EP4225961A1

EP4225961A1 - Method for producing a coating, and coating

Info

Publication number: EP4225961A1
Application number: EP21769446.2A
Authority: EP
Inventors: Emine BAKAN; Markus Wolf; Georg Mauer; Daniel Emil Mack; Robert Vassen
Original assignee: Forschungszentrum Juelich GmbH
Current assignee: Forschungszentrum Juelich GmbH
Priority date: 2020-10-06
Filing date: 2021-08-31
Publication date: 2023-08-16
Also published as: US20230328870A1; WO2022073697A1; DE102020126082A1

Abstract

The invention relates to a method for producing a coating (12) in which: - a substrate (1) is provided; and - the substrate (1) is provided with a coating (12), in particular by means of atmospheric plasma spraying, with a plasma torch (2) having a torch nozzle (3) being used, by means of which torch a plasma jet (4) is generated from a supplied process gas (10), and with a supplied spraying material (5) being applied to the substrate (1) by means of the plasma jet (4) in order to obtain the coating (12), wherein the torch nozzle (3) is characterised by a nozzle diameter (D) or a minimum nozzle diameter (D) 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 (1) and a coating (12).

Description

DESCRIPTION

Process for producing a coating and coating

The invention relates to a method for producing a coating, in which a substrate is provided, the substrate is provided with a coating, in particular by atmospheric plasma spraying, a plasma torch with a torch nozzle being used, with which a plasma jet is generated from a supplied process gas, and wherein a supplied spray material is applied to the substrate with the plasma jet to obtain the coating.

In principle, it is already known from the prior art to provide materials with so-called thermal and/or environmental insulation layers. The English terms Thermal Barrier Coatings (TBC), Environmental Barrier Coatings (EBC) and Thermal/Environmental Barrier Coatings (T/EBC) are also used for these. The coatings usually consist of ceramic materials. In particular, they have the task of protecting the respective substrate material against temperatures, corrosion and/or oxidation.

For example, substrates made of silicon-containing materials are provided with such layers. Thus, EP 1 142 850 A1 discloses a T/EBC for such. It is described that the coatings can be deposited, in other words deposited, using various previously known methods, with atmospheric plasma spraying and vacuum um plasma spraying (English: Atmospheric Plasma Spraying, APS, as well as Vacuum Plasma Spraying, VPS), Chemical Vapor Deposition (English: Chemical Vapor Deposition, CVD), High Velocity Oxy Fuel (HVOF) and Physical Vapor Phase Deposition ( English: Physical Vapor Deposition, PVD).

WO 2006/029587 A discloses a method for producing thin, dense ceramic layers using APS.

In order to be able to guarantee the necessary protective performance in the long term, the layers should be created with as little stress as possible, without cracks and, depending on the application, as tightly as possible. Due to their high melting points, high process temperatures are required in order to apply ceramic materials in the molten state to the respective workpieces. Atmospheric Plasma Spraying (APS), Vacuum Plasma Spraying (VPS) and High Velocity Oxygen Spraying (HVOF) are the most commonly used thermal coating processes.

In plasma spraying, a spray material in the form of particles or suspensions is applied to the substrate surface to be coated using a plasma jet. A plasma is a hot gas in which the neutral particles are dissociated and ionized. A so-called plasma torch, which comprises a cathode and at least one anode, which are spaced apart from one another to form a narrow gap, is used to generate the plasma. An arc is generated between the electrodes by high-frequency ignition. A process gas flows between the electrodes, which can be, for example, argon, helium, hydrogen or nitrogen or even mixtures. see can be about two or more of these gases. With an appropriately selected process gas supply, a plasma jet, in particular several centimeters long, is formed, which is bundled and exits the nozzle of the plasma torch at high speed. The spray material in powder form or as a suspension is injected into the plasma jet. Due to the high plasma temperatures, it is melted, entrained with the plasma jet and thrown onto the substrate to be coated.

The setting of the process parameters of the spraying process is of crucial importance with regard to the quality and the efficiency of the coating produced.

