WO2011000348A1

WO2011000348A1 - Coating and method for coating a component

Info

Publication number: WO2011000348A1
Application number: PCT/DE2010/000708
Authority: WO
Inventors: Maik Zeugner; Jürgen RÖSING; Frank Seidel
Original assignee: Mtu Aero Engines Gmbh
Priority date: 2009-06-30
Filing date: 2010-06-21
Publication date: 2011-01-06
Also published as: DE102009031313B4; DE102009031313A1

Abstract

The invention relates to a coating (20) for or on a component (10), in particular for a blade of a turbo-machine, comprising a matrix material (28) and hard material particles (30), which contain at least either cubic boron nitride or silicon nitride or sialon, wherein the hard material particles (30) are coated.

Description

Coating and method for coating a component Description

The present invention relates to a coating for or on a component, in particular for or on a blade for a turbomachine, and to a method for coating a component. Axial compressors and gas turbines, such as used in gas turbine engines for aircraft or other mobile or stationary applications, typically include multiple stages with rotating blades and fixed vanes or stator vanes. The rotor blades are rigidly connected to a rotor and rotate with it at high speed about an axis.

An essential feature of axial compressors and gas turbines are the pressure differences existing between the upstream side and the downstream side of each blade ring. Any pressure loss at the outer edge of a rotor blade ring or at the inner edge of a stator blade ring reduces the efficiency.

Due to high speeds, sometimes high temperatures, radial and axial deflections resulting from vibrations and different coefficients of expansion and temperatures of the components involved, mostly labyrinth seals or gap seals are used. For example, a sealing fin on the rotating component engages in a groove on the stationary component or vice versa.

The exact dimensions of the sealing fin and especially the groove are often not adjusted or created during production. Rather, for example, a blade tip digs into an inlet lining during an inlet process of the turbomachine and thus forms the corresponding groove there. For this purpose, the blade tip on an abrasive coating. EP 0 270 785 A2 discloses a coating of a blade tip with a mixture of powders of two MCrAlY alloys with different melting points. The coating is heated to a temperature above the melting temperature of one and below the melting temperature of the other MCrAlY alloy.

From WO 2007/115551 A1 a blade tip armor with a metallic adhesive layer and a metallic cover layer is known. The metallic cover layer has abrasive particles embedded in a metallic matrix material. The metallic adhesive layer and the metallic matrix material are each formed from an MCrA-IY material.

From US 5,359,770 a method for connecting an abrasive layer with a blade tip of a gas turbine is known. The abrasive layer contains alumina particles coated with a thin layer of reactive material.

WO 2008/135803 A1 discloses a method for coating a rotor blade tip of a gas turbine, in which first a layer of a powder of an alloy having a high melting point and abrasive particles and then a layer of a powder of an alloy having a low melting point are applied , Both are then heated to a temperature above the low and below the high melting temperature.

US Pat. No. 7,063,250 B2 discloses a solder coating and a method for producing a blade tip armor. The solder coating comprises a metallic solder layer, which has been added with boron, and a layer of material applied thereto, which contains CBN abrasive particles embedded in a binder and MCrAlY particles. This layer formation is applied in the form of an adhesive tape to the blade tip and heated together with the rotor blade in a vacuum oven to about 600 ° C until the binder of the material layer has volatilized. Subsequently, the furnace is heated above the melting temperature of the solder (about 1000 ° C), and the liquefied solder penetrates into the material layer. The boron of the solder layer diffuses into the MCrAlY particles and lowers their melting temperature. The MCrAlY particles are thereby melted into a Condition convoluted, allowing a mixture of MCrAlY alloy with the already liquid solder. When this process is complete, after cooling, a solid layer of CBN abrasive particles embedded in an MCrAlY matrix is formed. With the heating of the blade tip, however, there is still the risk of melting or crystallizing of the blade tip material.

It is an object of the present invention to provide an improved turbine blade tip topping and an improved blade topping method of a turbomachine.

