WO2013049652A1

WO2013049652A1 - Bonded abrasives formed by uniaxial hot pressing

Info

Publication number: WO2013049652A1
Application number: PCT/US2012/058033
Authority: WO
Inventors: Marc Linh HOANG
Original assignee: Saint-Gobain Abrasives, Inc.; Saint-Gobain Abrasifs
Priority date: 2011-09-29
Filing date: 2012-09-28
Publication date: 2013-04-04
Also published as: WO2013049652A4; JP2014526397A; EP2760637A4; KR20140075719A; RU2014114620A; EP2760637A1; BR112014007136A2; CN103826801A; US20130081334A1

Abstract

A particular method includes uniaxially hot pressing a preform that includes abrasive particles in a bonding material to form a bonded abrasive body.

Description

BONDED ABRASIVES FORMED BY UNIAXIAL HOT PRESSING

TECHNICAL FIELD

The present disclosure generally relates to bonded abrasives, and more particularly to forming bonded abrasive articles through uniaxial hot pressing. BACKGROUND ART

Uniaxial pressing has typically been restricted to bodies having uniform cross- sections, as non-uniform cross-sections may react unpredictably to the application of pressure. Pressure applied to a body having a non-uniform cross-section may result in a distortion of shape and/or non-uniform density. Uniaxial hot pressing has also typically been restricted to bodies having uniform compositions, in order to avoid differing amounts of shrinkage resulting from variable coefficients of thermal expansion. Differing amounts of shrinkage can result in regions of partially undensified material or regions of increased stress.

US patent number 4,153,666 discloses hot pressing a preformed shape which deforms orderly to a final shape in a mold against preformed parts having surfaces exactly mating with the surfaces of the preform. The preformed parts are formed of a powdered composition having the same compaction ratio as the preform and a coefficient of thermal expansion substantially equal to that of the preform.

US patent numbers 6,306,325 and 6,508,964 disclose hot pressing ceramic bodies in a mold, wherein the ceramic bodies are homogeneous in composition.

US patent number 3,467,745 discloses hot pressing refractory carbide bodies with shaped cavities by incorporating a water-reactive carbide in amounts and at locations corresponding to the locations and size of the cavities desired in the final body. The water-reactive carbide may be leached out with water following pressing. US patent number 5,250,130 discloses hot pressing a green body with a nonuniform compositional cross-section relative to the axial direction by laminating auxiliary material with the green body in the axial direction to achieve a uniform shrinkage that is substantially equal across the laminate. The auxiliary material is delaminated from the body after hot pressing.

SUMMARY OF THE INVENTION In a particular embodiment, a method includes uniaxially hot pressing a preform that includes abrasive particles in a bonding material to form a bonded abrasive body.

In another embodiment, a method includes uniaxially hot pressing a preform that includes abrasive particles to form a body having a relief extending from a plane on the body that is parallel to an axis of pressing.

In another embodiment, a method of forming a bonded abrasive body includes forming a green body comprising abrasive particles and a bonding material. The method further includes placing the green body in a mold and uniaxially hot pressing the green body to form the bonded abrasive body. In another embodiment, a method includes forming a mixture of abrasive particles and bonding material, forming the mixture into a green body, and placing the green body in a mold. The method further includes uniaxially hot pressing the mold to form a bonded abrasive body with a near net shape that is asymmetric around a pressing axis. In another embodiment, a method includes uniaxially hot pressing a green body preform to form a composite body. Pressing includes liquid phase sintering, and during pressing the geometry of the preform is substantially altered.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure may be better understood, and its numerous objects, features, and advantages made apparent to those skilled in the art by referencing the accompanying drawings. FIG. 1 includes a flow diagram illustrating a particular embodiment of a method of making an abrasive tool having a relief.

FIG. 2a includes an illustration of a preform in accordance with an embodiment disclosed herein. FIG. 2b includes a top view illustration of the exemplary preform of FIG. 2a.

FIG. 3a includes an illustration of a particular embodiment of a single mold for making an abrasive tool.

FIG. 3b includes an illustration of a particular embodiment of a mold for use in a mold pack for making an abrasive tool. FIG. 4 includes an illustration of a particular embodiment of a loaded mold before pressing.

FIG. 5 includes an illustration of a particular embodiment of a loaded mold pack before pressing.

FIG. 6 includes a cross-sectional view to illustrate a particular embodiment of a pressing operation.

FIG. 7 includes an illustration of a particular embodiment of a mold after pressing.

FIG. 8 includes an illustration of a particular embodiment of a mold pack after pressing. FIG. 9a includes an illustration of a particular embodiment of an abrasive tool with a relief.

FIG. 9b includes an illustration of a plane of the exemplary abrasive tool of FIG. 9a.

Fig. 9c includes a side-view illustration of the exemplary abrasive tool of FIGs. 9a and 9b. FIGs. 10a, 10b, and 10c include illustrations of multiple exemplary embodiments of abrasive tools with alternative relief orientations.

The use of the same reference symbols in different drawings indicates similar or identical items. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

According to one aspect of the present disclosure, a method is disclosed that includes uniaxially hot pressing a preform that includes abrasive particles in a bonding material to form a bonded abrasive body. With uniaxial hot pressing, a force is applied to a body in substantially one direction or along a single axis while heat is applied to the body such that the geometric shape of the body is substantially changed. The axis along which force is applied during uniaxial hot pressing is referred to herein as the axis of pressing. Thus, according to one aspect of the present disclosure, a bonded abrasive body may be formed by hot pressing a preform (e.g., a green or unsintered body) along a single axis (i.e., the axis of pressing). FIG. 1 includes a method 100 of making an abrasive tool using a uniaxial hot pressing process according to an embodiment. The method 100 includes combining abrasive particles with a bonding material to form a mixture, at step 102. The abrasive particles can include inorganic materials, such as oxides, carbides, nitrides, borides, oxynitrides, oxycarbides, or a combination thereof. In one particular instance, abrasive particles can include alumina, silica carbide, silica, ceria, or a combination thereof. Particular embodiments may utilize abrasive particles made of superabrasive material. Suitable superabrasives may include diamond, cubic boron nitride (CBN), or a combination thereof. In one particular embodiment, the abrasive particles can consist essentially of diamond. Further, in another particular embodiment, the abrasive particles can include diamond grit present in an amount of 3.5% vol% or less.

