Layer with integrated abrasive particles

Abstract

The invention relates to a layer for arranging on a substrate, comprising a matrix layer with a matrix made of an oxidic material. The invention is characterized in that the matrix layer consisting of the matrix made of an oxidic material comprises different oxide particles which cannot be identified as droplets produced as part of a cathodic arc deposition.

Description

[0001] LAYER WITH INCORPORATED ABRASIVE PARTICLES

[0002] The present invention relates to coatings for reducing component wear, which are used, for example, against abradable coatings in wide temperature ranges. Such abradable coatings are applied, for example, to the inside of the casing of a gas turbine, typically using a spraying technology. As the turbine blade rotates, the end of the turbine blade (tip, shroud) comes into contact with the abradable coating and cuts a profile into it through abrasion. This highly precise cut enables the necessary high compression of the gases, which is required for high turbine efficiency.

[0003] Higher gas temperatures are another trend in the further development of gas turbines toward improved efficiency. This trend, in turn, influences the material of the abradable layers, meaning their mechanical stability must be guaranteed at higher temperatures. Abradable layers made of high-temperature-stable materials that are oxidic in nature or contain oxides (such as a developed abradable material or abrasion-resistant material made of Al-Mg spinel) are particularly suitable. The development of abradable layers with greater mechanical stability at high temperatures therefore also requires an improvement in the material at the tip of the turbine blade, which is needed for the cut into the abradable material.

[0004] State of the art

[0005] An example from the prior art is disclosed in US 9957629 B2. On the tip of a turbine blade made of a superalloy, an MCrAlY layer is deposited by electroplating, and abrasive particles of cubic boron nitride (cBN), aluminum oxide, silicon carbide, or other nitrides, oxides, or carbides are embedded in this layer. This layer exhibits higher compressive stresses than conventional MCrAlY layers, which are achieved through a suitable composition of the MCrAlY layer. The compressive stresses firmly embed the abrasive particles in the layer. At the same time, this MCrAlY layer exhibits comparable oxidation resistance to standard MCrAlY, as demonstrated by results in cyclic temperature tests at 1133°C. This is the case even though the abrasive particles are embedded in this layer.

[0006] However, the proposed solution is limited in two respects. First, cBN is not oxidation-resistant, which leads to oxidation at the particle surface. This oxidative wear leads to a decrease in the adhesion of the cBN particles in the MCrAlY coating.

[0007] The second limitation of the proposed solution is the temperature stability of the MCrAlY matrix. At temperatures approaching 1200°C and beyond, the mechanical strength decreases noticeably, resulting in softening of the MCrAlY matrix and, as a result, a loss of the abrasive cBN particles, and the coating system loses its ability to cut into the running-in layer.

[0008] Another patent (EP1743958B1) proposes counteracting the problem of oxidative wear associated with abrasive cBN particles with self-healing coatings. SiC particles are coated on the blade tip prior to incorporation into the coating. Again, an MCrAlY material is preferred for the blade tip coating.

[0009] However, this invention does not solve the problem of reduced mechanical strength of MCrAlY at high temperatures.

[0010] Object of the invention

[0011] It is therefore the object of the present invention to at least partially remedy the aforementioned disadvantages of known layers for arrangement on a substrate and methods for their production. In particular, the object of the invention is to provide a layer for arrangement on a substrate which has low wear, in particular high oxidation resistance, even at high temperatures of, for example, > 1200 °C. The above object is achieved by a layer for arrangement on a substrate according to claim 1 and a method for producing such a layer according to claim 10. Further features and details of the invention can be found in the respective subclaims, the description, and the drawings.In this case, features and details which are described in connection with the layer according to the invention for arrangement on a substrate naturally also apply in connection with the method according to the invention and vice versa, so that with regard to the disclosure of the individual aspects of the invention, reference is or can always be made mutually.

[0012] General description

[0013] Here, the layer according to the invention for arrangement on a substrate comprises a matrix layer with a matrix of oxidic material, wherein the matrix layer comprises oxide particles that can be distinguished from the matrix and that cannot be identified as droplets formed during cathodic arc evaporation.