With regard to plasma spraying, including the APS process, it is true that although this produces dense layers, they are usually also riddled with cracks, which can lead to premature failure or a reduced protective effect. Another disadvantage is that the layers created using the APS process are often amorphous and recrystallize during use. Due to changes in volume, this leads to stresses in the layers, which can also cause the layers to fail prematurely, or gross cracks form, which massively reduces the protective effect, especially for use as an EBC. Furthermore, high process temperatures lead to partial evaporation of the layer material and thus often to the formation of foreign phases in the applied layers that are difficult to control.

Alternative thermal coating processes such as high-velocity oxy-fuel spraying (HVOF) have the disadvantage that they cause increased coating costs due to high investment, maintenance and usage costs. Proceeding from the prior art, it is an object of the present invention to specify a method for producing ceramic layers in particular with properties optimized compared to the prior art, which can be carried out with comparatively little effort and in particular comparatively cost-effectively.

This object is achieved with a method of the type mentioned at the outset in that the burner nozzle is characterized by a nozzle diameter or a minimum nozzle diameter in the range from 4 mm to 8 mm, in particular 5 mm to 8 mm, preferably 5 mm to 7 mm, and that the process gas flow is at least 40 slpm. Slpm stands here in a manner known per se for standard liters per minute.

It has been shown that by reducing the nozzle diameter of the plasma torch (can also be referred to as plasma generator) - compared to the nozzle diameters of conventional plasma spray coating systems - and by increasing the process gas flow, largely dense, crystalline and crack-free layers can be produced using plasma spraying be able. These properties of the layers are made possible in particular by the fact that the particles used are only partially melted due to the high gas velocities and relatively short residence time in the plasma torch and still have crystalline portions when they hit the substrate. Due to the high speeds achieved within the scope of the method according to the invention, one can also speak of high-speed plasma spraying or HV-APS. The high degree of crystallinity of the layers results in low recrystallization in the hot service environment and thus reduced stress and cracking. Furthermore, the high kinetic energy of the particles means that the impacting particles create a compacted layer. In particular, the torch nozzle forms that final area, in other words the end area of the plasma torch, from which the plasma jet emerges during operation and which accordingly faces or faces the substrate to be coated. It can be formed by the anode of the plasma torch or, in the case of several anodes, by the anodes of the plasma torch or a section thereof, in particular on the outlet side. The nozzle can also be a separate component or element from the anode(s), which is then expediently arranged (immediately) following the anode(s). The nozzle is preferably at least essentially ring-shaped and defines a flow channel or flow channel section. The nozzle generally defines an outlet-side end section of a flow channel defined overall by the plasma torch.

The nozzle diameter means the inner diameter of the nozzle. In particular, the diameter of the flow channel or flow channel section defined by the nozzle.

It is possible that the burner nozzle is characterized by a nozzle diameter that remains the same over its expansion in the direction of the gas or plasma flow (flow direction). It can be, for example, a cylindrical nozzle or a nozzle with a cylindrical flow channel (section). The nozzle diameter is then the same everywhere over the nozzle extension and the constant nozzle diameter, which is the same everywhere, lies according to the invention in the aforementioned ranges.

Alternatively, the nozzle diameter can also change. In the case of a variable nozzle diameter, the minimum nozzle diameter is to be taken into account, which according to the invention is then in the stated range. Of the The nozzle diameter can increase, for example, in the direction of the exit end of the nozzle. The minimum nozzle diameter would then be present at the nozzle inlet and the maximum nozzle diameter at the nozzle outlet. Of course, the diameter can also first decrease over the nozzle extension and then increase again, so that the minimum nozzle diameter would be given at a position between the nozzle inlet and the nozzle outlet. A conical taper in the direction of the nozzle outlet would also be conceivable. Then the nozzle would have its maximum diameter at the entrance and its minimum diameter at the exit.