The bonding material can include an inorganic material. In an embodiment, the major content (e.g., greater than 50% by volume, weight, or molar percentage) of the bonding material may include an inorganic material. For example, the bonding material may be a ceramic, such as a vitreous material. In another example, the bonding material may include a metal or a metal alloy. For example, the bonding material can include one or more transition metal elements. Suitable transition metal elements can include, but are not limited to, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, tin, zirconium, silver, molybdenum, tantalum, tungsten, or a combination thereof. Specifically, the bonding material can include one or more transition metal elements selected from the group including cobalt, iron, copper, and nickel. In a particular aspect, the bonding material can include an electrolytic iron powder, pre-alloyed bronze, a nickel base alloy, or a combination thereof. In an exemplary, non-limiting embodiment, the bonding material can include 40 wt% electrolytic iron powder (-315 mesh), 48 wt% water atomized pre-alloyed bronze 90/10 (-200 mesh), and 12 wt% nickel base alloy (53- 75 μιη).

In another example, the bonding material can include an organic material. In an embodiment, the major content (e.g., greater than about 50% by volume, weight, or molar percentage) of the bonding material may include an organic material.

Illustrative organic materials can include polymers such as glycol, resin, dextrin, glue, polyethylene, ethylene, propylene, polyvinyl alcohol, or a combination thereof. In a particular instance, the bonding material may be a resin. Illustrative resins may include thermosets, thermoplastics, or a combination thereof. For example, resins can include phenolics, such as novolak and resole, epoxies, polyesters, such as unsaturated polyesters, cyanate esters, shellacs, polyurethanes, rubber, polyimides, bismaleimides, melamines, or a combination thereof.

Other embodiments may use a bonding material made of a composite material, including for example, a combination of organic and inorganic materials. For example, the bonding material can include a combination of a metal material combined with a polymer material (e.g., a resin).

In addition to the abrasive particles and bonding materials, the mixture may contain other materials, such as additives. It will be appreciated that additives may be included within the mixture to facilitate proper formation of the final abrasive body. Examples of such additives can include stabilizers, binders, surfactants, pore formers, and the like. The additives can also include lubricants, such as a graphite powder lubricant additive (50-150 mesh). In a particular aspect, such lubricant additives can be present in an amount less than or equal to 5.0 vol%.

Following formation of the mixture including abrasive particles and a binding material, the mixture can be formed into a preform, at step 104. For example, FIGs. 2a and 2b depict an exemplary embodiment of a preform 200. After formation of the preform, the preform may be placed in a mold, at 106. The mold may include an opening, shaped to hold a preform, and one or more recesses positioned adjacent to the opening. As an illustrative example, FIG. 3 a depicts an embodiment of a mold 300 to hold a single preform (e.g., the preform 200 of FIG. 2), and FIG. 4 depicts an exemplary embodiment of a loaded mold before pressing (e.g., the mold 300 of FIG. 3a loaded with the preform 200 of FIG. 2).

After the preform has been placed in the mold, the process can continue, at step 108, by uniaxially hot pressing the preform within the mold (e.g., the loaded mold of FIG. 4) to form a finally-formed abrasive body. In particular processes according to embodiments herein, during uniaxial hot pressing, the geometry of the preform can be substantially altered, such that the geometry of the preform is measurably altered and forms a finally-formed abrasive body having a geometry significantly different than the shape of the preform. In one embodiment, the geometry of the preform can be altered during uniaxial hot pressing to form a finally- formed abrasive body having a relief. As described in accordance with embodiments herein, the shape of the relief may depend on the shape of the mold used to hold the preform.

As described herein, FIG. 1 illustrates a particular embodiment of a method of forming a bonded abrasive body having a relief by hot pressing a preform (e.g., a green or unsintered body) along a single axis (i.e., the axis of pressing). The abrasive particles and the bonding material of a particular preform may be selected based on the type of abrasive tool to be formed.

FIGs. 2a and 2b depict an exemplary embodiment of a preform 200. As illustrated in FIGs. 2a and 2b, the preform 200 can have a body defined by a top surface 202 and a bottom surface 204 opposite the top surface 202. As illustrated, in particular instances, the top surface 202 and the bottom surface 204 may have curved contours, and particularly, may define convex and concave surfaces, respectively. The body of the preform 200 can also be defined by a front surface 225 and a rear surface 226, which are substantially planar surfaces that are substantially parallel to each other. The body of the preform 200 can also include a side surface 227 extending at an angle to the front surface 225 and the rear surface 226, which may be a substantially orthogonal angle, and join the front surface 225 and the rear surface 226. The body of the preform 200 can also include a side surface 228, spaced apart from the side surface 227 by a width (W) of the body defined along a horizontal axis 208. The side surface 228 can extend at an angle to the front surface 225 and the rear surface 226, which may be a substantially orthogonal angle, and join the front surface 225 and the rear surface 226.

In another aspect, one or more of the preform surfaces 202, 204 may not be contoured, but may be flat and extend along and define a single plate. These surfaces 202, 204 may become contoured during the forming process and may remain contoured after the forming process.

As further illustrated in FIG. 2a, the body of the preform 200 can have a length (L) defined as the longest dimension along a longitudinal axis 206, a width (W) defined as a dimension orthogonal to the length (L) along the horizontal axis 208, and a thickness (T) defined as the dimension along the side surfaces 227 and 228 perpendicular to a plane defined by the front surface 225 and the rear surface 226. The preform 200 may have a cross-sectional shape which is symmetrical about the longitudinal axis 206, as viewed in a plane defined by the length (L) and the thickness (T). Additionally, as illustrated in FIG. 2b, the preform 200 can have a cross- sectional shape that is symmetrical about a horizontal axis 208 as viewed in a plane defined by the width (W) and the thickness (T). In the particular embodiment illustrated in FIGs. 2a and 2b, the thickness (t) of the preform 200 can be uniform.

