps are taken is not necessarily as set forth on the flow charts. Thus, it is considered an invention hereof to perform the methods of designing systems by conducting the steps in different orders, or with some of the steps removed, and, in some cases, with additional steps added.
- One invention disclosed herein is a method for fabricating a steel part having a target bulk composition T of iron (Fe) and N additional basic elements E x , E 2 , ... E N , where N ⁇ 1, each present in a respective mass percentage M l ⁇ , M 2 _ ⁇ , ... M N;T , and a melting point depressant agent E MED , present in a mass percentage M MPD _ T .
- the method comprises the steps of: providing a skeleton of interconnected adhered metal particles having a network of interconnected porosities throughout, the particles packed at a packing fraction V pp , the particles having a composition consisting essentially of: iron and the N basic elements E x , E 2 , ...
- the method further comprises providing an infiltrant having a composition consisting essentially of: iron and the same N elements E l t E 2 , ... E N , each present in a respective mass percentage M lfI , M 2/I , ... M NI ; and the Melting Point Depressant agent E MPD , present in a mass percentage M MPD;I , where M MPD/I > M MPD(T > M MPD>K .
- the infiltrant composition is complementary to the skeleton composition, relative to the bulk target composition T.
- the method also comprises infiltrating the skeleton with the infiltrant, at an infiltration temperature T infil , the infiltration being driven primarily by capillary pressure.
- the infiltration temperature, the infiltrant composition and the skeleton composition are such that: T infil is below a solidus temperature for the skeleton; T infil is above a liquidus temperature for the infiltrant; and at the infiltration temperature, T infil , at chemical equilibrium, a body having the target composition T, has at least about 7 vol% liquid, and is less than about 50 vol% liquid.
- the melting point depressant agent can be a single element agent of either Carbon or Silicon, without any other elements that have a significant melting point depressing activity, as composed in the infiltrant as compared to the skeleton.
- the melting point depressant agent can be Carbon and Silicon together, again, without any other elements that have a significant melting point depressing activity.
- either carbon or silicon or both can be used with other melting point depressants, which have a relatively high solubility and a relatively high diffusivity in the skeleton.
- relatively high it is meant generally high enough so that an infiltrated part can be homogenized to near homogeneity in a time period that is reasonable, generally less than 24 hours, and preferably less than 15 hours, 'and most preferably less than three hours, given an operator's cost structure.
- the melting point depressant agent has a maximum solubility M MPD . max in iron (Fe) , and the melting point depressant mass percentage in the target composition M MPD ⁇ T is less than about 2*M MPD _ max and more preferably, less than M MPD _ max .
- the method further comprises subjecting the infiltrated skeleton to conditions such that a portion of the melting point depressant diffuses from the infiltrated porosities into the metal powder, and at least partial diffusional solidification occurs. For instance, diffusional solidification of at least 10% or more of the volume of the infiltrated infiltrant can occur.
- Still another preferred embodiment further comprises providing an infiltrant having a composition that is complementary to the composition of the skeleton with respect to the target bulk composition, in a mode that is between a near tie-line mode and a reverse slope mode, or, between a near tie-line mode and a basic mode.
- Other preferred embodiments are characterized by providing infiltrant and skeleton pairs that are complementary in an off tie-line mode.
- Various preferred embodiments include using a target bulk composition of a steel selected from the group consisting of: D2, M2, 440C, Austenitic Manganese Grade C, A3, 06, 410 and T8. In those cases, it is a preferred embodiment to employ carbon as the principal, or only significant melting point depressant.
- Other preferred embodiments include using a target bulk composition of a steel selected from the group consisting of: CN-7MS CF-lOSMnN, in which cases it is convenient that silicon be the principal or only melting point depressant.
- a target bulk composition comprising a steel selected from the group consisting of: H13, S6 And ACI-HF, both silicon and carbon can be used as components of a melting point depressant agent.
- the melting point depressant agent is present in the skeleton in a mass percentage between zero and the mass percentage of the melting point depressant agent in an equilibrium solid phase of the target composition at a temperature where the target composition is 93 vol% solid.