When carrying out the method according to the invention, preference is given to producing crystalline or partially crystalline or largely crystalline coatings. Largely crystalline is to be understood in particular as meaning that coatings are produced which are at least 50%, preferably at least 60%, particularly preferably at least 80% crystalline. The percentage values relate in particular to the mass fraction.

By using the method according to the invention, for example, particularly dense and/or partially crystalline silicon, silicate, aluminate, hafnate layers or perovskite layers or mixtures thereof can be produced as the coating or as part of the coating. Layers obtained in the manner according to the invention have improved microstructures which ensure an improved protective effect and a longer service life of the layers compared to layers sprayed with conventional PS, in particular APS. The implementation of the method according to the invention is very economical, in particular significantly more profitable than methods that use the HVOF process. Particularly dense is to be understood in particular as meaning layers which are distinguished by a porosity of at most 15%, preferably at most 10%, particularly preferably at most 5%. It has proven to be particularly suitable if atmospheric plasma spraying (APS) is used within the scope of the method according to the invention. This is also because the costs associated with atmospheric plasma spraying are particularly low in comparison. However, it cannot be ruled out that the plasma spraying takes place under reduced pressure, i.e. under vacuum, i.e. the VPS is used.

The method according to the invention has also proven to be particularly advantageous for obtaining coatings which, when produced by means of plasma spraying under conventional process parameters, tend to be deposited amorphously and which should or must be particularly dense for a given application, in particular a porosity of should or must have a maximum of 15%, preferably a maximum of 10%, particularly preferably a maximum of 5%. This is possible with the procedure according to the invention.

The process gas flow is expediently that through the burner nozzle.

A preferred embodiment of the method according to the invention is characterized in that the process gas stream 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. In other words, a process gas flow of a level in the range mentioned is set. An upper limit of the process gas stream can be 400 slpm or 500 slpm, for example. It has proven to be particularly economical if the process gas flow is a maximum of 200 slpm. Values from this range have proven to be particularly suitable in the context of the method according to the invention. A particularly high gas velocity and a particularly short dwell time in the plasma torch are achieved. As a result, particularly dense coatings can be obtained which are characterized by a high degree of crystallinity.

The nozzle diameter and the process gas flow are preferably selected in such a way that a gas velocity of at least 1250 m/s, in particular in the range from 1250 m/s to 2500 m/s, is obtained in the burner nozzle. In this case, it applies in particular that such a speed is achieved at least in the area of the minimum nozzle diameter. In particular in the event that the nozzle diameter remains the same, this can of course also apply over the entire extent of the nozzle.

In order to obtain process gas streams in the areas mentioned, conventional means known in principle from the prior art can be used. For example, at least one compressed gas tank can be used in combination with a mass flow controller.

Argon, helium, hydrogen or nitrogen in particular have proven to be suitable process gases. Of course, a mixture of two or more of these gases can also be used as the process gas. The process gas flow is to be understood as meaning the total flow of process gas, even if several process gases are used in a mixture.

Of course, both single-layer and multi-layer coatings can be produced with the method according to the invention. Several layers can be deposited one on top of the other, as is already well known from the conventional production methods. Provision can also be made for the coating to be produced in one transition, in other words with only one traversing of the area to be coated. In this case, it is preferably provided that a feed rate of the spray material of at least 50 g/min is set.

The method according to the invention also makes it possible to produce particularly thick layers, in particular those of at least 100 micrometers, in just one coating pass. Comparatively thick layers can thus be obtained with only one pass over the area to be coated and thus a combination of particularly good protective effect with particularly little effort.

In particular, one can be used as a spray material that comprises or is provided by at least one rare earth silicate, for example Yb2Si2O7. These materials have proven particularly useful for EBCs. They are characterized, for example, by an adapted thermal expansion coefficient and high chemical compatibility with SiC-based substrates. They are stable at high temperatures and offer increased corrosion resistance to water.