In one embodiment, the preform 200 may be a green body. It will be appreciated that a green body can be an unfinished article, for example, an unsintered material. It will be further appreciated that a green body can be a body which is not fully densified, which may undergo further processing to affect grain growth and densification. The preform 200 may be formed by a variety of forming methods, including pressing, such as hot pressing or cold pressing, molding, casting, extruding, or a combination thereof. According to one particular process, the green body can be formed by cold pressing.

In particular instances, the forming process can include the formation of a green body that has a general shape which lacks at least one design feature of the finally- formed abrasive body formed through uniaxial hot pressing. Exemplary design features can include protrusions, recesses, patterned features, and the like.

The preform 200 can include a particular content of porosity within the green body, a particular content of abrasive particles within the green body, and a particular content of bonding material within the green body. Further, the content of porosity within the green body, the content of abrasive particles within the green body, and the content of bonding material within the green body can depend on a variety of factors. These factors can include, but are not limited to, the size of the preform 200, the percentage of compaction to be applied on the preform 200 during processing (i.e., the intended amount of volume shrinkage), the compactability of the bonding material within the green body, the compactability of the abrasive particles, and the compactability of any fillers or additives, etc.

Depending upon certain processing parameters, the properties of the preform 200 can change during the forming process. For example, the size of at least a portion of the pores can be reduced during the forming process. Moreover, at least a portion of the pores can be collapsed and eliminated during the forming process. As such, the porosity of the preform 200 can be reduced during the forming process, and the porosity of the abrasive tool formed from the preform can be less than the porosity of the preform 200 before the forming process. The concentration of abrasive particles can also change due to a change in the volume of the preform 200 during the forming process to form the abrasive tool. For example, as the volume of the preform 200 is reduced during formation, the concentration of abrasive particles can increase when expressed as a percentage of total volume. The forming process can be controlled to precise condition, such that the final content of the phases (e.g., bond material, abrasive particles, fillers, and even porosity) can be precisely controlled. FIG. 3a depicts an exemplary embodiment of a mold 300 that is shaped to hold a single preform (e.g., the preform 200 of FIG. 2). According to an embodiment, the mold 300 may include carbon, and may be made of carbon, such that the mold 300 can be a carbon-based composition. It will be appreciated that "carbon-based" refers to compositions including at least 50% carbon. In another example, the mold 300 can be substantially carbon. Further, such mold consists essentially of carbon. For example, the mold 300 can be graphite.

In the embodiment illustrated in FIG. 3a, the mold 300 can include an upper portion 308 and a lower portion 309 separate from the upper portion 308 and defining an opening 302 there between. The opening 302 can be shaped to receive the preform 200. In particular, the upper portion 308 can have a surface 318 defining an upper boundary of the opening 302 and configured to directly contact a surface (e.g., lower surface 204) of the preform 200 during pressing. In particular, the surface 318 of the upper portion 306 can have a complementary curvature to the curvature of the lower surface 204 of the preform 200 for full contact during pressing. The lower portion 309 can have a surface 319 defining a lower boundary of the opening 302 and configured to directly contact a surface (e.g., upper surface 202) of the preform 200 during pressing. In particular, the surface 319 of the lower portion can have a complementary curvature to the curvature of the upper surface 202 of the preform 200 for full contact during pressing.

As further illustrated, the mold 300 can include a rear portion 310. The rear portion can be configured to engage a portion of the preform 200 during pressing, and in particular, may engage the preform 200 along a portion of the rear surface 226 during pressing. According to one embodiment, the rear portion 310 of the mold 300 can include a recess 304. The recess 304 can be an opening extending into the volume of the rear portion 310. The recess 304 can be positioned adjacent to the opening 302 and be in fluid communication with the opening 302. The recess 304 may have a shape that corresponds to a design feature of the finally-formed abrasive body (e.g., a relief or a relief pattern). In one exemplary embodiment, the recess 304 can include a surface 314 defining a bottom surface of the recess 304 that is spaced apart from the front surface 312 of the rear portion 310. The surface 314 may have a particular contour, such as a smooth contour, or alternatively, a rough surface defined by patterned features or protrusions.

In particular instances, the recess 304 can extend along the full width of the rear portion 310 between side surfaces 333 and 334, such that the recess 304 intersects with the side surfaces 333 and 334. However, in other embodiments, the recess 304 may extend for a fraction of the full width of the rear portion 310.

According to one particular embodiment, the recess 304 can have a particular contour. For example, the contour of the recess 304 can be similar to the contour of the surfaces 318 or 319 of the mold 300. In particular, the recess 304 may have a curvilinear contour, defining a convex or concave arc.

FIG. 3b includes an illustration of an alternative embodiment. In particular, FIG. 3b illustrates a mold portion, and more particularly, an alternative design for a rear portion 310. The rear portion 310 of FIG. 3b can be made of an upper portion 328 and a lower portion 329, wherein an opening is defined between the upper portion 328 and the lower portion 329. The upper portion 329 can have a recess 324, which can have the same characteristics of the recess 304 described in embodiments herein. The opening 322 can be shaped to receive a preform (e.g., preform 200). According to one embodiment, the upper portion 328 and the lower portion 329 can have the same attributes as the upper and lower portions 308 and 309 as described in accordance with embodiments herein. Partitioning of the rear portion 310 into upper and lower portions 328 and 329 can facilitate processing of multiple preforms in a mold pack, which will be described in more detail herein.

FIG. 4 includes an illustration of a loaded mold according to an embodiment. In particular, the mold has been loaded with a preform 200 between the upper portion 308 and lower portion 309. As illustrated in FIG. 4, the lower surface 204 of the preform 200 can be in direct contact with the surface 318 of the upper portion 308 of the mold 300, and the lower surface 202 of the preform 200 can be in direct contact with the surface 319 of the lower portion 309 of the mold 300. More particularly, the lower surface 204 of the preform 200 can directly contact the surface 318 of the upper portion 308 along the full width of the preform 200. Additionally, the surface 202 of the preform 200 can directly contact the surface 319 of the lower portion 309 along the full width of the preform 200. It will be appreciated that directly contacting the mold 300 refers to instances where there are no intervening layers between the preform 200 and the mold portions 308 and 309.

