DE102009031313A1 - Coating and method for coating a component - Google Patents

Abstract

A coating (20) for or on a component (10), in particular for a blade for a turbomachine, comprises a matrix material (28) and hard material particles (30) which contain at least either cubic boron nitride or silicon nitride or silicon aluminum oxynitride, the hard material particles (30 ) are coated.

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 during an inlet operation of the turbomachine in an inlet lining and thus forms there the corresponding groove. For this purpose, the blade tip on an abrasive coating.

From the EP 0 270 785 A2 is a coating of a blade tip with a mixture of powders of two MCrAlY alloys with different melting points known. The coating is heated to a temperature above the melting temperature of one and below the melting temperature of the other MCrAlY alloy.

From the 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 a MCrAlY material.

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

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

From the US 7,063,250 B2 For example, a solder coating and a method of making a blade tip armor are known. 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 converted to a molten state, allowing for mixing of the 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. However, with the heating of the blade tip 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 aluminum 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 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, constituents of the matrix material may be diffused into the solder and / or constituents of the solder in the matrix material.

The coating of the individual hard material particles is in particular selected and designed in order 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 chemically reacts with the matrix material and / or optionally with a solder used for the coating, which is chemically similar to the matrix material or optionally to the solder, or indeed with neither the matrix material nor optionally with the solder chemically reacts, but is wetted because of its chemical and physical properties of the matrix material or optionally of 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 means of CVD (chemical vapor deposition = chemical vapor deposition), PVD (physical vapor deposition = physical vapor deposition) or galvanically on the hard material particles.

An advantage of this coating is that the outstanding properties of cubic boron nitride, silicon nitride and silicon aluminum oxynitride as hard material particles, which are proven especially for use on blades of turbomachinery by the Applicant, can now be combined with a solid incorporation into the matrix material. This reduces the risk of melting or recrystallization of the material of the component. This is of particular importance 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 silicon 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 completely penetrates the open-pored structure of the particles such that the powder particles of the matrix material and the hard particles in the finished coating are embedded 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 the coating can be drastically reduced.

Regardless of whether the matrix material is in the form of a powder or in another solid form, the coating may be a solder to the material Include connecting the matrix material with 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 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 may be selected such that at least either constituents of the matrix material (at a predetermined temperature above the solidus temperature of the solder and below the solidus temperature of the matrix material) ( 28 ) into the lot ( 23 ) or components of the lot ( 23 ) into the matrix material ( 28 ) diffuse. 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 cohesive 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.

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, in the third, fourth, fifth or further layer, for example, alloys other than solder, matrix material or hard material may be present. 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.

Although such a multi-layered structure of - not counting an adhesive layer for preliminary fixation prior to a thermal treatment - three or more layers have conventionally not been considered because of the increased manufacturing cost, it has been found that especially with such a multi-layered 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, lateral variation of the 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 a continuous variation of the composition enables a particularly firm 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.

The present invention further comprises 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 material particles the component joined or connected cohesively. 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 the lot and a stiffening of the lot. 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. This may result in one or more new alloys having different solidus 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, the hard material 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 above-described coatings 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:

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

2 a schematic representation of a cross section of a coated hard material particle;

3 a schematic representation of a cross section of another coating;

4 a schematic representation of a cross section of another coating;

5 a schematic flow diagram of a method for coating a component.

Description of the embodiments

1 shows a schematic representation of a cross section of a component 10 with a surface to be coated 12 and one here in the form of a film and on the surface to be coated 12 of the component 10 applied coating 20 , The sectional plane shown is - as well as the 3 and 4 Perpendicular or substantially perpendicular to the surface to be coated 12 and parallel to the normal to the plane of greatest extension of the coating 20 , The coating 20 is spaced from the surface to be coated 12 and thus in an arrangement immediately before the application of the coating 20 on the surface to be coated 12 shown.

The component 10 is in particular a blade of a turbomachine or for a turbomachine. In 1 is shown in the first place, the blade tip of the blade. The reference number 10 Insofar, in particular, is the blade tip.

The coating 20 has an adhesive layer 21 on, the surface to be coated 12 is facing. The adhesive layer 21 has, for example, an organic adhesive. By means of the adhesive layer 21 can the coating 20 first to the surface to be coated 12 be stapled. The adhesive layer 21 is designed so that it disappears residue-free or substantially residue-free in a subsequent thermal treatment.

The coating 20 also has a solder layer 22 with solder particles 23 in a matrix of an organic binder 24 on. Also the binder 24 the solder layer 22 is similar to the adhesive layer 21 designed to disappear residue-free or substantially residue-free in a subsequent thermal treatment. 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, the solder layer 22 deviating from the illustration in 1 a layer of solid solder without binder.