This object is solved by the subject matters of the independent claims. Further developments are specified in the dependent claims. Various embodiments of the present invention are based on the idea of coating a component with a matrix material which is provided with corrosion protection, especially at high temperatures, and with coated hard material particles embedded in the matrix material and containing at least cubic boron nitride or silicon nitride or silicon oxynitride.

The matrix material is a material suitable for embedding the coated hard material particles, in particular a material which also has a corrosion protection at high temperatures, for example an MCrAlY alloy. The coated hard material particles can be embedded in the pure matrix material, or else in a mixture of the matrix material and another material, for example a solder. In the case of embedding the coated hard material particles in a mixture of the matrix material and the solder, this mixture may be a homogeneous or single-phase mixture or a heterogeneous or multiphase mixture. In the case of a multiphase mixture, for example, the matrix material is in the form of particles or of a powder which is embedded in the solder, with essential properties, such as the corrosion protection, being determined by the matrix material. In this case, components of the mat Rixmaterials be diffused into the solder and / or components of the solder in the matrix material.

The coating of the individual hard material particles is in particular selected and designed to facilitate a cohesive connection of the hard material particles with the matrix material. For this purpose, the hard-material particles are coated, for example, with a material which reacts chemically with the matrix material and / or, if appropriate, with a solder used for the coating, which is chemically similar to the matrix material or, if appropriate, to the solder or which, although not provided with the matrix material or If necessary, it reacts chemically with the solder, but due to its chemical and physical properties it is wetted by the matrix material or, if appropriate, by the solder.

The coating of the hard material particles has, for example, at least one of Ti, Cr, Hf, another reactive element, Ni, Co, Al or Fe. The coating may comprise exclusively or almost exclusively one or more of the named elements, the sum of the mass fractions of further elements being less than 10% or less than 5% or less than 1%. Alternatively, the coating comprises an alloy with one or more of said elements as main alloy components, wherein in particular the mass fractions of all further elements or even the sum of the mass fractions of all further elements are smaller than the mass fractions of the main alloy components.

The coating has, for example, a thickness of at most 50 μm or at most 20 μm or at most 10 μm. For many applications, a coating is advantageous whose mass is not greater than that of the uncoated hard material particle. The coating is applied in particular by CVD (chemical vapor deposition = chemical vapor deposition), PVD (physical vapor deposition = physical vapor deposition) or galvanically on the hard material particles. One advantage of this coating is that the excellent properties of cubic boron nitride, silicon nitride, and silicon aluminum oxynitride, which have been proven by the Applicant to be used on blades of turbomachinery in particular as hard material particles can now be combined with a fixed integration into the matrix material. This reduces the risk of melting or recrystallization of the material of the component. This is of great importance especially for the directionally solidified or monocrystalline materials used today for thermally and mechanically highly loaded blades of gas turbines or other turbomachines. At the same time or as an alternative, the coating of the hard material particles improves their incorporation into the material structure of the coating, in particular into the matrix material and / or the solder. The coated hard material particles of cubic boron nitride, silicon nitride or silicium aluminum oxynitride can be embedded or embedded in a layer which, apart from the coated hard material particles, essentially consists only of the solid matrix material, for example an MCrAlY alloy. Alternatively, the matrix material is originally present as a powder, which is mixed with the hard material particles at least on the surface of the coating.

For bonding the layer of the powder of the matrix material and the hard material particles, a solder can be used which wets the powder particles of the matrix material and the coated hard material particles at least after the application of the coating to the component and a corresponding thermal treatment, and the open-pore structure of the particles completely penetrates, so that the powder particles of the matrix material and the hard particles are embedded in the finished coating in the solder. To produce this structure, only the solder, but not the matrix material, has to be melted. As a result, the thermal load on the component during coating can be drastically reduced.

Regardless of whether the matrix material is present as a powder or in another solid form, the coating may comprise a solder for the material-locking connection of the matrix material to the component or a surface of the component. The solder is in particular a cobalt base solder having a cobalt mass fraction of at least 30% or at least 40%, preferably with a cobalt mass fraction of between 50% and 60%, in particular 55.6%. Regardless of the composition of the solder, it is advantageous for many applications. liable if the solidus temperature of the solder is below the solidus temperatures of the matrix material and the hard material particles.