Furthermore, the rear surface 226 of the preform 200 can be in direct contact with a surface 312 of the rear portion 310 of the mold 300. Notably, however, a portion of the rear surface 226 can be spaced apart from the rear portion 310 at the recess 304, wherein the recess 304 includes a surface 314 defining the bottom of the recess 304, and the surface 314 can be spaced apart from the rear surface 226 of the preform 200. The space between the surface 314 and the rear surface 226 may be filled with material of the preform 200 during the pressing process.

FIG. 5 includes an illustration of a mold pack according to an embodiment. The mold pack 500 facilitates processing and shaping of multiple preforms 531 and 532 in a single uniaxial pressing operation. For example, the mold pack 500 can include a first mold portion 510 having an upper portion 511 and a lower portion 512 corresponding to the upper and lower portions 308 and 309 of the mold 300. A first preform 531 can be positioned between the upper and lower portions 511 and 512. However, the lower portion 512 can include a recess 513 formed in its rear surface 515, wherein the recess 513 extends into the volume of the lower portion 512. The recess 513 can have any features of recesses described in embodiments herein. The mold pack 500 can include a second mold portion 520 including an upper portion 521 and a lower portion 522. The upper and lower portions 521 and 522 can have the features of mold portions described in the embodiments herein. In particular, the upper portion 521 can have a recess 523 formed in its front surface 525, wherein the recess 523 extends into the volume of the upper portion 521. In particular, the mold pack 500 can utilize the first and second mold portions

510 and 520, which are oriented with respect to each other to facilitate processing of multiple preforms in a single pressing operation. Notably, during pressing, the first and second mold portions 510 and 520 can be unaxially pressed and compressed uniformly at the same rate, such that the preforms 531 and 532 are processed simultaneously. In particular, the recesses 513 and 523 can be oriented with respect to the preforms 531 and 532 in the opposing mold portions 510 and 520 to facilitate suitable formation of features (e.g., reliefs) in the preforms 531 and 532 during pressing

While the exemplary mold pack 500 illustrated in FIG. 5 includes two mold portions 510 and 520, alternative embodiments can include more than two mold portions. For example, a mold pack may include at least three molds. In another example, a mold pack may include at least four molds.

FIG. 6 is a cross- sectional illustration of a uniaxially hot pressing process according to an embodiment. In particular, the uniaxial hot pressing construction includes a mold construction 600 loaded with a preform 602, which can include any preforms described in embodiments herein. According to one embodiment, the mold construction 600 can include a mold 630 having an upper portion 608 and a lower portion 609 having the features of upper and lower portions described in embodiments herein. The mold construction 600 can also include die portions 660 and 661 configured to contain a least a portion of the preform 602 within the mold

construction 600, and may directly contact a portion of the preform 602 along its sides during a pressing operation. The mold construction 600 may further include an upper punch 662 that can be positioned above the upper portion 608, and in particular, can directly contact the upper portion 608 during a pressing operation. The mold construction 600 can further include a lower punch 663 that can be positioned below the lower portion 609, and in particular, can be in direct contact with the lower portion 609 during a pressing operation.

During a uniaxial pressing operation, a force (illustrated as "F" in FIG. 6) may be applied to the preform 602 along an axis of pressing (illustrated as "A" in FIG. 6). In particular, during a pressing operation, a force F can be applied along the single pressing axis A on the upper punch 662 to compact the preform 602 between the upper and lower portions 608 and 609. It will be appreciated that a force applied to a body may be translated into a pressure, depending upon the cross-sectional dimensions of the preform 602. Alternatively, two opposing forces can be applied from the top and bottom of the mold construction 600, such as equal and opposing forces on the upper punch 662 and the lower punch 663 to compact the preform 602 between the upper and lower portions 608 and 609. For illustrative purposes only, one preform 602 is illustrated as loaded into the mold 630. However, it will be appreciated that the mold 630 can be formulated to contain more than one preform, as described in embodiments herein. In this case, a plurality of abrasive bodies may be produced from multiple preforms in a single pressing operation. The forming process can include particular forming parameters. For example, the pressure applied may be dependent in part upon various factors, including but not limited to, particular components within the preform, content of phases within the preform, amount of shrinkage intended between the preform and the finally-formed bonded abrasive article, the temperature applied, the atmosphere, and the like. According to one embodiment, a preform 602 that includes bonding material comprising metal can be uniaxially hot pressed at a pressure of at least about 4.9 MPa (710 psi). In other embodiments, the force applied during the uniaxial hot pressing operation can be a pressure on the preform 602 of at least about 9.8 Mpa (1421 psi), such as at least about 14.7 MPa (2132 psi), or even at least about 19.6 MPa (2842 psi). Still, according to one embodiment, the pressure may be not greater than about 44.1 MPa (6398 psi), such as not greater than about 39.2 MPa (5685 psi), not greater than about 34.3 MPa (4975 psi), or even not greater than about 29.4 MPa (4264 psi). It will be appreciated that the preform 602 that includes a binding material comprising metal may be uniaxially hot pressed at a pressure within a range including any of the minimum and maximum values noted above.

Uniaxial hot pressing may be conducted in a particular atmosphere. For example, in one process according to an embodiment, the preform 602 can be uniaxially hot pressed in an atmosphere comprising air. In another example, the preform 602 can be uniaxially hot pressed in an inert atmosphere. It will be appreciated that an "inert atmosphere" refers to an atmosphere that does not include gases that may react with the components of the preform 602 during pressing. In another example, the preform 602 can be uniaxially hot pressed in an oxidizing atmosphere. Alternatively, the preform 602 may be uniaxially hot pressed in a reducing atmosphere. According to one embodiment, uniaxial hot pressing can include application of heat simultaneously with the application of a uniaxial force. The forming process can include particular forming temperature, which may be dependent in part upon various factors, including but not limited to, particular components within the preform, content of phases within the preform, amount of shrinkage intended between the preform and the finally-formed bonded abrasive article, the temperature applied, the atmosphere, and the like.