[0014] The layer according to the invention for arrangement on a substrate can thus comprise a carrier layer (matrix layer) made of an oxide material, wherein the carrier layer (matrix layer) can additionally comprise oxide particles that are distinguishable from the oxide material and are not droplets that have been or can be formed during cathodic arc evaporation. The carrier layer (matrix layer) can preferably be arranged on the substrate.

[0015] The matrix layer can be designed to be oxidation-resistant and preferably contain intermetallic compounds and / or oxide components and / or abrasive particles.

[0016] With a view to simple and effective adaptation of the properties of the respective layer, it can advantageously be provided that the surface of the substrate has centers of nucleation aids. Nucleation aids can be understood, for example, as substances or materials that support the nucleation process, i.e., the formation of small, stable nuclei or crystals in a material. This process is crucial for various physical and chemical processes, such as crystallization, crystal growth, and the formation of phases in materials.

[0017] To ensure thermal shielding or a thermal barrier, the layer may further be porous (having a plurality of pores). The layer may preferably be porous to such an extent that the thermal conductivity is reduced by at least 20%, preferably by at least 50%, compared to a layer without pores.

[0018] To improve adhesion, it may also be advantageous to provide an intermediate layer between the substrate and the matrix layer, wherein the intermediate layer is preferably formed from materials whose melting point is above the melting point of an MCrAIY layer.

[0019] Furthermore, it is conceivable that a further intermediate layer comprising MCrAlY, preferably made of MCrAlY, is provided.

[0020] Advantageously, the layer may comprise an intermediate layer comprising a metallic matrix of intermetallic compounds that are elementally related to abrasive particles to be incorporated and are preferably in the same group of the periodic table of elements.

[0021] Furthermore, in order to increase the abrasion capacity, it can advantageously be provided that the layer comprises additional particles in the form of droplets, wherein the droplets can preferably be produced, in particular have been produced, via cathodic arc evaporation.

[0022] These droplets can advantageously have a different shape and contain chromium and / or aluminum. The invention also further relates to a method for producing a layer for arrangement on a substrate by means of cathodic arc evaporation, preferably a layer described above. According to the method according to the invention, a target with a target material is used as the material source for producing a matrix layer of the layer, wherein particles are embedded in the target material (preferably with a size of 0.01 to 100 pm), which are at least partially transported to the substrate during coating and incorporated there into the matrix layer of the layer.It is understood that the process according to the invention can also be used to produce layers which do not contain oxides and / or contain oxides exclusively in the matrix or in the (abrasive) particles, although the process can advantageously be used to produce layers which contain oxides, preferably not only in the matrix and / or the (abrasive) particles.

[0023] With a view to a simple and controlled introduction of the particles, it can further be provided that the particles have a higher melting point than the target material forming the matrix layer of the layer.

[0024] The target material can contain Cr and / or Al and / or additional abrasive particles.

[0025] Furthermore, the target material can advantageously have an electrical resistance between 0.05 and 3 ohms.

[0026] The process can also advantageously be carried out using a reactive gas, wherein oxygen, in particular exclusively oxygen, is preferably used as the reactive gas.

[0027] The invention also relates to a turbine blade comprising a layer as described above, wherein the layer is applied to a surface of the turbine blade.

[0028] The invention also relates to a tool for machining composite materials and / or borides and / or carbides, comprising a layer as described above, wherein the layer is applied to a surface of the tool.

[0029] The proposed features make it possible to provide a layer for placement on a substrate which:

[0030] • has abrasive particles embedded in the layer with low oxidative wear,

[0031] • its surface is mechanically stable at high temperatures, more temperature-stable than an MCrAlY layer,

[0032] • has grain boundaries to close their interfaces to the abrasive particles during oxidative processes and to lead to a strengthening of the particles incorporated into the layer,

[0033] • has an oxidation-resistant matrix which, in addition to intermetallic compounds, also contains oxidic components or components of the material of the abrasive particles,

[0034] • has an intermediate layer between the substrate and the functional layer, which is designed as an oxidation barrier,

[0035] • has an intermediate layer consisting of a metallic matrix of intermetallic compounds that are element-related (e.g. in the same group of the periodic table of elements) with the abrasive particles to be incorporated.

