METHOD FOR PRODUCING A COATING, AND COATING

Abstract

The invention relates to a method for producing a coating in which: a substrate is provided; and the substrate is provided with a coating, in particular by means of atmospheric plasma spraying, with a plasma torch having a torch nozzle being used, by means of which torch a plasma jet is generated from a supplied process gas, and with a supplied spraying material being applied to the substrate by means of the plasma jet in order to obtain the coating, wherein the torch nozzle is characterized by a nozzle diameter or a minimum nozzle diameter in the range of 4 mm to 8 mm, in particular 5 mm to 8 mm, preferably 5 mm to 7 mm, and wherein the process gas stream is at least 40 slpm. The invention further relates to a component comprising a substrate and a coating.

Claims

1. A method for producing a coating (12) in which a substrate (1) is provided, the substrate (1) is provided with a coating (12) by, in particular, atmospheric plasma spraying, wherein a plasma torch (2) with a torch nozzle (3) is used, with which a plasma jet (4) is generated from a supplied process gas (10), and wherein a supplied spraying material (5) is applied to the substrate (1) with the plasma jet (4) in order to obtain the coating (12), wherein the torch nozzle (3) is characterized by a nozzle diameter (D) or a minimum nozzle diameter (D) in the range from 4 mm to 8 mm, in particular 5 mm to 8 mm, preferably 5 mm to 7 mm, and in that the process gas flow is at least 40 slpm.

2. Method according to claim 1, wherein the process gas flow is at least 50 slpm, in particular at least 60 slpm, preferably at least 70 slpm, particularly preferably at least 100 slpm, very particularly preferably at least 150 slpm.

3. Method according to claim 1, wherein a single-layer or multilayer coating (12) is produced, and/or wherein a particularly semicrystalline silicon or silicate or aluminate layer, hafnate layer or perovskite layer or mixtures thereof is produced as the coating (12) or as part of the coating (12).

4. Method according to claim 1, wherein a spray material (5) is used which comprises or is given by at least one rare earth silicate, preferably Yb2Si2O7, and/or that a spray material (5) is used which comprises or is given by at least one rare earth aluminate, preferably Y3Al5O12 and/or YAlO3 and/or LaM-gAl11O19.

5. Method according to claim 1, wherein a spray material (5) is used which comprises or is given by at least one rare earth hexaaluminate, in particular LaMgAl11O19.

6. Method according to claim 1, wherein a spray material (5) with a mean particle diameter of at most 80 micrometers, in particular at most 50 micrometers, preferably at most 40 micrometers, particularly preferably at most 30 micrometers, is used.

7. Method according to claim 1, wherein a spray material (5) with a mean particle diameter of less than 30 micrometers is used, in particular a spray material (5) with a mean particle diameter in the range from 15 micrometers to 29 micrometers, preferably 10 micrometers to 29 micrometers, particularly preferably 15 micrometers to 29 micrometers.

8. Method according to claim 1, wherein the spray distance (Ds) between the torch nozzle (3) and the substrate (1) is in the range from 60 mm to 200 mm, in particular 70 mm to 180 mm, preferably 80 mm to 140 mm, particularly preferably 100 mm or 120 mm.

9. Method according to claim 1, wherein the current is in the range from 300 A to 550 A, in particular in the range from 300 A to 400 A or 400 A to 500 A, preferably amounts to 375 A or 450 A or 470 A.

10. Method according to claim 1, wherein the burner speed is at most 2000 mm/s, in particular in the range from 100 mm/s to 1500 mm/s, preferably from 200 mm/s to 600 mm/s, especially preferably amounts to 500 mm/s.

11. Method according to claim 1, wherein the feed rate of the spray material (5) is at least 5 g/min, in particular at least 10 g/min, preferably amounts to 10 g/min or 30 g/min or 90 g/min.

12. Method according to claim 1, wherein the substrate (1) is preheated at least in sections to a temperature of at least 200° C. before the application of the coating (12), and/or wherein the substrate (1) is heated at least in sections to a temperature of at least 250° C., preferably at least 300° C., during the application of the coating (12).