The coating 20 further includes a functional layer 26 with a, especially organic, binder 27 , In the binder 27 are MCrAlY particles 28 and hard particles 30 embedded at least one of either cubic boron nitride or silicon nitride or silicon aluminum oxynitride. Similar to the adhesive layer 21 and the binder 24 the solder layer 22 is also the binder 27 the functional layer 26 in particular designed to disappear residue-free or substantially residue-free in a subsequent thermal treatment. Alternatively, the functional layer has 26 deviating from the illustration in 1 no binder 27 Instead, the MCrAlY alloy is solid and contains embedded the hard particles 30 , Instead of a MCrAlY alloy, the functional layer 26 - In the form of a powder or in another solid form - contain another suitable matrix material.

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

Although the hard material particles in 2 and also in the 1 . 3 and 4 are each shown with a square or rhombic cross-section, they can have any regular or irregular shape.

3 shows a schematic representation of a cross section through a coating 20 that differ from the above based on the 1 The coating shown differs in that it is made - the adhesive layer 21 not counted - three layers 22 . 26 . 34 consists. As with the above based on the 1 The coating shown here also includes the solder layer 22 solder particles 23 in a binder 24 , Deviating from the illustration in 3 can the solder layer 22 a massive layer of solder without binder 24 be.

In contrast to the above based on the 1 example shown has in 3 Example shown in the functional layer 26 only MCrAlY particles 28 on, but no hard particles 30 , Deviating from the illustration in 3 can the functional layer 26 an MCrAlY alloy (or other matrix material) in solid form without a binder 27 exhibit.

In contrast to the above based on the 1 Example shown has in 3 shown coating 20 further, a hard material particle layer 34 on. The hard material particle layer 34 includes hard material particles 30 similar to the one above based on the 1 and 2 in an organic binder, for example 35 , Also the binder 35 is designed to disappear in a subsequent thermal treatment without residue or substantially residue-free.

4 shows a schematic representation of a cross section of another example of a coating 20 , The coating 20 points - except for an adhesive layer 21 similar to the adhesive layers of the above based on the 1 and 3 Examples shown - only one layer, in the solder particles 23 , MCrAlY particles 28 and coated hard particles 30 are arranged. The coated hard material particles 30 have at least either cubic boron nitride or silicon nitride or silicon aluminum oxynitride. The concentrations of the solder particles 23 , the MCrAlY particle 28 and the coated hard material particles 30 in a - especially organic - binder 24 vary in the direction of the thickness of the coating 20 , The solder particles 23 have on the side facing a surface of a component to be coated facing a high concentration, which decreases towards the opposite side. The hard material particles 30 have at the side facing away from the component to be coated on a high concentration, which decreases to the side, which is the surface to be coated, towards decreases. The concentration of MCrAlY particles has a maximum in between.

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 other turbomachine. Although the process is also practicable with coatings other than those described above 1 to 4 In the following, by way of example, reference numerals will be taken from FIGS 1 to 4 used to facilitate understanding.

In an optional first step 101 become hard particles 30 cubic boron nitride, silicon nitride or silicon aluminum oxynitride coated. Alternatively, already coated hard material particles 30 provided. The coating of the hard material particles 30 is formed to wetting and a cohesive connection of the hard material particles 30 with a matrix material and / or a solder facilitate or improve upon subsequent process steps.

In a second step 102 becomes a solder on a surface to be coated 12 a component 10 applied, for example in the form of a solid solder layer or in the form of solder particles 23 in a binder 24 are embedded. At a third step 103 becomes a matrix material on the surface to be coated 12 applied, for example in the form of a solid layer or in the form of a powder of the matrix material, into a binder 27 is embedded. At a fourth step 104 become hard particles 30 on the surface to be coated 12 applied. The hard material particles 30 are in the third step 103 applied matrix material or in a binder 27 ; 35 ; 24 embedded.

The second step 102 , the third step 103 and the fourth step 104 can be performed consecutively or partially or completely simultaneously. In particular, the second step 102 , the third step 103 and the fourth step 104 be executed simultaneously by one of the above based on the 1 . 3 and 4 layer structures shown in the form of a tape or a film is applied.

At a fifth step 105 become the solder, the matrix material, the hard particles and at least the surface to be coated 12 of the component 10 heated, for example by ohmic losses induced eddy current fields. In the process, the adhesive layer initially evaporates and / or decomposes - if present 21 and binder 24 . 27 . 35 , After evaporation and / or decomposition of adhesive layer 21 and binder 24 . 27 . 35 the temperature is raised so that it is above the solidus temperature of the solder or solder particles 23 but below the solidus temperature of the matrix material or powder particles 28 of the matrix material. At one almost simultaneously with the fifth step 105 expiring sixth step 106 the solder melts 23 and wets the surface to be coated 12 of the component 10 as well as the matrix material and - if the matrix material is present as a powder - the hard material particles 30 , The solder, the matrix material and the temperature reached can be selected so that in a substantially concurrent seventh step 107 the matrix material at least partially dissolves in the solder.