- the slowest diffusing elements of the melting point depressant agent have a diffusivity in the skeleton at 1100°C of greater than 4 x 10 ⁇ l ⁇ cm/sec or, more preferably, of greater than 2 x 10 "15 can 2 /sec.
- an invention includes maintaining the skeleton after infiltration at the infiltration temperature for a period of time less than fifteen hours, and, more preferably, less than 3 hours, with the melting point depressant having a diffusivity such that substantial homogeneity is achieved.
- a related invention includes the step of maintaining the skeleton after infiltration at an austenitizing temperature for a period of time less than 3 hours, the melting point depressant having a diffusivity such that substantial homogeneity is achieved.
- Another embodiment that is preferred is a method for fabricating a steel part having a target bulk composition T as set forth in the row entitled Target range in the immediately following table: C Cr Mn Mo Ni Si V Fe
- the method of fabricating comprises the steps of: providing a skeleton of interconnected adhered metal particles having a network of interconnected porosities throughout, the particles packed at a packing fraction V PF .
- the particles have a composition consisting essentially of: iron and the additional basic elements each present in a respective mass percentage between those as specified in a column headed by the respective element symbol in: the row entitled Skeleton-B; and the row entitled Skeleton-D; and Carbon, present in a mass percentage between zero and the mass percentage of carbon in an equilibrium solid phase of the target composition at a temperature where the target composition T is 93 vol% solid.
- the method further comprises providing an infiltrant having a composition consisting essentially of: iron and the same additional basic elements each present in a respective mass percentage between approximately what is specified in a column headed by the respective element symbol in: a row entitled Infiltrant-B; and a row entitled Infiltrant-D; and Carbon, present in a mass percentage of at least the mass percentage of carbon in the equilibrium liquid phase of the target composition, at a temperature where the target composition is 50 vol% liquid.
- the infiltrant composition and the skeleton composition further are complementary relative to the target composition T.
- the method also includes infiltrating the skeleton with the infiltrant, at the infiltration temperature T infil , the infiltration being driven primarily by capillary pressure, the infiltration temperature, the infiltrant composition and the skeleton composition further being such that: T infil is below a solidus temperature for the skeleton; T infil is above a liquidus temperature for the infiltrant; and at the infiltration temperature, T infil , at chemical equilibrium, a body having the target composition T, has at least about 7% vol liquid, and is less than about 50% vol liquid.
- Such a method would include essentially any combination of infiltrant and skeleton discussed above for the D2 steel system, for packing fractions between 50 vol% and 70 vol%, for all modes between reverse slope and near tie line.
- a further preferred embodiment is a method similar to that just mentioned, but where the infiltrant and skeleton compositions are in a complementary mode between that of a near tie-line and a basic mode.
- the step of providing a skeleton further comprises providing a skeleton of particles having a composition consisting essentially of: iron and the additional basic elements, each present in a respective mass percentage between approximately as specified in the column headed by the respective element symbol in: a row entitled Skeleton-A of the immediately following table: Cr Mn Mo Ni Si V Fe
- the step of providing an infiltrant further comprises providing an infiltrant having a composition consisting essentially of: iron and the same additional basic elements each present in a respective mass percentage between approximately as specified in the column headed by the respective element symbol in: the row entitled Infiltrant-A; and the row entitled Infiltrant-B; and Carbon, present in the same infiltrant mass percentage just specified.
- Still another preferred embodiment is similar to the last two, but is for CN-7MS Steel, but with silicon being the principal MPD, rather than carbon, where the corresponding table for the Infiltrant-D and Skeleton-D values, and the Infiltrant-B and Skeleton-B values is: C Cr Mn Mo Ni Si Cu Fe
- Yet another preferred embodiment is similar to the preceding four, but is for H13 Steel, with silicon and carbon being the principal elements of the MPD agent, rather than carbon or silicon alone.
- the corresponding table for the Infiltrant-D and Skeleton-D values, and the Infiltrant-B and Skeleton-B values is :
- Yet another preferred embodiment is a method for designing a process for fabricating a steel part by infiltrating a skeleton of metal particles.