13. Method according to claim 1, wherein the substrate (1) comprises silicon, in particular silicon carbide and/or silicon nitride, and/or wherein the substrate (1) comprises nickel, in particular a nickel-based superalloy, and/or the substrate (1) comprises alumina-based composites.

14. Method according to claim 1, wherein the coating (12) is produced in a single pass, preferably wherein a feed rate of the spray material (5) of at least 50 g/min is set.

15. Method according to claim 1, wherein the process gas flow is at least 100 slpm, preferably in the range from 100 slpm to 500 slpm, particularly preferably in the range from 100 slpm to 400 slpm, wherein the torch nozzle (3) is characterized by a nozzle diameter (D) or a minimum nozzle diameter (D) in the range from 5 mm to 8 mm, preferably 5 mm to 7 mm, particularly preferably 6 to 7 mm, and wherein a spray material (5) with a mean particle diameter of at most 40 micrometers is used, in particular a spray material with a mean particle diameter in the range from 5 micrometers to 40 micrometers, preferably in the range from 10 micrometers to 40 micrometers, particularly preferably in the range from 15 micrometers to 40 micrometers, and wherein the substrate (1) is heated, at least in sections, to a temperature of at least 300° C. during the application of the coating (12), in particular to a temperature in the range from 300° C. to 700° C., preferably in the range from 300° C. to 500° C.

16. Method according to claim 15, wherein the spray distance (Ds) between the torch nozzle (3) and the substrate (1) is at least 100 mm, preferably in the range from 100 mm to 200 mm, and that the current is at least 400 A, preferably in the range from 400 A to 550 A.

17. Component comprising a substrate (1) and a coating (12) obtained by carrying out the method according to claim 1.

18. Method according to claim 2, wherein a single-layer or multilayer coating (12) is produced, and/or wherein a particularly semicrystalline silicon or silicate or aluminate layer, hafnate layer or perovskite layer or mixtures thereof is produced as the coating (12) or as part of the coating (12).

19. Method according to claim 2, wherein a spray material (5) is used which comprises or is given by at least one rare earth silicate, preferably Yb2Si2O7, and/or that a spray material (5) is used which comprises or is given by at least one rare earth aluminate, preferably Y3Al5O12 and/or YAlO3 and/or LaM-gAl11O19.

20. Method according to claim 3, wherein a spray material (5) is used which comprises or is given by at least one rare earth silicate, preferably Yb2Si2O7, and/or that a spray material (5) is used which comprises or is given by at least one rare earth aluminate, preferably Y3Al5O12 and/or YAlO3 and/or LaM-gAl11O19.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0067] The drawings show:

[0068] FIG. 1 a purely schematic block diagram showing the steps of five embodiments of the method according to the invention;

[0069] FIG. 2 is a purely schematic, highly simplified sectional view of a plasma torch with torch nozzle, which is used within the scope of the embodiments with the steps according to FIG. 1;

[0070] FIG. 3 a micrograph of a coating obtained according to a first embodiment of the method according to the invention;

[0071] FIG. 4 an X-ray diffraction pattern of the coating according to FIG. 3;

[0072] FIG. 5 a micrograph of a coating obtained with a nozzle diameter of 9 mm;

[0073] FIG. 6 X-ray diffraction pattern of the coating according to FIG. 5;

[0074] FIG. 7 a micrograph of a coating obtained according to a second embodiment of the method according to the invention;

[0075] FIG. 8 an X-ray diffraction pattern of the coating according to FIG. 7;

[0076] FIG. 9 a micrograph of a coating obtained according to a third embodiment of the method according to the invention;

[0077] FIG. 10 an X-ray diffraction pattern of the coating according to FIG. 9;

[0078] FIG. 11 a micrograph of a coating obtained according to a fourth embodiment of the method according to the invention;

[0079] FIG. 12 an X-ray diffraction pattern of the coating according to FIG. 11;

[0080] FIG. 13 a micrograph of a coating obtained according to a fourth embodiment of the method according to the invention; and

[0081] FIG. 14 an X-ray diffraction pattern associated with the coating according to FIG. 13.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

[0082] In the following, five embodiments of the method for producing a coating according to the invention are described.