Alternatively or additionally, it can be provided that a spray material is used which comprises or is provided by at least one rare earth aluminate, preferably Y3Al5O12 and/or YAIO3 and/or LaMgAl11O19. These materials have also proven particularly useful for EBCs. They are characterized, for example, by an adapted thermal expansion coefficient and high chemical compatibility with Al2O3-based substrates and substrates based on Ni-based materials, including those with previously applied adhesion promoter layers, for example made of MCrAlY (M=Ni, Co) and/or Pt-Al and possibly other intermediate storage). They are stable at high temperatures and offer increased corrosion resistance to water.

The following have proven to be particularly suitable spray materials or components of spray materials: Si with doping and/or admixture of Hf, rare earth silicates SE-SIO5, SE-SI2O7 with SE=Yb, Y, La, Gd, Lu, Sc, and/or Mixtures/co-dopings thereof, aluminum silicates/mullite SIO2-AI2O3 (mixed series), optionally with SE dopings, SE aluminates with perovskite, garnet, or monoclinic structure: SE-AI-O3,SE3-AI5- O12, SE4-AI2-O9, with SE see above, aluminates with hexa-aluminate structure such as LaMgAI11O19, LaLiAH 1018.5, (complex) perovskites such as SrZrO3, BaZrO3, La(AI0.25Mg0.5.Ta0.25) 03, Ba(MgO.33TaO.66)03 or with fractional numbers.

It has proven to be particularly advantageous if a spray material is used which comprises or is provided by at least one rare earth hexaaluminate, in particular LaMgAl11O19.

The spray material can include only one material or a mixture of materials. Purely by way of example, it should be mentioned that it comprises a mixture of two or more different rare earth silicates and/or two or more different rare earth hexaaluminates or is provided by such a mixture. For example, a mixture of one or more rare earth silicates and one or more rare earth hexaaluminates is also conceivable. Spray materials with or made of rare earth silicates have proven to be particularly suitable, for example, when coatings are to be produced on substrates made of fiber composite materials, as is often the case in the space sector, for example. Spray materials with or made of rare earth aluminates have proven to be particularly suitable, for example, when coatings on substrates with or made of nickel, for example with or made of nickel-based superalloys, and/or with or made of (fully oxidic) ceramic fiber composite materials based on aluminum oxide/aluminum silicate/zirconium dioxide, as is often the case in the field of turbine technology. In particular, they have a suitably adapted thermal expansion coefficient for these materials.

Even if the method according to the invention has proven to be particularly suitable for obtaining ceramic coatings, it cannot be ruled out that non-ceramic coatings with optimal properties can be obtained with this method.

It has also proved useful if a spray material with an average particle diameter of at most 80 micrometers, in particular at most 50 micrometers, preferably at most 40 micrometers, particularly preferably at most 30 or at most 25 micrometers, is used. For example, it can also be provided that the spray material is characterized by an average particle diameter of at least 15 micrometers or at least 10 micrometers or at least 5 micrometers. An average particle diameter can be determined, for example, in a manner known per se by laser diffractometry, in particular with Horiba LA-950 V2.

It has proven particularly suitable if a spray material with an average particle diameter of less than 30 micrometers is used. In particular, a spray material with an average particle diameter in the range from 15 microns to 29 microns, preferably 10 microns to 29 microns, particularly preferably 15 microns to 29 microns, can be used. A preferred production method for a spray material, in particular in powder form, is agglomerated and sintered. The method according to the invention can correspondingly include that first of all the spray material, in particular in powder form, is produced, preferably by agglomeration and sintering taking place. Also melted or sintered and broken powder (English: fused and crushed) can be used. The method according to the invention can correspondingly include that first of all the spray material, in particular in powder form, is produced by melting and/or sintering and breaking.

Layers obtained according to the invention can form a complete protective coating, such as EBC, or, for example, also only a part of such.

The substrate provided can be uncoated or already have a (partial) coating. For example, it has proven to be suitable if a cover layer, for example a Yb2Si2O7 cover layer for an EBC system, is produced by carrying out the method according to the invention. The coating produced according to the invention then forms part of an EBC layer system.