- the process further entails determining a temperature, T PF , at which the composition T has a solid portion V s equal in volume to V ⁇ and a liquid portion V L equal in volume to V v .
- a tie line composition at T PF is determined for the solid and liquid portions, comprising mass percentages of each of the elements of the target composition T, the mass percentages designated: for the solid M l ⁇ S , M 2rS , ... M N;S respectively, and the MPD agent M MPD _ S ; and for the liquid M ljL , M 2/L , ... M N/L respectively, and the MPD agent M MPD;L .
- a skeleton and an infiltrant composition for the basic elements is determined, each comprising mass percentages of iron and each of the basic elements of the target composition T, the mass percentages designated, for the skeleton M l ⁇ K , M 2 ⁇ K , ... M N/K respectively and for the infiltrant designated M l ⁇ I t M 2 ⁇ I , ... M N;I respectively.
- a temperature range T SAFE is selected, and a skeleton solidus temperature, T ⁇ s , equal to T PF +T SAFE is also determined.
- a related preferred embodiment further entails the steps of: determining a liquidus temperature T IL , for the infiltrant composition of the basic elements in mass percentages' M 1#I , M 2/I , ... M N ⁇ I , and the MPD element in mass percentage M MPDI ; and comparing the infiltrant liquidus temperature T IL to the proposed infiltration temperature T infil .
- T IL ⁇ T infil the skeleton can be infiltrated with the infiltrant composition at the proposed infiltration temperature T inf . If T IL ⁇ T infil , then it is useful to reevaluate at least one of the parameters PF, T SAFE , or ⁇ V and return to the step of selecting a particle type.
- the step of determining a skeleton composition for the basic elements comprises assigning the mass percentages designated M ⁇ , ⁇ ' M 2 , ⁇ ' - M N , K equal to the corresponding mass percentages of the basic elements in the target composition, M l ⁇ T , M 2 _ ⁇ , ... M N _ T respectively.
- the step of determining a skeleton composition for the basic elements comprises assigning the mass percentages equal to the corresponding mass percentages of the basic elements in the tie line solid portion composition, M l ⁇ S , M 2 _ s , ...
- a preferred method includes the step of determining a skeleton composition, comprising, for the basic elements, designating a respective factor R 1; R 2 ,... R N , where each R,. factor 0 ⁇ R_ ⁇ 1, and where at least one R ⁇ factor 0 ⁇ R n ⁇ l.
- a preferred method includes steps that are identical to that immediately mentioned, except that each R ⁇ factor -l ⁇ R n ⁇ O, and where at least one R-. factor R,. ⁇ 0.
Abstract
Description
Claims
Priority Applications (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
CA002546485A CA2546485A1 (en) | 2003-11-26 | 2004-11-22 | Infiltrating a powder metal skeleton by a similar alloy with depressed melting point exploiting a persistent liquid phase at equilibrium, suitable for fabricating steel parts |
EP04811793A EP1694457A2 (en) | 2003-11-26 | 2004-11-22 | Infiltrating a powder metal skeleton by a similar alloy with depressed melting point exploiting a persistent liquid phase at equilibrium, suitable for fabricating steel parts |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US10/723,989 US7250134B2 (en) | 2003-11-26 | 2003-11-26 | Infiltrating a powder metal skeleton by a similar alloy with depressed melting point exploiting a persistent liquid phase at equilibrium, suitable for fabricating steel parts |
US10/723,989 | 2003-11-26 |
Publications (2)
Publication Number | Publication Date |
---|---|
WO2005053883A2 true WO2005053883A2 (en) | 2005-06-16 |
WO2005053883A3 WO2005053883A3 (en) | 2005-08-04 |
Family
ID=34592449