The matrix material and the solder can be chosen such that at a predetermined temperature above the solidus temperature of the solder and below the solidus temperature of the matrix material at least either constituents of the matrix material (28) into the solder (23) or constituents of the solder (23) into the solder Diffuse matrix material (28). This can go to a breakdown of matrix material and material of the solder and to form a new alloy. As a result, the material properties of the solder and the material-o-positive connection between the solder and the powder particles of the matrix material can be further improved. The matrix material has, for example, the following mass fractions: 22% ± 5% (in particular approx. 22.5%) Cr; 10% ± 2% (especially about 10%) Al; 0.5% to 1.5% Y. Remaining mass fractions can be formed by any metals or even non-metals, in the case of the matrix material, in particular Ni.

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The coating may comprise a layer structure having a first layer and a second layer, wherein the first layer comprises the solder, and wherein the second layer comprises the matrix material or the matrix material and the hard material particles. The layer structure may further comprise a third layer whose composition is different from the compositions of the first layer and the second layer and which is disposed between the first layer and the second layer. For example, the third layer and / or a fourth or fifth or further layer each have a mixture of solder and a matrix material or a mixture of a solder, a matrix material and a hard material (in particular in particle form). Alternatively, alloys other than solder, matrix material or hard material may be present in the third, fourth, fifth or further layer, for example. For example, by using different particle fractions in different layers positive properties can be achieved with respect to segregation effects. Alternatively or additionally, the setting of an optimized thermal expansion system is possible.

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Although such a multi-layered structure consisting of - not counting an adhesive layer for preliminary fixation prior to a thermal treatment - three or more layers conventional lent because of the increased manufacturing effort was not previously considered, it was found that especially with such a multilayer structure of the coating particularly defined and advantageous properties of the coating can be achieved.

Alternatively, however, the coating may also have a predetermined variation in composition continuous in the direction of its thickness. Furthermore, the coating may alternatively or additionally comprise a predetermined predetermined variation of the composition in the lateral direction or in the direction parallel to the coating and perpendicular to the direction of the thickness of the coating. For example, a lateral variation in composition allows for lateral variation of the abrasive properties or other properties of the coating. For example, the proportion of the solder decreases from the side facing the component to the side facing away from the component, the proportion of the hard material particles increases in the same direction and the proportion of the matrix material has a maximum in between. Such continuous variation of the composition enables a particularly strong structure with a particularly low risk of detachment of individual layers.

The coating may have the properties described above both before application to the component (for example in the form of a tape, in particular adhesive tape, or a film, in particular adhesive film) as well as after application or after a thermal

Treatment for cohesive connection with the component have.

The present invention further includes a blade for a turbomachine having one of the above-described coatings on one blade tip (which may be a squealer surface) and / or on another squealer surface. The coating can act there in particular as wear protection.

In a method for coating a blade for a gas turbine or other turbomachine, a matrix material and hard material particles containing and coated at least either cubic boron nitride or silicon nitride or silicon aluminum oxynitride are applied to the component and by local heating of the blade tip the matrix material and the hard particles with the component joined materially or connected. The local heating or heating of the blade tip takes place, for example, by ohmic losses of inductively induced eddy current fields.

The cohesive joining comprises, for example, a melting of a solder, a wetting of at least the component and the matrix material, optionally also the coated hard material particles, by the solder and a solidification of the solder. By diffusion of constituents of the solder and / or the matrix material and / or the material of the hard material particles, a partial or complete homogenization with regard to the composition can take place. As a result, one or more new alloys can arise, which have different solids and / or liquidus temperatures. For example, the isothermal solidification of the system of solder and matrix material is possible.

The application of the matrix material and the hard material particles may include applying a tape, a wire, a foam or a film with the matrix material to the hard particles and optionally the solder. In particular, both the matrix material and the optional solder are in each case in a solid state of aggregation, for example as a powder or in the form of a band, a wire, a foam, a film or another semifinished product. Already before or even after the cohesive bonding, optionally already in the tape or in the film, the concentrations of the matrix material, the hard material particles and optionally the solder in the direction of the thickness of the coating can vary continuously. Alternatively, the coating may comprise a layered structure having a first layer, a second layer, and optionally a third layer. The first layer may optionally comprise the solder, the second layer may comprise the hard material particles, and optionally the third layer may be arranged between the first layer and the second layer and have a different composition than the first layer and the second layer. Alternatively, the coating or parts of the coating described-in particular individual layers-can be applied by thermal spraying, painting, printing or other means. In particular, one of the coatings described above can be applied using the described method.