[0036] It is further described that the layer according to the invention can be produced:

[0037] • by using a target made of a conductive metallic matrix into which abrasive particles are embedded,

[0038] • wherein the target may preferably contain a target material of specific particle size, preferably with an electrical resistance between 0.05 and 3 ohms,

[0039] • via a process of reactive cathodic spark evaporation, whereby a material is synthesized by a reaction between the vapor of the metallic matrix and a reactive gas, which is elementally related to the abrasive particles to be incorporated, • whereby intermetallic compounds with a melting point > 1000°C are produced by the spark path on the target surface.

[0040] The invention can be used, for example, in turbine blades, in such a way that by coating the turbine blade tip with the layer according to the invention, a clean cut is achieved in running-in layers consisting of abradable material.

[0041] Specific description of the invention

[0042] The invention provides a solution to the problems of the prior art described above. The prior art is best described using Figure 1 of patent US9957629B2, in which the abrasive particles (1) are embedded in a metallic matrix (2). This layer system is deposited by the described method on the blade tip (3), i.e., on the tip of the turbine blade, i.e., in the region that cuts into the abradable material on the inside of the turbine casing. The metallic matrix is ​​implemented there as an MCrAlY material, i.e., it is again made of a superalloy like the material of the blade tip, but with a different composition, especially a higher Al content, in order to improve the oxidation resistance of the matrix. However, the mechanical strength of the MCrAlY matrix in the prior art already reaches its limit below a temperature of 1200°C, i.e.,It becomes soft, and the embedded abrasive particles can no longer be held. Furthermore, oxidation begins on the surfaces of the c-BN particles described there at these temperatures, which further contributes to a deterioration in the adhesion of the embedded particles.

[0043] Figure 2 shows, by way of example, on a superalloy substrate (10), the layer (11) according to the invention, which is based on a non-superalloy matrix material (12) which, at temperatures of 1000°C and beyond, has greater mechanical strength than MCrAlY and can have at least partially oxidic character. This layer is deposited by means of a PVD or CVD, preferably a hybrid PVD-CVD process, on the substrate material, for example on a Ni-, Co-, or Ni-Co-based superalloy or a SiC-, C-, or other substrate material, for example on a blade tip. The layer (11) according to the invention has a higher temperature stability than the MCrAlY layer of the prior art.

[0044] However, it may be advantageous to apply a further layer (13) between the superalloy substrate (10) and the layer (11) according to the invention, which allows a better adaptation between the substrate and the layer (11) according to the invention.

[0045] As an example of the layer according to the invention, a layer will be described here which predominantly comprises the elements Al and Cr and which is produced by cathodic spark evaporation of an Al-Cr target in an oxygen-containing atmosphere. The layer also contains oxygen, i.e. portions of the layer comprise Al-Cr-O. This Al-Cr-O is X-ray amorphous after deposition at approx. 500°C using the above-mentioned processes, but becomes increasingly crystalline from around 900°C at annealing temperatures in ambient atmosphere and displays the X-ray reflections of the Al-Cr-O solid solution for the corundum structure. In contrast to MCrAlY, this solid solution structure is stable up to 1400°C and beyond. A thin aluminum oxide layer, also in the corundum structure, forms on its surface during the annealing process.