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/US2004/039133 WO2005053883A2 (en) | 2003-11-26 | 2004-11-22 | Infiltrating a powder metal skeleton by a similar alloy with depressed melting point exploiting a persistent liquid phase at equilibrium, suitable for fabricating steel parts |
Country Status (4)
Country | Link |
---|---|
US (1) | US7250134B2 (en) |
EP (1) | EP1694457A2 (en) |
CA (1) | CA2546485A1 (en) |
WO (1) | WO2005053883A2 (en) |
Families Citing this family (27)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20060065327A1 (en) * | 2003-02-07 | 2006-03-30 | Advance Steel Technology | Fine-grained martensitic stainless steel and method thereof |
WO2005056855A1 (en) * | 2003-12-03 | 2005-06-23 | Hoeganaes Corporation | Methods of preparing high density powder metallurgy parts by iron based infiltration |
AU2012362827B2 (en) | 2011-12-30 | 2016-12-22 | Scoperta, Inc. | Coating compositions |
US20150275341A1 (en) | 2012-10-11 | 2015-10-01 | Scoperta, Inc. | Non-magnetic metal alloy compositions and applications |
EP3033188A4 (en) | 2013-08-16 | 2017-03-22 | The Exone Company | Three-dimensional printed metal-casting molds and methods for making the same |
WO2015057761A1 (en) | 2013-10-17 | 2015-04-23 | The Exone Company | Three-dimensional printed hot isostatic pressing containers and processes for making same |
CA2931842A1 (en) | 2013-11-26 | 2015-06-04 | Scoperta, Inc. | Corrosion resistant hardfacing alloy |
WO2015100086A1 (en) | 2013-12-23 | 2015-07-02 | The Exone Company | Methods and systems for three-dimensional printing utilizing multiple binder fluids |
US11001048B2 (en) | 2013-12-23 | 2021-05-11 | The Exone Company | Method of three-dimensional printing using a multi-component build powder |
EP3148730A1 (en) | 2014-05-29 | 2017-04-05 | The Exone Company | Process for making nickel-based superalloy articles by three-dimensional printing |
CN106661702B (en) | 2014-06-09 | 2019-06-04 | 斯克皮尔塔公司 | Cracking resistance hard-facing alloys |
US20170203514A1 (en) | 2014-07-17 | 2017-07-20 | The Exone Company | Methods and Apparatuses for Curing Three-Dimensional Printed Articles |
WO2016014851A1 (en) * | 2014-07-24 | 2016-01-28 | Scoperta, Inc. | Hardfacing alloys resistant to hot tearing and cracking |
US10465269B2 (en) | 2014-07-24 | 2019-11-05 | Scoperta, Inc. | Impact resistant hardfacing and alloys and methods for making the same |
JP6764401B2 (en) * | 2014-10-15 | 2020-09-30 | ザ エクスワン カンパニー | Method of suppressing deformation of cavities during heat treatment of three-dimensional printed matter |
WO2016089618A1 (en) | 2014-12-03 | 2016-06-09 | The Exone Company | Process for making densified carbon articles by three dimensional printing |
EP3234209A4 (en) | 2014-12-16 | 2018-07-18 | Scoperta, Inc. | Tough and wear resistant ferrous alloys containing multiple hardphases |
EP3253516B1 (en) | 2015-02-03 | 2021-09-22 | The Nanosteel Company, Inc. | Infiltrated ferrous materials |
CA2997367C (en) | 2015-09-04 | 2023-10-03 | Scoperta, Inc. | Chromium free and low-chromium wear resistant alloys |
AU2016321163B2 (en) | 2015-09-08 | 2022-03-10 | Scoperta, Inc. | Non-magnetic, strong carbide forming alloys for powder manufacture |
EP3374536A4 (en) | 2015-11-10 | 2019-03-20 | Scoperta, Inc. | Oxidation controlled twin wire arc spray materials |
PL3433393T3 (en) | 2016-03-22 | 2022-01-24 | Oerlikon Metco (Us) Inc. | Fully readable thermal spray coating |
CN109641273A (en) | 2016-09-21 | 2019-04-16 | S·辛戈夫 | 3D printer |
US20180305266A1 (en) * | 2017-04-24 | 2018-10-25 | Desktop Metal, Inc. | Additive fabrication with infiltratable structures |
JP2022505878A (en) | 2018-10-26 | 2022-01-14 | エリコン メテコ(ユーエス)インコーポレイテッド | Corrosion-resistant and wear-resistant nickel-based alloy |
CN111363941B (en) * | 2020-03-27 | 2021-06-29 | 陕西理工大学 | Polygonal microstructure tungsten alloy material and preparation method and application thereof |