[0083] In all examples, a substrate 1 is provided in a first step S1 (cf. FIG. 1). In the first to fourth exemplary embodiments, the substrate 1 is a substrate 1 with silicon, specifically a substrate 1 made of a fiber composite material with a silicon bonding agent layer (bondcoat), on which the coating is produced in each case. In the fifth exemplary embodiment , on the other hand, a substrate made of a nickel-based material is provided in step S1, in particular a substrate 1 made of a nickel-based superalloy. The substrate 1 is only visible in the purely schematic, highly simplified FIG. 2.

[0084] In a step S2, the substrate 1 is preheated in each case.

[0085] In a step S3, the substrate 1 is coated in each case by atmospheric plasma spraying (APS). A plasma torch 2 (cf. FIG. 2) with a torch nozzle 3 is used for plasma generation in a manner known per se, with which a plasma jet 4 is generated from a supplied process gas, into which a spray material 5 in powder form is injected.

[0086] The plasma torch 2 has a housing 6 in which a cathode 7 and at least one anode 8 are arranged, which are spaced apart to form a narrow gap. In the examples described here, the plasma torch 2 has three anodes 8. In all five embodiment examples, this is the TriplexPro-210 model from Oerlikon Metco, whereby this is to be understood purely as an example.

[0087] An arc is generated between the electrodes 7, 8 by high-frequency ignition. During operation, a process gas 10 flows between the electrodes 7, 8, which is indicated in simplified form by arrows in FIG. 2, and a gas discharge 9 takes place. With an appropriately selected process gas supply, the plasma jet 4 is formed, which emerges from the nozzle 3 of the plasma torch 2 bundled and at high velocity. The powdered spray material 5 is injected into the plasma jet 4 from the side, via the spray material feeds 11 oriented orthogonally to the plasma jet 4. It should be noted that the orthogonal spray material feed is to be understood as an example. The powder feed is additionally indicated by arrows in FIG. 2. Due to the high plasma temperatures, the powdered spray material 5 is melted, carried along with the plasma jet 4, and thrown onto the substrate 1 to be coated. As a result, a coating 12 is obtained (step S3).

[0088] It should be noted that suitable means 13 are provided for the process gas supply, which are indicated by arrows in the purely schematic FIG. 2. In the described example, these comprise at least one compressed gas cylinder and a mass flow controller.

[0089] As can be seen, the torch nozzle 3 forms the final area, in other words the end area of the plasma torch 2, from which the plasma jet 4 emerges during operation and which is correspondingly turned towards the substrate 12 to be coated or is turned towards during operation. The nozzle 3 can be formed by the anode 8 of the plasma torch 2 or, in the case of several anodes 8, by the anodes 8 of the plasma torch 2 or a section thereof, in particular on the outlet side. The nozzle 3 can also be a separate element from the anode(s) 8, which is arranged (directly) downstream of the anodes. This is the case in the example shown in FIG. 2. The nozzle 3 is given here by an annular element defining a flow channel 14. The flow channel 14 defined by the nozzle 3 forms the outlet end section 14 of the torch flow channel 15 defined by the plasma torch 2 as a whole.

[0090] In accordance with the invention, the torch nozzle 3 is characterized by a nozzle diameter D in the range from 4 mm to 8 mm, in particular 5 mm to 8 mm, preferably 5 mm to 7 mm. In all four examples, the nozzle diameter D of the burner nozzle 3 is 6.5 mm. The nozzle diameter D is, as can be seen, the diameter of the flow channel 14 defined by the nozzle 3. It should be noted that the nozzle 3 defines a cylindrical flow channel 14 and thus has an internal diameter D which remains constant over its entire extent in the gas/plasma flow direction. The nozzle diameter D is therefore 6.5 mm everywhere. This is not necessarily the case. Alternatively, nozzles with a variable nozzle diameter can also be used. In this case, the minimum nozzle diameter lies within the ranges mentioned.