Brief description of the figures

Embodiments will be explained in more detail with reference to the accompanying figures. Show it:

Figure 1 is a schematic representation of a cross section of a component and a coating to be applied to the component;

Figure 2 is a schematic representation of a cross section of a coated hard particle;

Figure 3 is a schematic representation of a cross section of a further coating; Figure 4 is a schematic representation of a cross section of a further coating;

Figure 5 is a schematic flow diagram of a method for coating a

Component.

Description of the embodiments

FIG. 1 shows a schematic illustration of a cross section of a component 10 with a surface 12 to be coated and a coating 20 present here in the form of a film and to be applied to the surface 12 of the component 10 to be coated. The illustrated sectional plane lies - as in FIGS and 4 - vertical or in Substantially perpendicular to the surface to be coated 12 and parallel to the normal to the plane of the largest extent of the coating 20. The coating 20 is spaced from the surface to be coated 12 and thus in an arrangement immediately prior to applying the coating 20 to the surface to be coated 12 is shown.

The component 10 is in particular a blade of a turbomachine or for a turbomachine. Shown in Figure 1 is primarily the blade tip of the blade. The reference numeral 10 denotes insofar is especially the blade tip.

The coating 20 has an adhesive layer 21 which faces the surface 12 to be coated. The adhesive layer 21 comprises, for example, an organic adhesive. By means of the adhesive layer 21, the coating 20 can first be stapled to the surface 12 to be coated. The adhesive layer 21 is designed such that it disappears without residue or substantially without residue in a subsequent thermal treatment.

The coating 20 further comprises a solder layer 22 with solder particles 23 in a matrix of an organic binder 24. Also, the binder 24 of the solder layer 22 is similar to the adhesive layer 21 formed to disappear in a subsequent thermal treatment without residue or substantially residue-free. The illustrated embodiment of the solder layer 22 in the form of solder particles 23 in a matrix of a binder 24 has a high elastic and especially plastic deformability and other manufacturing advantages. Alternatively, unlike the illustration in FIG. 1, the solder layer 22 is a layer of solid solder without a binder.

The coating 20 further comprises a functional layer 26 with a, in particular organic, binder 27. In the binder 27 are embedded MCrAlY particles 28 and hard material particles 30 containing at least either cubic boron nitride or silicon nitride or silicon aluminum mini oxynitride. Similar to the adhesive layer 21 and the binder 24 of the solder layer 22, the binder 27 of the functional layer 26 is in particular designed to be free of residue or in a subsequent thermal treatment. considerably disappear without leaving a trace. Alternatively, the functional layer 26 deviating from the illustration in Figure 1, no binder 27, instead, the MCrAlY alloy is solid and contains embedded Hartstofrpartikel 30. Instead of a MCrAlY alloy, the functional layer 26 - in the form of a powder or other solid form - Contain another suitable matrix material.

FIG. 2 shows a schematic representation of a cross section through a coated hard material particle 30. The hard material particle 30 has a coating 32 on its surface. The material of the coating 32 is chosen such that it forms a solid material connection with the material of the hard material particle 30 on the one hand and wetting of the hard material particle 30 by the matrix material and / or by the solder and a cohesive connection between the hard material particles 30 and the matrix material and / or the Lot promotes. This may be due to the chemical and / or physical properties of the material of the coating 32.

Although the hard material particles are shown in Figure 2 and also in Figures 1, 3 and 4 each with a square or rhombic cross-section, they may have any regular or irregular shape. Figure 3 shows a schematic representation of a cross section through a coating 20, which differs from the coating shown above with reference to Figure 1 in that it consists of - the adhesive layer 21 not included - three layers 22, 26, 34. As in the case of the coating illustrated above with reference to FIG. 1, here too the solder layer 22 comprises solder particles 23 in a binder 24. In contrast to the illustration in FIG. 3, the solder layer 22 may be a solid solder layer without a binder 24.