US20230313345A1 (en) * | 2022-03-30 | 2023-10-05 | Relativity Space, Inc. | Aluminum Alloy Compositions, Articles Therefrom, and Methods of Producing Articles Therefrom |
Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4286987A (en) * | 1979-11-28 | 1981-09-01 | United States Bronze Powders, Inc. | Composition for iron powder compact infiltrant |
US4327156A (en) * | 1980-05-12 | 1982-04-27 | Minnesota Mining And Manufacturing Company | Infiltrated powdered metal composite article |
Family Cites Families (15)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3652261A (en) | 1969-06-25 | 1972-03-28 | American Metal Climax Inc | Iron powder infiltrant |
US4455354A (en) | 1980-11-14 | 1984-06-19 | Minnesota Mining And Manufacturing Company | Dimensionally-controlled cobalt-containing precision molded metal article |
US4478638A (en) | 1982-05-28 | 1984-10-23 | General Electric Company | Homogenous alloy powder |
US4710273A (en) | 1985-08-08 | 1987-12-01 | Ethyl Corporation | Olefin purification process |
GB2197663B (en) | 1986-11-21 | 1990-07-11 | Manganese Bronze Ltd | High density sintered ferrous alloys |
US4971755A (en) | 1989-03-20 | 1990-11-20 | Kawasaki Steel Corporation | Method for preparing powder metallurgical sintered product |
US5236032A (en) | 1989-07-10 | 1993-08-17 | Toyota Jidosha Kabushiki Kaisha | Method of manufacture of metal composite material including intermetallic compounds with no micropores |
US5204055A (en) | 1989-12-08 | 1993-04-20 | Massachusetts Institute Of Technology | Three-dimensional printing techniques |
US5848349A (en) | 1993-06-25 | 1998-12-08 | Lanxide Technology Company, Lp | Method of modifying the properties of a metal matrix composite body |
US5509555A (en) | 1994-06-03 | 1996-04-23 | Massachusetts Institute Of Technology | Method for producing an article by pressureless reactive infiltration |
US5745834A (en) | 1995-09-19 | 1998-04-28 | Rockwell International Corporation | Free form fabrication of metallic components |
US5791397A (en) | 1995-09-22 | 1998-08-11 | Suzuki Motor Corporation | Processes for producing Mg-based composite materials |
DE69827844T2 (en) | 1997-09-26 | 2005-12-08 | Massachusetts Institute Of Technology, Cambridge | METHOD FOR PRODUCING PARTS FROM POWDER USING BINDER PRODUCED FROM METAL SALT |
US6719948B2 (en) | 2000-05-22 | 2004-04-13 | Massachusetts Institute Of Technology | Techniques for infiltration of a powder metal skeleton by a similar alloy with melting point depressed |
JP2003534454A (en) * | 2000-05-22 | 2003-11-18 | マサチューセッツ インスティテュート オブ テクノロジー | Infiltration method of powder metal skeleton of similar substance using melting point depressant |
-
2003
- 2003-11-26 US US10/723,989 patent/US7250134B2/en active Active
-
2004
- 2004-11-22 EP EP04811793A patent/EP1694457A2/en not_active Withdrawn
- 2004-11-22 WO PCT/US2004/039133 patent/WO2005053883A2/en active Application Filing
- 2004-11-22 CA CA002546485A patent/CA2546485A1/en not_active Abandoned
Patent Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4286987A (en) * | 1979-11-28 | 1981-09-01 | United States Bronze Powders, Inc. | Composition for iron powder compact infiltrant |
US4327156A (en) * | 1980-05-12 | 1982-04-27 | Minnesota Mining And Manufacturing Company | Infiltrated powdered metal composite article |
Also Published As
Publication number | Publication date |
---|---|
US7250134B2 (en) | 2007-07-31 |
WO2005053883A3 (en) | 2005-08-04 |
US20050109431A1 (en) | 2005-05-26 |
EP1694457A2 (en) | 2006-08-30 |
CA2546485A1 (en) | 2005-06-16 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
US7250134B2 (en) | Infiltrating a powder metal skeleton by a similar alloy with depressed melting point exploiting a persistent liquid phase at equilibrium, suitable for fabricating steel parts | |