[0091] In all embodiments, a process gas flow of at least 40 slpm is also set in accordance with the invention.

[0092] The process parameters selected in each of the five embodiment examples and the layers 12 produced are discussed in more detail below.

[0093] Example 1:

[0094] According to exemplary embodiment 1, a protective coating 12 with low crack density and increased crystallinity is produced.

[0095] The spray material 5 used is a rare earth silicate, here Yb2Si2O7, in powder form. It is also possible, for example, to use a spray material 5 comprising at least one rare earth hexaaluminate, in particular LaMgAl11O19, or provided thereby. A preferred method of producing the powder 5, which has been used in the present case, is agglomerated and sintered. The powder 5 has an average particle diameter of below 50 micrometers, below 30 micrometers has proven to be particularly suitable. In the present case, this is 20 micrometers.

[0096] Furthermore, a spraying distance Ds (cf. FIG. 2) in the range of 70 mm to 180 mm is selected, in this case 100 mm.

[0097] The process gas flow is set to a total flow of at least 40 slpm, in particular at least 50 slpm. In the present case, 50 slpm is selected. Argon is used as the process gas 10 in this example.

[0098] The current is in the range from 300 A to 400 A, and amounts to 375 A in this example.

[0099] The torch speed is selected to be a maximum of 2000 mm/s, and amounts to 500 mm/s in this example.

[0100] The feed rate of the spray material 5 is selected to be at least 10 g/min, is specifically 30 g/min here.

[0101] During preheating in step S2, the substrate 1 is brought to a temperature of at least 200° C., in this case to approx. 300° C.

[0102] During the actual coating process in step S3, the substrate 1 is heated to at least 250° C., in the exemplary embodiment described here to approx. 270° C.

[0103] FIG. 3 shows a micrograph of the resulting coating 12 of Yb2Si2O7 produced on the substrate 1 given by a fiber composite with the silicon bondcoat. The coating has a homogeneous microstructure with high density and very fine pores. Only short, unconnected cracks occur. An X-ray diffractogram measurement (XRD measurement, cf. FIG. 4) shows an increased degree of crystallinity of 10% after a Rietveld redefinition. The degree of crystallinity is abbreviated as crys in the figures. In this and all other X-ray diffractograms, the 2Theta angle is plotted on the X-axis and the intensity, specifically the root of the counts, is plotted on the Y-axis. The 2Theta angle is, in a known way, the angle at which the intensity of the diffracted X-rays is measured with respect to the angle of incidence (in Bragg arrangement angle of incidence=angle of reflection).

[0104] For comparison, FIG. 5 shows the microstructure of a coating with a coarse crack produced by means of APS and a nozzle diameter of 9 mm, also in a micrograph. FIG. 6 shows a corresponding X-ray diffractogram with a recognizable predominantly amorphous component. Here, the current was 450 A, the process gas flow 50 slpm argon, the spray distance Ds 80 mm and the torch speed 500 mm/s.

[0105] Example 2:

[0106] According to the second embodiment, a protective coating 12 with high crystallinity and particularly low foreign phase content is produced.

[0107] The spray material 5 used is a rare earth silicate, Yb2Si2O7, in powder form. For example, a spray material 5 can also be used which comprises at least one rare earth hexaaluminate, in particular LaMgAl11O19, or is provided thereby. A preferred method of producing the powder 5, which has been used in the present case, is agglomerated and sintered. The powder 5 has an average particle diameter of below 50 micrometers, below 40 micrometers has proven to be particularly suitable. In the present case, this is 30 micrometers.

[0108] A spraying distance Ds in the range from 70 mm to 180 mm is also selected, in this case 120 mm.

[0109] The process gas flow is set to a total flow of at least 80 slpm, in particular at least 100 slpm. In the present case, 110 slpm is selected. Argon is used as the process gas 10.