[0046] The matrix layer (12) of the layer according to the invention is also characterized in the as-deposited state by droplets (spatters) of varying sizes and shapes (14, 15). While spherical droplets (14) have a metallic Cr core with a high chromium content, flat droplets (15) consist predominantly of aluminum with a very low Cr content. These droplets originate in the melting process through the cathodic spark of the affected region of the target. They acquire their characteristic shape during condensation on the substrate surface, which reflects the melting temperature: spherical geometry for a high melting point, flat geometry for a low melting point.The spherical droplets incorporated into the layer during the coating process form grain boundaries (16) when overcoated during the coating process, along which oxygen can diffuse towards the center of the spherical droplet during the subsequent baking process or during application, leading to progressive oxidation of the droplet. This oxidation process is associated with an increase in volume and ultimately leads to stresses in the layer. This is an effect that is entirely desirable in order to clamp hard and advantageously also oxidation-inert foreign bodies (= abrasive particles) (17) in the layer. With increasing oxidation, this stress increases even further. According to the invention, this effect is exploited to firmly anchor abrasive particles (17) in the layer.

[0047] According to the above description, the matrix layer exhibits "self-healing" properties. Firstly, by the formation of an aluminum oxide with a corundum structure on its surface, and secondly, by the closure of the grain boundaries along the spherical droplets due to the volume increase.

[0048] The oxidation-resistant layer (12) serves as a matrix for the incorporation of the abrasive particles (17), for example oxide particles.

[0049] In the example, this matrix (when using an Al-Cr target in the case of spark evaporation) comprises Al-Cr intermetallic compounds such as Al4Cr1, Al9Cr4, AlCr2, but predominantly Al8Cr5 and additionally Al-Cr-O, preferably in a composition that leads to a solid solution with a corundum structure when annealed in the environment. Such a matrix is ​​advantageously produced (as explained below) using the PVD process of reactive cathodic spark evaporation. The oxidation-resistant layer (12) should comprise temperature-stable phases, i.e. phases that have higher melting points than the substrate material to be protected. These can be both intermetallic and oxide phases. These phases can be formed from two elements, as in the example, or can comprise just one element or more than two elements.

[0050] The above example of using Al-Cr as a target material for the formation of intermetallic compounds in the deposited layer and oxides based on the elements of the target material should therefore not be construed as a limitation. Table 1 also lists, by way of example, other target materials, layer phases, and abrasive particles with which coatings according to the invention can be produced for the application discussed here as an example, but also for corresponding applications in other areas where temperature-stable coatings with abrasive particles are required. Such a temperature-stable coating according to the invention with embedded abrasive particles is also referred to below as a functional layer. This table serves only as an example and is not to be considered exhaustive.

[0051] Figure 3 provides a more detailed look at the area between the superalloy substrate (20) and the functional layer (21), the optional intermediate layer (22). This intermediate layer (22) is responsible for the good adhesion of the functional layer (21) to the superalloy substrate (20). It must guarantee good adhesion over a wide temperature range, i.e., it must suppress undesirable diffusion processes that could weaken the adhesion and exhibit sufficient flexibility in adapting to different temperature-induced expansion coefficients.

[0052] For the stability of the inventive layer system, which is discussed in more detail here, it is beneficial that the superalloy substrate surface is not exposed to oxygen, especially activated oxygen, during layer deposition, thus avoiding the formation of mechanically unstable oxides (such as nickel oxide) and oxygen-driven diffusion processes. To achieve this, the superalloy substrate surface must not be exposed to a reactive oxygen plasma, nor must oxygen diffusion to the superalloy substrate interface occur during layer deposition or subsequent layer application.

[0053] This allows us to formulate two advantageous conditions for the construction of the intermediate layer. First, no oxide may be deposited at the transition between the superalloy substrate surface and the intermediate layer (22). Second, the intermediate layer should form or form a good barrier against oxygen, either through the deposition of a subsequent layer or through effects during the specific application.

[0054] This is achieved (to remain with this exemplary layer system) by depositing intermetallic compounds of Al-Cr in the intermediate layer in a first step, preferably and predominantly Al8Cr5 or AlCr2. These intermetallic compounds have a higher melting point than, for example, the MCrAlY material and, when exposed to a reactive oxygen atmosphere, they form an Al-Cr-0 solid solution with a corundum structure, i.e., an oxidation barrier layer and consequently a stable transition to the functional layer (21).