As far as the spraying distance between the burner nozzle and the substrate is concerned, it has proven to be particularly suitable if this is in the range from 60 mm to 200 mm, in particular 70 mm to 180 mm, preferably 80 mm to 140 mm. It can particularly preferably be 100 mm or 120 mm. Another example of a suitable spray distance is 80 mm.

The current can be, for example, 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 375 A or 450 A or 470 A. The unit symbol A is there in a well-known manner for amperes. The current is expediently the working current that is used to at least partially ionize the process gas between the cathode and anode(s) of the plasma torch and thus to generate a plasma.

In a further preferred embodiment, the burner speed is a maximum of 2000 mm/s. It is in particular in the range from 100 mm/s to 1500 mm/s, preferably from 400 mm/s to 600 mm/s. It is particularly preferably 250 mm/s or 500 mm/s. The torch speed is in particular the relative speed between the plasma torch and the substrate to be coated during the coating process. This is expediently in the lateral direction parallel to the surface of the substrate to be coated. The movement is usually realized by moving the plasma torch relative to the substrate, for example by means of a robot on which the plasma torch is mounted. The plasma torch is then moved at a speed in the aforementioned ranges during the coating process.

It has proven to be particularly suitable for the delivery rate of the spray material, in particular in powder form, if it is at least 5 g/min, in particular at least 10 g/min, in other words is selected or set accordingly. For example, it can be 10 g/min or 30 g/min or 90 g/min, which has proven to be very suitable. It may also be the case that the delivery rate of the spray material is a maximum of 150 g/min.

Conventional means known in principle from the prior art can be used for conveying the spray material. It has proven to be suitable, for example, if the spray material is sprayed using a conveyor gases in the range of 2 bar to 5 bar and is conveyed/supplied using a powder feeder.

Before and/or during the application of the coating, the substrate is expediently heated. Provision can be made, for example, for the substrate to be preheated at least in sections to a temperature of at least 200° C. before the coating is applied.

Alternatively or additionally, the substrate can be heated at least in sections to a temperature of at least 250° C., preferably at least 300° C., during the application of the coating. During the coating, for example, heating to a temperature in the range from 200° C. to 700° C., preferably 300° C. to 500° C., can take place. In other words, the substrate has a temperature in the range from 200° C. to 700° C., preferably 300° C. to 500° C., at least in sections during the application of the coating. The substrate can be heated to 270°C, 400°C or 500°C or even 600°C, for example. In other words, the substrate has a temperature in the range from 200° C. to 700° C., preferably 300° C. to 500° C., at least in sections during the application of the coating.

The process according to the invention has proved to be particularly suitable for obtaining coatings on substrates which comprise or consist of silicon, such as silicon carbide and/or silicon nitride. Purely by way of example, a substrate made of a fiber composite material is coated with a silicon bond coat.

Of course, other substrates with or made of other materials can also be provided and coated in the manner according to the invention. Substrates with or made of nickel, in particular with or made of a nickel-based superalloy, and/or substrates with or made of aluminum oxide-based composite materials are also suitable, for example. Such substrates can of course also have a bond coat, for example an MCrAlY bond coat (M=Ni, Co), on which a coating is then produced in a manner according to the invention.

Another particularly advantageous embodiment is characterized in that 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, and that the burner nozzle is characterized by a nozzle diameter or a minimum nozzle diameter in the range from 5 mm to 8 mm, preferably 5 mm to 7 mm, particularly preferably 6 to 7 mm, and that a spray material with an average particle diameter of at most 40 micrometers is used, in particular a spray material with an average 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 that the substrate is heated at least in sections to a temperature of at least 300°C during the application of the coating, in particular to a temperature in the region of 300° C to 700°C, preferably in the range of 300°C to 500°C. With regard to the temperature, in other words, the substrate has a temperature in the range from 200° C. to 700° C., preferably 300° C. to 500° C., at least in sections during the application of the coating.