[0110] The current is in the range from 400 A to 500 A, and amounts to 450 A in the present case.

[0111] The burner speed is set to a maximum of 2000 mm/s, in this case 500 mm/s.

[0112] The feed rate of the spray material 5 is selected to be at least 10 g/min, is specifically 30 g/min here.

[0113] During preheating in step S2, the substrate 1 is brought to a temperature of at least 200° C., in this case to approx. 300° C.

[0114] During the actual coating process in step S3, the substrate 1 is heated to at least 300° C., in the embodiment example described here to about 400° C.

[0115] A special feature of this example is that this layer 12 can be produced with a particularly low proportion of secondary phase Yb2Si2O7.

[0116] FIG. 7 shows the resulting coating of Yb2Si2O7 produced on the substrate 1 given by a fiber composite with the silicon bondcoat. The coating has a homogeneous microstructure with high density and very fine pores. Only short, unconnected cracks occur. An XRD measurement (cf. FIG. 8) shows an increased degree of crystallinity of 92% after a Rietveld redefinition. As crystalline-line phases 98% Yb2Si2O7 and 2% Yb2SiO5 were determined.

[0117] Example 3:

[0118] According to the third embodiment, a protective coating 12 with low porosity is prepared from a mixture of fine Yb silicate powders.

[0119] A mixture of rare earth silicates, preferably SE disilicates and monosilicates in powder form, is used as the spray material 5. Preferably, a mixture of Yb2Si2O7 and Yb2SiO5 is used. Here, a mixture of 75% Yb2Si2O7 and 25% Yb2SiO5 is used, although this is to be understood as exemplary. For example, a spray material 5 can also be used which comprises or is given by at least one rare earth hexaaluminate, in particular LaMgAl11O19.

[0120] The powder 5 has an average particle diameter of below 50 micrometers, below 30 micrometers has proven to be particularly suitable. Presently, this is 20 micrometers. A preferred method of producing the powder 5 is agglomeration and sintering.

[0121] Furthermore, an injection distance Ds in the range from 70 mm to 180 mm is selected, in this case 120 mm.

[0122] The process gas flow is set to a total flow of at least 80 slpm, in particular at least 100 slpm. In the present case, 110 slpm is selected. Argon is used as the process gas 10.

[0123] The current is in the range from 400 A to 500 A, and amounts to 450 A in the present case.

[0124] The burner speed is set to a maximum of 2000 mm/s, in this case 500 mm/s.

[0125] The feed rate of the spray material 5 is selected to be at least 10 g/min, is specifically 30 g/min here.

[0126] During preheating in step S2, the substrate 1 is brought to a temperature of at least 200° C., in this case to approx. 300° C.

[0127] During the actual coating process in step S3, the substrate 1 is heated to at least 300° C., in the embodiment example described here to about 500° C.

[0128] A special feature of this example is that a coating 12 with a particularly low porosity can be produced.

[0129] FIG. 9 shows the resulting coating 12 of 75% Yb2Si2O7 and 25% Yb2SiO5 produced on the substrate 1 given by a fiber composite with the silicon bondcoat. The coating 12 has a homogeneous microstructure with high density and low porosity. Only short, unconnected cracks as well as isolated coarse pores appear. An XRD measurement (cf. FIG. 10) shows a degree of crystallinity of 96% after a Rietveld redefinition. As crystalline phases 75% Yb2Si2O7 and 25% Yb2SiO5 were determined.

[0130] Example 4:

[0131] According to Example 4, a comparatively thick protective coating 12 of at least 100 micrometers is produced by means of a single coating pass.

[0132] The spray material 5 used is a rare earth silicate, Yb2Si2O7, in powder form. For example, a spray material 5 can also be used which comprises at least one rare earth hexaaluminate, in particular LaMgAl11O19, or is given by this. The powder 5 has an average particle diameter of less than 50 micrometers, less than 40 micrometers has proven to be particularly suitable. In the present case, this is 30 micrometers. A preferred method of producing the powder 5 is agglomeration and sintering.