For example, for a preform 602 including a bonding material comprising metal, the uniaxial hot pressing can be conducted at a temperature of at least about 600 °C (1112 °F), such as at least about 650 °C (1202 °F), at least about 700 °C (1292 °F), or even at least about 750 °C (1382 °F). In a particular embodiment, the temperature may be not greater than about 1100 °C (2012 °F), such as not greater than about 1000 °C (1832 °F), not greater than about 900 °C (1652 °F), or even not greater than about 800 °C (1472 °F). It will be appreciated that uniaxially hot pressing may be conducted at a temperature within a range including any of the minimum and maximum temperatures noted above. During the pressing operation, the preform 602 may be heated to a temperature such that the preform 602 is formed through a liquid phase sintering process. It will be appreciated that liquid phase sintering is a method of sintering, wherein at least a portion of one phase of the preform 602 (e.g., a portion of the bonding material) melts or becomes liquid. Notably, liquid phase sintering can also include the densification of the preform 602 into a finally-formed abrasive article. In one embodiment, liquid phase sintering can include changing at least a portion of the bonding material composition of the preform 602 into a liquid phase, wherein the liquid can change location within the mold 630 and facilitate changing the geometry of the preform 602 during the pressing operation. In particular instances, the combination of the composition of the preform 602 and the pressing operation can facilitate movement of the liquid phase through the preform 602 via capillary action to rearrange the unmelted particles into a more favorable packing arrangement.

Notably, during uniaxial hot pressing, a portion of the bonding material of the preform 602 may soften or melt, allowing a portion of the bonding material and abrasive particles to flow into one or more recesses of the mold 630, resulting in a substantial change in the geometry of the preform 602. The liquid phase of the bonding material may carry unmelted portions of the bonding material and unmelted abrasive grains into the recess. For example, the geometry of at least one surface of the preform 602 may be substantially altered during uniaxial hot pressing to include a relief projecting from a surface. According to a particular embodiment, at least a portion of the preform 602 can undergo liquid phase sintering and the liquid portion can flow into a recess (e.g., recess 304 of FIG. 3a) that is in fluid communication with an opening formed between upper and lower portions, wherein the preform 602 is disposed within the opening.

In this manner, a net-shaped or near net-shaped abrasive body may be formed during the uniaxial hot pressing operation. It will be appreciated that a "net-shaped" abrasive body is one that has a geometry that is essentially the same as the intended shape provided by the mold 630 when the pressing operation is completed. A "net- shaped" abrasive body may not necessarily require further shape-altering processing. A "near net-shaped" abrasive body is one that has a geometry that is essentially the same as the intended shape provided by the mold 630 when the pressing operation is completed and may require final processing, albeit minimal final processing.

FIG. 7 includes an exemplary embodiment of a mold 700 after uniaxial hot pressing is completed and a finally-formed abrasive body is formed according to an embodiment. In particular, the mold 700 includes an arrangement of an upper portion 708, a lower portion 709, a rear portion 710, and a finally-formed abrasive body 702 contained within the mold 700. As illustrated in FIG. 7, and according to one embodiment, after conducting the uniaxial hot pressing operation, the geometric dimensions of the preform have changed, such that the finally-formed abrasive article can include a relief 706, which is disposed into a recess 704 of the rear portion 710, and in particular, the relief 706 can have a complementary shape to the shape of the recess 704. Accordingly, the relief 706 can have a three-dimensional shape corresponding to the shape of the recess 704.

FIG. 8 depicts an exemplary embodiment of a loaded mold pack 800 after conducting a uniaxial hot pressing operation. As will be appreciated, the loaded mold pack 800 can include multiple molds 810 and 820 suitable for forming multiple preforms into finally-formed abrasive articles 831 and 832 in a single uniaxial hot pressing operation. As described in embodiments herein, the uniaxial hot pressing operation can be conducted in a manner to facilitate a change in geometric shape to the preforms, such that at least one geometric dimension of the finally-formed abrasive articles 831 and 832 is different than a geometric dimension of the corresponding preforms. In particular, as illustrated in FIG. 8, the finally-formed abrasive article 831 can have a relief 806 formed within and having a shape complementary to the recess 812. The finally-formed abrasive article 832 can have a relief 807 formed within and having a shape complementary to the recess 813.

FIG. 9a includes an illustration of an abrasive article according to an embodiment. In particular, the abrasive article can include an abrasive body 900 defined by a top surface 902 and a bottom surface 904 opposite the top surface 902, which are separated by a length (L) of the abrasive body 900. In particular instances, the top surface 902 and the bottom surface 904 may have curved contours, and particularly, may define convex and concave surfaces, respectively. The abrasive body 900 can also include a side surface 927 extending at an angle to a front surface 925 and a rear surface 926, which may be a substantially orthogonal angle, and join the front surface 925 and the rear surface 926. The abrasive body 900 can also include a side surface 928, spaced apart from the side surface 927 by the width (W) of the body 900. The side surface 928 can extend at an angle to the front surface 925 and the rear surface 926, which may be a substantially orthogonal angle, and join the front surface 925 and the rear surface 926.

The abrasive body 900 can also be defined by a front surface 925 and a rear surface 926, separated from each other by a thickness (T). Notably, the abrasive body 900 can include a relief 990 in the form of a projection extending from the front surface 925. In particular instances, the relief 990 can be defined by a first surface 991 extending at an angle from the front surface 925 and a second surface 992 extending at an angle from the front surface 925 and spaced apart from the first surface 991 by a third surface 993. As illustrated, a first angle 995 can be defined between the first surface 991 and the third surface 993. The first angle 995 can be an acute angle, an obtuse angle, or a substantially orthogonal angle. According to the illustrated embodiment of FIG. 9a, the first angle 995 defines a substantially orthogonal angle. As also illustrated, a second angle 996 can be defined between the second surface 992 and the third surface 993. The second angle 996 can be an acute angle, an obtuse angle, or a substantially orthogonal angle. According to the illustrated embodiment of FIG. 9a, the second angle 996 defines a substantially orthogonal angle.