[0055] As shown schematically in Figure 4, the intermediate layer (30) on the substrate (31) can also be designed as a multilayer coating before the actual functional layer (32) is deposited. After a sufficiently thick intermetallic layer (33) made of Al-Cr is deposited in a first step, which serves as an oxygen barrier layer, a further layer based on this material (34) is deposited with moderate oxygen addition, which is then interrupted again and so on until an intermediate layer as a multilayer coating (30) is created made of Al-Cr / Al-Cr-0 material, whereby the oxygen content in the Al-Cr-0 layer can be of varying magnitude. This multilayer coating approach will also be discussed further below when it comes to explaining the incorporation of the abrasive particles (35) into the functional layer.

[0056] The requirements for the functional layer are primarily oxidation resistance and mechanical strength for the respective application, as well as the ability to firmly incorporate abrasive particles. In the case of blade tip applications, the functional layer must be stable in the temperature range around 1100°C and beyond. The process for producing the abrasive functional layer will be discussed in more detail below.

[0057] The preferred methods for incorporating abrasive particles into a layer are based on evaporation using solid-state sources in a vacuum environment. Electron beam evaporation of material, such as an ingot, from a crucible is well known. If particles are deliberately incorporated into the ingot during the ingot manufacturing process, they are entrained by the evaporated material and can be incorporated into the deposited layer. However, experiments have shown that without further measures, the incorporation of the abrasive particles into the layer is insufficient. This may be due in part to the low kinetic energies of the particles and in part to the insufficient anchoring of the particles in the matrix layer.

[0058] One aim of the invention was therefore to increase the kinetic energy of the abrasive particles during evaporation of the matrix material (ingot) and to improve their anchoring in the growing layer.

[0059] Therefore, cathodic spark evaporation (CAE) was investigated. In contrast to the aforementioned process, the target to be evaporated in CAE must be conductive. To use the example, the target consists of Al and Cr and has, for example, a composition expressed in atomic percent of Al70Cr30. Additionally, abrasive particles were added to the target during the manufacturing process.

[0060] These manufacturing processes for target production can include forging processes, melting processes, sintering processes, hot isostatic pressing processes, or spark plasma sintering processes. However, the targets can also be produced using other manufacturing processes, for example, by simultaneously spraying a metallic material and an oxide material onto a base plate using a process such as APS, HVOF, or LPPS.

[0061] The targets produced in this way are described schematically in Figure 5. The targets (40) comprise a metallically conductive matrix (41) into which the abrasive particles (42) have been embedded. For reasons of stability, such a target can, as is known to those skilled in the art, be applied to a backing plate (43) if it cannot be manufactured in one piece. In most cases, abrasive particles that are insulating are used, for example corundum, quartz, silicates, diamond, cubic boron nitride and other nitrides, to name just a few. Particles made of poorly (semi-)conductive materials such as silicon carbide or boron carbide or other carbides or borides are also suitable as abrasive particles due to their high hardness. However, hard metals can also be incorporated into the target.The quantity and size of the abrasive particles (42) introduced into the metallic matrix (41) depend on the specific application of the layer to be synthesized and are usually subject to an optimization process. This is similar, for example, to abrasives applications, where the size of the particles in the abrasive is matched to the desired roughness of the substrate surface to be ground. Since both the metallic matrix (41) and the particles (42) can be made of different materials with different densities and different chemical compositions, a concentration of abrasive particles to metallic matrix in the target cannot be specified.

[0062] When designing the target, however, care must be taken to ensure that the abrasive particles only influence the conductivity of the target matrix to the extent that RCAE can be performed. This is measured by specifying the resulting resistance (impedance) of the cathodic spark discharge using such a target, which is provided with the corresponding abrasive particles. This resistance ranges from 0.05 to approximately 3 ohms. Those skilled in the art are, of course, aware that this resistance is not only due to the incorporation of insulating particles into the otherwise conductive target, but that other parameters of the spark discharge, such as the anode area, the magnetic field at the target, or the reactive gas, also influence the discharge voltage.