Fayazfar et al. | A critical review of powder-based additive manufacturing of ferrous alloys: Process parameters, microstructure and mechanical properties | |
Karthik et al. | Heterogeneous aspects of additive manufactured metallic parts: a review | |
DE102016202885B4 (en) | Selective laser sintering process | |
US6814926B2 (en) | Metal powder composition for laser sintering | |
KR20180109891A (en) | High durability, high performance steel for structural, machine and tool applications | |
EP3352985A1 (en) | Infiltrated segregated ferrous materials | |
US20220049331A1 (en) | Long durability high performance steel for structural, machine and tooling applications | |
Großwendt et al. | Additive manufacturing of a carbon-martensitic hot-work tool steel using a powder mixture–Microstructure, post-processing, mechanical properties | |
Andreiev et al. | Laser beam melting of functionally graded materials with application-adapted tailoring of magnetic and mechanical performance | |
EP0246233A1 (en) | Tool steel. | |
Tian et al. | Laser powder bed fusion of M789 maraging steel on Cr–Mo N709 steel: Microstructure, texture, and mechanical properties | |
JP5896296B2 (en) | Manufacturing method of high-strength mold with excellent high-temperature softening resistance | |
Kernan et al. | Homogeneous steel infiltration | |
Simchi et al. | Microstructural development during additive manufacturing of biomedical grade Ti-6Al-4V alloy by three-dimensional binder jetting: Material aspects and mechanical properties | |
Vallabhajosyula et al. | Modeling and production of fully ferrous components by indirect selective laser sintering | |
Steinlechner | Development of Laser Powder Bed Fusion parameters and their effect on microstructure formation in Low Alloyed Steels | |
He et al. | A review on the science of plastic deformation in laser-based additively manufactured steel | |
CN1847437A (en) | High-strength damping alloys and low-noise diamond saw using the same | |
Kearns et al. | STUDIES ON THE EFFECTS OF NIOBIUM ON SINTERING AND PROPERTIES OF MIM 440C MADE BY PREALLOY AND MASTER-ALLOY ROUTES. | |
Pelz et al. | Functionally graded cast tools for hot forging applications | |
Hill | Microstructure and mechanical properties of titanium alloys reinforced with titanium boride | |
Aljamal | Process Optimization of Additive Manufacturing of Tool Steels | |
Kariyawasam | Advances in Sintering of Powder Metallurgy Steels | |
Ley | Binder Jet Printing of a Low-Cost Tool Steel Powder |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
AK | Designated states |
Kind code of ref document: A2 Designated state(s): AE AG AL AM AT AU AZ BA BB BG BR BW BY BZ CA CH CN CO CR CU CZ DE DK DM DZ EC EE EG ES FI GB GD GE GH GM HR HU ID IL IN IS JP KE KG KP KR KZ LC LK LR LS LT LU LV MA MD MG MK MN MW MX MZ NA NI NO NZ OM PG PH PL PT RO RU SC SD SE SG SK SL SY TJ TM TN TR TT TZ UA UG US UZ VC VN YU ZA ZM ZW |
|
AL | Designated countries for regional patents |
Kind code of ref document: A2 Designated state(s): GM KE LS MW MZ NA SD SL SZ TZ UG ZM ZW AM AZ BY KG KZ MD RU TJ TM AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HU IE IS IT LU MC NL PL PT RO SE SI SK TR BF BJ CF CG CI CM GA GN GQ GW ML MR NE SN TD TG |
|
121 | Ep: the epo has been informed by wipo that ep was designated in this application | ||
WWE | Wipo information: entry into national phase |
Ref document number: 2546485 Country of ref document: CA |
|
NENP | Non-entry into the national phase |
Ref country code: DE |
|
WWW | Wipo information: withdrawn in national office |
Country of ref document: DE |
|
WWE | Wipo information: entry into national phase |
Ref document number: 2004811793 Country of ref document: EP |
|
WWP | Wipo information: published in national office |
Ref document number: 2004811793 Country of ref document: EP |