As will be further appreciated, while the relief 990 is illustrated as having a particular cross-sectional polygonal shape, such that angles are defined between certain surfaces, other surfaces can be used to define other particular polygonal shapes. For example, the relief 900 can have a cross-sectional shape that is triangular, quadrilateral, pentagonal, hexagonal, or any other polygonal shape. Further, a quadrilateral relief can be a parallelogram, such as a rhombus, a rhomboid, a rectangle, or a square. Moreover, the quadrilateral relief can be a trapezoid, a trapezium, or an isosceles trapezoid. In another aspect, the relief 990 can be defined by one or more curvilinear surfaces, such that radiuses or rounded edges are utilized and the relief 990 can have a cross-sectional shape that is semicircular. Further, the relief can be formed into patterns that can include wording, letters, numbers, symbols, alphanumeric symbols, etc. In a particular aspect, the patterns formed by the relief can be used to identify the part in which the relief is formed.

According to an embodiment, the relief 990 can extend for at least a portion of the width (W) of the abrasive body 900 between the side surfaces 927 and 928. In another embodiment, the relief 990 can extend for a full dimension of the width (W) of the body 900, such that the relief 990 intersects the side surfaces 927 and 928. Furthermore, as illustrated, the relief 990 can be formed such that the surfaces 991, 992, and 993 have a curvature extending along the width (W) of the abrasive body 900. In particular, the surfaces 991, 992, and 993 defining the relief 990 can have a same curvature extending along the dimension of the width (W), and define a same arc as the curvatures of the top and bottom surfaces 902 and 904 of the abrasive body 900.

FIG. 9b includes a perspective view of the abrasive body 900. As illustrated, the abrasive body 900 can have an asymmetry in a plane 950 defined by the dimensions of the length (L) and the thickness (T) of the abrasive body 900. Notably, the relief 990 can extend at an angle from the front surface 925 and define an asymmetry to a plane that is parallel with an axis of pressing. In more detail, FIG. 9c includes a cross-sectional view of the abrasive body 900 along the plane 950. As illustrated, the body 900 can include a relief 990 extending from the front surface 925, which is an exterior surface of the body 900, and define a plane 951 parallel to the axis (A) of force applied during the uniaxial hot pressing operation.

In a one embodiment, the relief 990 may include a design on the surface of the abrasive body 900. For example, the relief 990 may include indicia, including for example, a logo, such as a company logo, a product logo, product number, or serial number. In particular instances, the relief 990 may be the indicia, including for example, a logo, such as a company logo, a product logo, product number, or serial number.

FIGs. 10a, 10b, and 10c include illustrations of abrasive articles according to embodiments herein. In particular, the abrasive articles include abrasive bodies demonstrating alternative designs according to embodiments. For example, FIG. 10a includes an illustration of an abrasive article including a body 1000 having a relief

1090 extending from the body 1000 at a right angle "R" to the axis of pressing A. That is, the relief 1090 of FIG. 10a can define a right angle R between a first surface

1091 and a front surface 1025. As another example, FIG. 10b includes an illustration of an abrasive article including a body 1051 having a relief 1090 extending from the body 1051 at an acute angle "C" relative to the axis of pressing A. That is, the relief 1090 of FIG. 10b can define an acute angle C between the first surface 1091 and the front surface 1025 of the body 1051. Accordingly, as illustrated, the relief 1090 may extend upward toward a top surface 1002 of the body 1051.

In a further example, FIG. 10c includes an illustration of an abrasive article including a body 1052 having a relief 1090 extending from the body 1052 at an obtuse angle "O" relative to the axis of pressing A. That is, the relief 1090 of FIG. 10c can define an obtuse angle C between the first surface 1091 of the relief 1090 and the front surface 1025 of the body 1052. Accordingly, as illustrated, the relief 1090 may extend downward toward a bottom surface 1004 of the body 1052. In a particular embodiment, prior to the forming process, the preform may include a particular content of porosity. For example, the preform can include at least about 20 vol% porosity, such as at least about 25 vol% porosity, at least about 30 vol% porosity, or even at least about 35 vol porosity for the total volume of the preform. Still, the preform may include not greater than about 60 vol% porosity, such as not greater than about 55 vol% porosity, not greater than about 50 vol% porosity, or not greater than about 45 vol% porosity for the total volume of the preform. It will be appreciated that the preform may include a porosity content within a range including any of the minimum and maximum values provided above According to another particular embodiment, upon completion of the forming process on the preform, the resulting abrasive body may include 0 vol% porosity. In another embodiment, the body may include a particular content of porosity. For example, the body may include at least about 1 vol porosity, such as at least about 3 vol% porosity, at least about 5 vol% porosity, or even at least about 10 vol% porosity for the total volume of the body. Still, the body may include not greater than about 20 vol% porosity, such as not greater than about 15 vol% porosity for the total volume of the body. It will be appreciated that the body may include a porosity content within a range including any of the minimum and maximum values provided above. According to another embodiment, upon completion of the forming process, the abrasive body may include a particular content of bonding material. For example, the body may include at least about 10 vol% bonding material for the total volume of the body. In certain other instances, the body can include at least about 15 vol bonding material, at least about 20 vol% bonding material, or even at least about 25vol% bonding material. Still, the body may include not greater than about 70 vol bonding material, such as not greater than about 65 vol% bonding material for the total volume of the body. It will be appreciated that the body may include an amount of bonding material within a range including any of the minimum and maximum values provided above. EXAMPLE In a particular embodiment, for uniaxial hot pressing along a length, L, of a preform, the length, L, is selected by considering, for example, the compactibility of the mixture that comprises the preform and the expected life of the compaction tools used to form the preform. The final length of the preform should be selected such that wear on the compaction tools due to the abrasive particles in the preform mixture is limited while providing sufficient compaction so the preform is sufficiently strong enough to be handled readily without breaking when placed in a mold. For a bonding material comprising 30-100 wt% bronze and 40-60 wt% iron and a final abrasive content of 2-12.5 vol% (as measured in the final abrasive body), the compaction pressure can be within a range that is between and includes about 68.9 Mpa (10.0 ksi) to about 441.3 MPa (64.0 ksi), the hot pressing temperature can be within and include a range of about 600 °C (1112 °F) to about 1100 °C (2012 °F), and the hot pressing pressure can be within and include a range of about 4.9 MPa (710 psi) to about 44.1 MPa (6398 psi). In one instance, an abrasive body includes a preform mixture that includes: a bonding material having 40 wt% electrolytic iron powder (-315 mesh), 48 wt% water atomized pre-alloyed bronze 90/10 (-200 mesh), and 12 wt% nickel base alloy (53-75 μιη);