In contrast to the example shown above with reference to FIG. 1, the example shown in FIG. 3 has only MCrAlY particles 28 in the functional layer 26, but no hard material particles 30. Differing from the illustration in FIG. 3, the functional layer 26 can be an MCrAl Y Alloy (or other matrix material) in solid form without a binder 27. In contrast to the example shown above with reference to FIG. 1, the coating 20 shown in FIG. 3 also has a hard material particle layer 34. The hard material particle layer 34 comprises hard material particles 30, similar to those described above with reference to FIGS. 1 and 2, in an organic binder, for example. The binder 35 is also designed to be free of residue or substantially in a subsequent thermal treatment to disappear without residue.

4 shows a schematic representation of a cross section of a further example of a coating 20. Apart from an adhesive layer 21 similar to the adhesive layers of the examples illustrated above with reference to FIGS. 1 and 3, the coating 20 has only one layer, in the solder particles 23, MCrAl Y particles 28 and coated hard material particles 30 are arranged. The coated hard material particles 30 comprise at least one of either cubic boron nitride or silicon nitride or silicon aluminum oxynitride. The concentrations of the solder particles 23, the MCr Al Y particles 28 and the coated hard material particles 30 in a binder 24, in particular organic, vary in the direction of the thickness of the coating 20. The solder particles 23 have a side facing the surface of a component to be coated high concentration, which decreases towards the opposite side. The hard material particles 30 have a high concentration at the side facing away from the component to be coated, which decreases towards the side which is to be turned to the surface to be coated. The concentration of MCrAlY particles has a maximum in between.

FIG. 5 shows a schematic flow diagram of a method for coating a surface of a component, in particular a blade tip of a blade of an axial compressor, a gas turbine or another turbomachine. Although the method can also be carried out with coatings which differ from the examples described above with reference to FIGS. 1 to 4, reference numerals from FIGS. 1 to 4 are used by way of example in order to facilitate an understanding. In an optional first step 101, hard particles 30 of cubic boron nitride, silicon nitride or silicon aluminum oxynitride are coated. Alternatively, already coated hard material particles 30 are provided. The coating of the hard material particle Kel 30 is designed to facilitate or improve a wetting and a cohesive connection of the hard material particles 30 with a matrix material and / or a solder in subsequent process steps. In a second step 102, a solder is applied to a surface 12 to be coated of a component 10, for example in the form of a solid solder layer or in the form of solder particles 23, which are embedded in a binder 24. In a third step 103, a matrix material is applied to the surface 12 to be coated, for example in the form of a solid layer or in the form of a powder of the matrix material, which is embedded in a binder 27. In a fourth step 104, hard material particles 30 are applied to the surface 12 to be coated. The hard material particles 30 are in the applied in the third step 103 matrix material or in a binder 27; 35; 24 embedded. The second step 102, the third step 103, and the fourth step 104 may be performed sequentially or partially or completely simultaneously. In particular, the second step 102, the third step 103 and the fourth step 104 may be carried out simultaneously by applying one of the layer structures in the form of a tape or a film as described above with reference to FIGS. 1, 3 and 4.

In a fifth step 105, the solder, the matrix material, the hard material particles and at least the surface 12 to be coated of the component 10 are heated, for example by ohmic losses of induced eddy current fields. In the process, adhesive layer 21 and binder 24, 27, 35 initially evaporate and / or decompose, if present. After evaporation of and / or decomposition of adhesive layer 21 and binder 24, 27, 35, the temperature is increased to such an extent that it exceeds the temperature Solidus temperature of the solder or solder particles 23, but below the solidus temperature of the matrix material or the powder particles 28 of the matrix material. In a sixth step 106, which proceeds almost simultaneously with the fifth step 105, the solder 23 melts and wets the surface 12 of the component 10 to be coated and also the matrix material and, if the matrix material is present as a powder, the hard material particles 30. The solder, the matrix material and that reached Temperature may be selected so that at a substantially concurrent seventh step 107, the matrix material dissolves at least partially in the solder.