[0133] Furthermore, an injection distance Ds in the range from 80 mm to 140 mm is selected, in this case 120 mm.

[0134] The process gas flow is set to a total flow of at least 100 slpm, in particular at least 150 slpm. In the present case, 174 slpm is selected. A mixture of argon and helium is used as process gas 10. In this case, 170 slpm argon and 4 slpm helium are used.

[0135] The current is in the range from 400 A to 500 A, and amounts to 450 A in the present case.

[0136] The torch speed is selected to a maximum of 500 mm/s, is 250 mm/s in this case.

[0137] The feed rate of the spray material 5 is selected to be at least 50 g/min, is specifically 90 g/min here.

[0138] During preheating in step S2, the substrate 1 is brought to a temperature of at least 200° C., in this case to approx. 300° C. The substrate 1 is heated to a temperature of at least 200° C., in this case to approx. 300° C.

[0139] During the actual coating process in step S3, the substrate 1 is heated to at least 300° C., in the embodiment example described here to approx. 420° C.

[0140] A special feature of this example is that a comparatively thick layer 12 of, for example, 150 micrometers can be produced with a single pass.

[0141] FIG. 11 shows a micrograph of the resulting coating 12 of Yb2Si2O7 produced on the substrate 1 given by a fiber composite with the silicon bondcoat. The coating 12 has a homogeneous microstructure with high density and very fine pores. No cracks occurred. An XRD measurement (cf. FIG. 12) shows a degree of crystallinity of 96% after a Rietveld redefinition. As crystalline phases 95% Yb2Si2O7 and 5% Yb2SiO5 were determined.

[0142] Example 5:

[0143] According to exemplary embodiment 5, a dense crystalline Y3Al5O12 top layer for a TBC system for protecting a substrate 1 made of a nickel-based material, in particular a nickel-based superalloy, is prepared with an MCrAlY bond coat (M=Ni, Co). Accordingly, as noted above, in the fifth exemplary embodiment, a deviating substrate 1 of corresponding embodiment is provided in step S1.

[0144] A further difference is given by the fact that the spray material 5 used is not a rare earth silicate but a rare earth aluminate in powder form, specifically Y3AL5O12 in the example described here. For example, a spray material 5 comprising or given by at least one rare earth hexaaluminate, in particular LaMgAl11O19, can also be used. The powder 5 has an average particle diameter of at most 80 micrometers, at most 30 micrometers has proven to be particularly suitable. In the present case, it is 30 micrometers. A preferred production method of the powder 5 used in the present case is agglomeration and sintering.

[0145] Furthermore, an injection distance Ds in the range from 70 mm to 150 mm is selected, in this case 80 mm.

[0146] The process gas flow is set to a total flow of at least 40 slpm, in particular at least 50 slpm. In the present case, 56 slpm is selected. A mixture of argon and helium is used as process gas 10. 50 slpm argon and 6 slpm helium are used.

[0147] The current is in the range of 350 A to 550 A, and amounts to 470 A in the present case.

[0148] The burner speed is selected to be a maximum of 2000 mm/s, and is 250 mm/s in this case.

[0149] The feed rate of the spray material 5 is selected to be at least 5 g/min, is specifically 10 g/min here.

[0150] During preheating in step S2, the substrate 1 is brought to a temperature of at least 200° C., in this case to approx. 300° C.

[0151] During the actual coating process in step S3, the substrate 1 is heated to at least 300° C., in the embodiment example described here to about 600° C.

[0152] FIG. 13 shows a micrograph of the resulting coating 12 of Y3Al5O12 produced on the substrate 1 from a nickel-based material with a MCrAlY bondcoat (M=Ni,Co). The coating 12 exhibits a homogeneous microstructure with high density and very fine pores. Only short, unconnected cracks occurred. An XRD measurement (cf. FIG. 14) shows a degree of crystallinity of over 60% after Rietveld redefinition.

[0153] It should be noted that the coatings 12 obtained according to all five embodiments of the method according to the invention are examples of coatings 12 according to the invention.