3.5 vol of diamond grit abrasive particles; and 5.0 vol of graphite powder lubricant additive (50-150 mesh).

The preform mixture is compacted at a compaction pressure of about 372 MPa (54 ksi) to form a preform that includes a length that is about 1.8 times greater than the final abrasive body. The preform is hot pressed at a temperature of about 900 °C (1652 °F) and a pressure of about 19.6 MPa (2842 psi) to form the abrasive body. The embodiments herein represent a departure from the state-of-the-art.

Traditionally, bonded abrasive articles are formed through processes such as cold pressing or hot pressing. In such processes, forces are applied evenly across the surface of the preform to form the finally-formed abrasive body. Moreover, with respect to uniaxial pressing operations, such a process is reserved in the industry for those materials having uniform compositions. Materials having heterogeneous compositions are regarded as having differential compaction dynamics that can result in density gradients within the finally- formed body and thus a poorly formed and unfit article. However, the present embodiments are directed to uniaxial hot pressing of heterogeneous bodies including abrasive particles and bonding material to form bonded abrasive articles. The embodiments herein utilize a combination of features, which include, but are not limited to, compositions of the preform, shape of the preform, composition and shape of the molds, processing parameters including pressure, temperature, and atmosphere, liquid phase sintering, and changes in geometry between the preform and finally-formed abrasive article, which facilitate the forming process and attributes of the finally-formed bonded abrasive bodies.

In the foregoing, reference to specific embodiments and the connections of certain components is illustrative. It will be appreciated that reference to components as being coupled or connected is intended to disclose either direct connection between said components or indirect connection through one or more intervening components as will be appreciated to carry out the methods as discussed herein. As such, the above-disclosed subject matter is to be considered illustrative, and not restrictive, and the appended claims are intended to cover all such modifications, enhancements, and other embodiments, which fall within the true scope of the present invention. Thus, to the maximum extent allowed by law, the scope of the present invention is to be determined by the broadest permissible interpretation of the following claims and their equivalents, and shall not be restricted or limited by the foregoing detailed description.

The Abstract of the Disclosure is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. In addition, in the foregoing Detailed Description, various features may be grouped together or described in a single embodiment for the purpose of streamlining the disclosure. This disclosure is not to be interpreted as reflecting an intention that the claimed embodiments require more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive subject matter may be directed to less than all features of any of the disclosed embodiments. Thus, the following claims are incorporated into the Detailed Description, with each claim standing on its own as defining separately claimed subject matter.

Claims

WHAT IS CLAIMED IS:

1. A method of forming a bonded abrasive body comprising: uniaxially hot pressing a preform comprising abrasive particles in a bonding material to form a bonded abrasive body.

2. The method of claim 1, wherein during uniaxially hot pressing, the geometry of the preform is substantially altered.

3. The method of claim 1, wherein uniaxially hot pressing comprises liquid phase sintering.

4. The method of claim 1, further comprising uniaxially hot pressing at a temperature within a range of about 600 °C (1112 °F) to about 1100 °C (2012 °F).

5. The method of claim 1, further comprising uniaxially hot pressing at a pressure of within a range of about 4.9 MPa (710 psi) to about 44.1 MPa (6398 psi).

6. The method of claim 1, wherein the abrasive particles comprise a material selected from the group consisting of an oxide, a carbide, a nitride, a boride, an oxynitride, an oxycarbide, and a combination thereof.

7. The method of claim 1, wherein the abrasive particles comprise a superabrasive.

8. The method of claim 7, wherein the superabrasive comprises diamond.

9. The method of claim 7, wherein the superabrasive comprises cubic boron nitride (CBN).

10. The method of claim 1, further comprising placing the preform in a mold prior to pressing.

11. The method of claim 1 or 12, further comprising pressing at least two preforms simultaneously.

13. The method of claim 1 or 14, wherein pressing forms a net- shaped bonded abrasive body.

15. The method of claim 1 or 16, wherein pressing forms a near net-shaped bonded abrasive body.

17. The method of claim 1 or 18, further comprising forming a green body preform comprising abrasive particles and a bonding material.

19. The method of claim 17, wherein forming the green body preform comprises cold pressing a mixture of the abrasive particles and the bonding material.

20. The method of claim 1, 21 or 22, wherein the bonded abrasive body comprises a relief.

23. The method of claim 1, 24 or 25, further comprising forming a relief projecting from a surface of the bonded abrasive body, wherein the relief extends at an angle from a plane extending parallel to an axis of pressing.

26. A method of forming a body comprising:

uniaxially hot pressing a preform comprising abrasive particles to form a body having a relief extending from a plane which extends parallel to an axis of pressing.

27. The method of claim 1, 10, 14 or 26, further comprising forming the body such that the final shape of the body is asymmetric around the axis of pressing.

28. The method of claim 26, wherein the plane defines an exterior surface of the body.

29. The method of claim 26, wherein uniaxially hot pressing comprises forming a relief in the body during pressing, wherein the relief extends at an angle to the axis of pressing.

30. The method of claim 29, further comprising forming the relief extending at an acute angle to the axis of pressing.

31. The method of claim 29, further comprising forming the relief extending at an obtuse angle to the axis of pressing.

32. The method of claim 29, wherein forming comprises forming the relief extending perpendicular to the axis of pressing.