In an eighth step 108, the temperature of the solder, the matrix material, the hard particles 30 and the surface 12 to be coated is lowered below the solidus point of the solder. The solder solidifies and forms a material connection between the surface to be coated 12 on the one hand and the matrix material and the hard material particles 30 on the other. The cohesive connection of the solder to the hard material particles 30 is direct if the matrix material is in the form of a powder which is penetrated by the liquid solder due to capillary forces. The cohesive connection of the solder with the hard material particles 30 is an indirect one, when the hard material particles 30 are embedded in a solid layer of the matrix material, unlike in FIGS. 1, 3 and 4.

Claims

Claims:

1. coating (20) for a component (10), in particular for a blade of a flow machine, comprising: a matrix material (28),

Hard material particles (30) containing at least cubic boron nitride or silicon nitride or silicon aluminum oxynitride, characterized in that the hard material particles (30) are coated.

2. Coating (20) according to claim 1, further comprising: a solder (23) for materially connecting the matrix material (28) with a surface to be coated (12) of the component (10).

A coating (20) according to claim 2, wherein the solder (23) contains cobalt with a mass fraction of at least 50%.

4. Coating (20) according to claim 2 or 3, wherein the solder (23) has a solidus temperature which is below the solidus temperatures of the matrix material (28) and the hard material particles (30).

5. The coating (20) of claim 4, wherein at a predetermined temperature greater than the solidus temperature of the solder (23) and less than the solidus temperature of the matrix material (28) at least one of the matrix material (28) in FIG diffuse the solder (23) or components of the solder (23) into the matrix material (28).

6. Coating (20) according to any one of claims 2 to 5, wherein the coating (20) comprises a layer structure having a first layer (22) and a second layer (26; 34), wherein the first layer (22) the solder ( 23), and wherein the second layer (26; 34) comprises the hard particles (30) or the matrix material (28) and the hard particles (30).

The coating (20) of claim 6, further comprising a third layer (26) having a composition different from the compositions of the first layer (22) and the second layer (34).

A coating (20) according to any one of the preceding claims, having a predetermined continuous variation in the composition of the coating (20) in the direction of the thickness of the coating (20) or parallel to the coating.

9. Coating (20) according to one of the preceding claims, wherein the matrix material (28) is originally present as a powder which is mixed with the hard material particles (30).

10. Coating (20) according to claim 9 in reference to one of claims 2 to 7, wherein the powder (28) of the matrix material and the Hartstofrpartikel (30) are embedded in the solder (23).

11. A blade (10) for a turbomachine, with a coating (20) according to one of the preceding claims on the blade tip.

A method of coating the blade tip (10) of a blade for a turbomachine, comprising the steps of applying (103; 104) a matrix material (28) and coated hard particles (30) containing at least cubic boron nitride or silicon nitride or silicon aluminum oxynitride; integrally bonding (106, 107, 108) the matrix material (28) and the hard material particles (30) with the blade tip (10) by locally heating the blade tip (10).

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13. The method of claim 12, wherein the integral bonding comprises reflowing (105) a solder, wetting (106) at least the blade tip (10) and the matrix material (28) through the solder (23) and solidifying (108) the solder (23).

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14. The method of claim 12 or 13, wherein the applying comprises applying a tape or a film with the matrix material (28) and the hard material particles (30). 5

15. The method of claim 14 when recited in claim 13, wherein the concentrations of the matrix material (28), the hard particles (30) and the solder (23) vary continuously across the thickness of the tape.

16. A method according to claim 13 or claim 14 when dependent on claim 13, wherein the applying comprises applying a layered structure to a first layer

Layer (22), a second layer (34) and a third layer (26), wherein the first layer (22) comprises the solder (23), wherein the second layer (34) comprises the hard material particles (30), and wherein the third layer (26) is disposed between the first layer (22) and the second layer (34).

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17. The method according to any one of claims 12 to 16, wherein a coating (20) according to any one of claims 1 to 10 is applied.