[0063] The particle size is shown schematically in Figure 6. This figure shows two typical particle cross-section shapes (50, 51 ), and their largest cross-sectional dimensions (D1, D2) are used to indicate the particle size. Both spherical and sharp-edged particles can be used for specific applications. Commercially available powders in sizes between 50 nm and 10 pm can be advantageously used; for special applications, particles around 10 nm and up to 100 pm can also be embedded into the target.

[0064] The targets described above with the incorporated abrasive particles are, as already mentioned, used as cathodes for RCAE. Excellent results have been achieved using this method for incorporating the abrasive particles. This is due to the fact that this evaporation method generates numerous spark spots on the target surface, which melt small areas of the target surface extremely briefly and explosively vaporize the target matrix material. If a particle is located in this area, it is entrained and receives sufficient energy to reach the coating surface with the vaporized material. The choice of abrasive particles can be selected according to the coating application. In the example, the abrading process of the turbine blade is described in the abrading material, and corundum particles have been incorporated into the target.These particles retain their chemical composition during the evaporation of the target material and during incorporation into the layer during deposition. The reason for this is that the abrasive particles have a higher melting point than the phases formed on the target surface during spark evaporation. This is a design criterion for an application that requires an abrasive effect.

[0065] Two additional reasons are important for the permanent incorporation of the abrasive particles into the growing layer. First, RCAE allows a target design in which the metallic matrix can be selected so that it contains elements that are also found in the abrasive particles. For example, a target made of Al (Al matrix) with Al2O3 particles incorporated, or a target made of an Al-Cr matrix with Al2O3 particles incorporated. Or a Zr matrix with ZrO2 particles or YSZ particles incorporated, or a Zr-Y matrix with YSZ particles incorporated.

[0066] Such matrices are particularly advantageous when, during RCAE, a layer can be synthesized by adding a reactive gas to the CAE, in this case oxygen, whose properties are close to those of the abrasive particles, for example with regard to the thermal expansion coefficient. To return to the example of the Al-Cr target with the embedded Al2O3 particles, the RCAE method can in this case be used to synthesize Al-Cr-O, which, as a solid solution, has lattice constants similar to Al2O3 in a corundum structure. In other words, for the embedding of the abrasive particles, it is particularly advantageous to select the conductive matrix during target design such that a layer is synthesized in a reactive process that results in a material that is similar to the material of the abrasive particles.This applies particularly to the synthesis of oxides with oxide particle incorporation, but also applies analogously to nitrides and carbides and their mixtures, for example to a Ti target into which TiC particles are incorporated and in which C2H2 is added as a reactive gas during the evaporation process.

[0067] The second reason why RCAE is particularly suitable for incorporating abrasive particles embedded in the target into the layer to be synthesized is the ability to vary the reactive gas during the reactive evaporation of the target, thus producing a layer with a multilayer structure consisting of layers that react with the reactive gas to varying degrees. As an example, consider again an Al-Cr target with abrasive particles of aluminum oxide (corundum) that is evaporated in an oxygen reactive gas.In order to achieve a multilayer coating, the oxygen flow is varied in such a way that at higher oxygen flow, a complete oxidation of the Al-Cr to (Al,Cr)2O3 occurs, i.e. a stoichiometric ternary oxide is produced, but at lower oxygen flow, a substoichiometry with regard to the oxygen is established, which leads to at least a two-phase layer of oxide and metallic components.

[0068] If such a layer is exposed to higher temperatures during application in the atmosphere, oxygen diffuses along the grain boundaries and causes oxidation along these regions in the layer where complete oxidation had not occurred due to insufficient oxygen flow during layer synthesis. This, in turn, leads to an increase in volume in these areas, to compressive stresses, and ultimately to better anchoring of the abrasive particles in the layer. Experience shows particularly good particle incorporation into the multilayer coating if the particle dimensions (D1, D2 in Figure 6) are approximately the same size as the individual layer thickness.