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

LIST OF REFERENCE NUMBERS

10

component

12

to be coated surface of the component 10

20

Coating, in particular as a tape or foil

21

adhesive layer

22

solder layer

23

solder particles

24

Binder of the solder layer 22

26

functional layer

27

Binder of the functional layer 26

28

MCrAlY particles

30

Hard particles

32

Coating of the hard material particle 30

34

Hard particle layer

35

Binder of the hard material particle layer 34

101

first step

102

second step

103

Third step

104

fourth step

105

fifth step

106

sixth step

107

seventh step

108

eighth step

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• EP 0270785 A2 [0006]
• WO 2007/115551 Al [0007]
• US 5359770 [0008]
• WO 2008/135803 A1 [0009]
• US 7063250 B2 [0010]

Claims (17)

Coating ( 20 ) for a component ( 10 ), in particular for a blade of a turbomachine, 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. Coating ( 20 ) according to claim 1, further comprising: a solder ( 23 ) for materially joining the matrix material ( 28 ) with a surface to be coated ( 12 ) of the component ( 10 ). Coating ( 20 ) according to claim 2, wherein the solder ( 23 ) Contains cobalt with a mass fraction of at least 50%. 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 ) lies. Coating ( 20 ) according to claim 4, wherein at a predetermined temperature greater than the solidus temperature of the solder ( 23 ) and smaller than the solidus temperature of the matrix material ( 28 ), at least either components of the matrix material ( 28 ) into the lot ( 23 ) or components of the lot ( 23 ) into the matrix material ( 28 ) diffuse. Coating ( 20 ) according to one of claims 2 to 5, wherein the coating ( 20 ) a layer structure with a first layer ( 22 ) and a second layer ( 26 ; 34 ), wherein the first layer ( 22 ) the lot ( 23 ) and wherein the second layer ( 26 ; 34 ) the hard material particles ( 30 ) or the matrix material ( 28 ) and the hard material particles ( 30 ) having. Coating ( 20 ) according to claim 6, further comprising a third layer ( 26 ) whose composition differs from the compositions of the first layer ( 22 ) and the second layer ( 34 ) is different. Coating ( 20 ) according to one of the preceding claims, with a predetermined continuous variation of the composition of the coating ( 20 ) in the direction of the thickness of the coating ( 20 ) or parallel to the coating. Coating ( 20 ) according to one of the preceding claims, in which the matrix material ( 28 ) is originally present as a powder, which with the hard material particles ( 30 ) is mixed. Coating ( 20 ) according to claim 9 when referred to any one of claims 2 to 7, wherein the powder ( 28 ) of the matrix material and the hard material particles ( 30 ) into the lot ( 23 ) are embedded. Shovel ( 10 ) for a turbomachine, with a coating ( 20 ) according to one of the preceding claims on the blade tip. Method for coating the blade tip ( 10 ) of a blade for a turbomachine, with the steps of applying ( 103 ; 104 ) of a matrix material ( 28 ) and of coated hard material particles ( 30 ) containing at least cubic boron nitride or silicon nitride or silicon aluminum oxynitride; integral connection ( 106 . 107 . 108 ) of the matrix material ( 28 ) and the hard material particles ( 30 ) with the blade tip ( 10 ) by locally heating the blade tip ( 10 ). Process according to Claim 12, in which the material-bonding connection is a melting ( 105 ) of a solder, a wetting ( 106 ) at least the blade tip ( 10 ) and the matrix material ( 28 ) through the Lot ( 23 ) and a freezing ( 108 ) of the lot ( 23 ). A method according to claim 12 or 13, wherein the applying comprises applying a tape or sheet to the matrix material ( 28 ) and the hard material particles ( 30 ). The method of claim 14 when dependent on claim 13, wherein the concentrations of the matrix material ( 28 ), the hard material particles ( 30 ) and lots ( 23 ) vary continuously over the thickness of the tape or film. The method of claim 13 or claim 14 when referred to claim 13, wherein applying comprises applying a layered structure to a first layer (16). 22 ), a second layer ( 34 ) and a third layer ( 26 ), wherein the first layer ( 22 ) the lot ( 23 ), the second layer ( 34 ) the hard material particles ( 30 ), and wherein the third layer ( 26 ) between the first layer ( 22 ) and the second layer ( 34 ) is arranged. Method according to one of Claims 12 to 16, in which a coating ( 20 ) is applied according to one of claims 1 to 10.

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