33. The method of claim 26, further comprising substantially altering the geometry of the preform during pressing.

34. The method of claim 26, wherein uniaxially hot pressing comprises liquid phase sintering.

35. The method of claim 26, further comprising uniaxially hot pressing at a temperature within a range of about 600 °C (1112 °F) to about 1100 °C (2012 °F).

36. The method of claim 26, further comprising uniaxially hot pressing at a pressure within a range of about 4.9 MPa (710 psi) to about 44.1 MPa (6398 psi).

37. The method of claim 1, 10, 14 or 26, further comprising uniaxially hot pressing in one of an oxidizing atmosphere, a reducing atmosphere, or an inert atmosphere.

38. The method of claim 37, further comprising uniaxially hot pressing in an inert atmosphere.

39. The method of claim 26, wherein the body comprises a composite.

40. The method of claim 39, wherein the body comprises a bonding material.

41. The method of claim 1, 10, 14, 18 or 40, wherein the bonding material comprises an inorganic material.

42. The method of claim 41, wherein the bonding material comprises a ceramic.

43. The method of claim 41, wherein the bonding material comprises a metal or a metal alloy.

44. The method of claim 43, wherein the bonding material comprises a transition metal element.

45. The method of claim 1 , 10, 14, 18 or 40, wherein the bonding material comprises a vitreous material.

46. The method of claim 1, 10, 14, 18 or 40, wherein the bonding material comprises an organic material.

47. The method of claim 1, 10, 14, 18 or 40, wherein the bonding material comprises a polymer.

48. The method of claim 1, 10, 14, 18 or 40, wherein the bonding material comprises a material selected from the group consisting of a resin, glycol, dextrin, polyethylene, ethylene, propylene, polyvinyl alcohol, and a combination thereof.

49. The method of claim 48, wherein the bonding material comprises a resin.

50. The method of claim 39, wherein the body comprises a ceramic.

51. The method of claim 39, wherein the body comprises a bonded abrasive body.

52. The method of claim 26, wherein the abrasive particles comprise superabrasive particles.

53. The method of claim 52, wherein the abrasive particles comprise a material selected from the group consisting of an oxide, a carbide, a nitride, a boride, an oxynitride, an oxycarbide, and a combination thereof.

54. The method of claim 52, wherein the superabrasive comprises diamond.

55. The method of claim 52, wherein the superabrasive comprises cubic boron nitride (CBN).

56. The method of claim 26, further comprising placing the preform in a mold prior to pressing.

57. The method of claim 26, further comprising pressing at least two forms simultaneously.

58. The method of claim 26, wherein pressing forms a net-shaped body.

59. The method of claim 26, wherein pressing forms a near net-shaped body.

60. The method of claim 26, further comprising forming a green body preform comprising abrasive particles and a bonding material.

61. The method of claim 60, wherein forming the green body preform comprises cold pressing the abrasive particles and bonding material.

62. The method of claim 1, 10, 14 or 26, wherein the preform comprises approximately 20-60 vol% porosity.

63. The method of claim 1, 10, 14 or 26, wherein the body comprises at most approximately 0-20 vol porosity.

64. A method of forming a bonded abrasive body comprising: forming a green body comprising abrasive particles and a bonding material; placing the green body in a mold; and

uniaxially hot pressing the green body to form a bonded abrasive body.

65. A method of forming a bonded abrasive body comprising:

forming a mixture of abrasive particles and bonding material;

forming the mixture into a green body;

placing the green body in a mold; and

pressing the mold to form a bonded abrasive body with a near net shape, wherein pressing comprises uniaxial hot pressing and wherein the bonded abrasive body has a shape which is asymmetric around the pressing axis.

66. A method of forming a composite body comprising:

uniaxially hot pressing a green body preform to form a composite body, wherein pressing comprises liquid phase sintering and wherein during pressing the geometry of the preform is substantially altered.

67. The method of claim 66, wherein during pressing at least one contour of a surface of the preform changes shape.

68. The method of claim 66, wherein during pressing an extension is formed protruding from a surface of the composite body.

69. The method of claim 68, wherein the extension extends from a surface of the body at an angle to an axis of pressing.

70. The method of claim 69, wherein the angle is an acute angle.

71. The method of claim 69, wherein the angle is an obtuse angle.

72. The method of claim 69, wherein the angle is perpendicular to the axis of pressing.

73. The method of claim 88, wherein pressing comprises uniaxially hot pressing at a temperature within a range of about 600 °C (1112 °F) to about 1100 °C (2012 °F).

74. The method of claim 66, further comprising pressing at a pressure within a range of about 4.9 MPa (710 psi) to about 44.1 MPa (6398 psi).

75. The method of claim 66, further comprising pressing in one of an oxidizing atmosphere, a reducing atmosphere, or an inert atmosphere.

76. The method of claim 75, further comprising pressing in an inert atmosphere.

77. The method of claim 66, further comprising placing the green body preform in a mold prior to pressing.

78. The method of claim 1, 21, 48 or 77, wherein the mold comprises a recess for forming the relief.

79. The method of claim 1, 21, 48 or 77, wherein the mold comprises carbon.

80. The method of claim 1, 21, 48 or 77, wherein the mold is carbon-based.

81. The method of claim 1, 21, 48 or 77, wherein the mold consists essentially of carbon.

82. The method of claim 1, 21, 48 or 77, wherein the mold comprises graphite.

83. The method of claim 1, 21, 48 or 77, wherein the preform directly contacts the mold.

84. The method of claiml, 21, 48 or 77, further comprising providing a mold pack within a die wherein the mold pack comprises a plurality of molds and a plurality of green body preforms.

85. The method of claim 84, wherein providing a mold pack within a die comprises loading a mold of the plurality of molds with a green body preform of the plurality of green body preforms.

86. The method of claim 84, further comprising uniaxially hot pressing the mold pack.

87. The method of claim 66, further comprising pressing at least two green body preforms simultaneously.

88. The method of claim 66, further comprising forming the green body preform comprising a mixture of abrasive particles and a bonding material.