[0069] Figure 7 shows such a multilayer coating with particle incorporation. Using a dome grinding process, the multilayer coating was ground down to the underlying substrate and measured. The coating has a total thickness of approximately 4.2 pm and consists of individual layers of approximately 220 nm Al-Cr-O. x and approx. 320 nm Al-Cr-O y , i.e., composed of individual Al-Cr layers with different oxygen contents. The light microscope image also shows particles (60) of varying sizes embedded in the multilayer structure. After the dome grinding, primarily those particles (60) remain embedded that are approximately the size of the individual layer thickness, while larger particles (61) are removed by the dome grinding.

[0070] Figure 8 shows a cross-sectional scanning electron micrograph of another multilayer with a greater thickness of approximately 13 pm. This image shows the incorporation of abrasive particles that are larger than the individual layer thickness of the multilayer. The image shows particles (70) with sizes between approximately 1 pm and approximately 5 pm.

[0071] Figure 9 documents the scraping results in a swabbing material for two different multilayer coatings. Both coatings, produced according to the above description, show a clean cut into the swabbing material and uniform wear of the coatings on the blade tip at a swabbing temperature of 1200°C.

[0072] In general, this concept can be applied to many different substrates, e.g. superalloy, SiC CMC (composites), C / C composites, Ni-based alloys, steels, or cemented carbides.

Claims

Claims 1. A layer for arrangement on a substrate, comprising a matrix layer with a matrix of oxidic material, characterized in that the matrix layer comprises oxide particles which can be distinguished from the matrix of oxidic material and which cannot be identified as droplets formed during cathodic arc evaporation.

2. Layer for arrangement on a substrate according to claim 1, characterized in that the matrix layer is designed to be oxidation-resistant, wherein the matrix layer preferably comprises intermetallic compounds and / or oxide-containing compounds and / or abrasive particles.

3. Layer for arrangement on a substrate according to claim 1 or 2, characterized in that the surface of the substrate has centers of nucleation aids.

4. A layer for arrangement on a substrate according to any one of the preceding claims, characterized in that the layer has a plurality of pores for reducing thermal conductivity.

5. Layer for arrangement on a substrate according to one of the preceding claims, characterized in that an intermediate layer is provided between the substrate and the matrix layer, wherein the intermediate layer is preferably formed from materials whose melting point is above the melting point of an MCrAlY layer.

6. Layer for arrangement on a substrate according to claim 5, characterized in that a further intermediate layer comprising MCrAlY, preferably consisting of MCrAlY, is provided.

7. Layer for arrangement on a substrate according to one of the preceding claims, characterized in that an intermediate layer is provided which has a metallic matrix of intermetallic compounds which are element-related are to be incorporated with abrasive particles and preferably in the same group of the periodic table of elements.

8. Layer for arrangement on a substrate according to one of the preceding claims, characterized in that the layer comprises additional particles in the form of droplets, wherein the droplets can preferably be produced, in particular have been produced, via cathodic arc evaporation.

9. Layer for arrangement on a substrate according to one of the preceding claims, characterized in that the droplets are at least partially formed in different shapes and sizes and contain chromium and / or aluminum.

10. A method for producing a layer for arrangement on a substrate by means of cathodic arc evaporation, preferably a layer described above, characterized in that a target with a target material is used as the material source for producing a matrix layer of the layer, wherein particles are embedded in the target material which are at least partially transported to the substrate during coating and incorporated there into the matrix layer of the layer.

11. The method according to claim 10, characterized in that the particles have a higher melting point than the target material forming the matrix layer.

12. Method according to claim 10 or 11, characterized in that the target material comprises Cr and / or Al and / or additional abrasive particles.

13. Method according to claim 10 to 12, characterized in that the target material has an electrical resistance between 0.05 and 3 ohms.

14. The method according to claim 10 to 13, characterized in that the method is carried out using a reactive gas, wherein oxygen is preferably used as the reactive gas.

15. A turbine blade comprising a layer according to any one of claims 1 to 9, wherein the layer is applied to a surface of the turbine blade.

16. A tool for machining composite materials and / or borides and / or carbides, comprising a layer according to any one of claims 1 to 9, wherein the layer is applied to a surface of the tool.

Images