Alternatively or additionally, it can also be provided that the spraying distance between the burner nozzle and the substrate 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 located. It has proven to be particularly advantageous if these values for spray distance and current are combined with the values for process gas flow, nozzle diameter, particle size and substrate temperature(s) mentioned in the previous paragraph.

A spray material with an average particle diameter of less than 30 micrometers is particularly preferably used in combination with the above parameters, in particular a spray material with an average particle diameter in the range from 15 micrometers to 29 micrometers, preferably 10 micrometers to 29 micrometers, particularly preferably 15 micrometers to 29 microns.

The following has proven to be a particularly suitable combination of process parameters for the method according to the invention:

Burner nozzle diameter: 4 mm to 8 mm, in particular 5 mm to 8 mm, preferably 5 mm to 7 mm, particularly preferably 5 mm or 6.5 mm

Average particle diameter at most 50 microns, of the spray material: preferably at most 30 microns or less than 30 microns

Spray distance: 70 mm to 180 mm, preferably 80 mm to 120 mm, particularly preferably 100 mm

Process gas flow: at least 40 slpm, preferably at least

50 slpm, more preferably 50 slpm Current: 300 A to 400 A, preferably 350 A to 390 A, particularly preferably 375 A

Torch speed: maximum 2000 mm/s, preferably 100 mm/s to 1500 mm/s, particularly preferably 500 mm/s

Spray material delivery rate: at least 10 g/min, preferably 30 g/min

Substrate temperature: at least 200°C during preheating, at least 250°C, preferably 270°C during coating

It has been shown that this combination of process parameters can be used, for example, to obtain protective layers, in particular with or made of at least one rare earth silicate, preferably Yb2Si2O7, and/or with or made of at least one rare earth hexaaluminate, in particular LaMgAl11O19, with a low crack density and increased crystallinity.

Another example of a particularly suitable combination of process parameters for the method according to the invention is given by:

Mean particle diameter maximum 50 microns, of the spray material: preferably a maximum of 40 microns or less than 40 microns 70 mm to 180 mm, preferably 100 mm to 150 mm, particularly preferably 120 mm

Process gas flow: at least 80 slpm, preferably at least

100 slpm, more preferably 110 slpm

Current: 400 A to 500 A, preferably 420 A to 470 A, particularly preferably 450 A

Torch speed: maximum 2000 mm/s, preferably 200 mm/s to 1000 mm/s, particularly preferably 500 mm/s

Spray material delivery rate: at least 10 g/min, preferably 30 g/min

Substrate temperature: at least 200°C during preheating, at least 300°C, preferably 400°C during coating

It has been shown that this combination of process parameters is very suitable, for example, for the production of protective layers, in particular with or from at least one rare earth silicate, preferably Yb2Si2O7, and/or with or from at least one rare earth hexaaluminate, in particular LaMgAl11O19, with high crystallinity and a particularly low proportion of foreign phases . Another particularly suitable combination of process parameters is given by:

Mean particle diameter at most 50 micrometers, of the spray material: preferably at most 30 micrometers or below 30 micrometers

Spray distance: 70 mm to 180 mm, preferably 100 mm to 150 mm, particularly preferably 120 mm

Process gas flow: at least 80 slpm, preferably at least

100 slpm, more preferably 110 slpm

Spray material delivery rate: at least 10 g/min, preferably 30 g/min

Substrate temperature: at least 200°C during preheating at least 300°C, preferably 500°C

coating

As has been shown, this combination is particularly suitable, for example, for the production of protective layers with low porosity, in particular from a mixture of rare earth silicates, and/or with or from at least one rare earth hexaaluminate, in particular LaMgAl11O19, for example RE disilicates and - Monosilicates, in particular Yb2Si2O7 and Yb2SiO5.

Yet another particularly suitable combination of process parameters is given by:

Average particle diameter at most 50 microns, of the spray material: preferably at most 40 microns or less than 40 microns

Spray distance: 80 mm to 140 mm, preferably 100 mm to 130 mm, particularly preferably 120 mm

Process gas stream: at least 100 slpm, preferably at least 150 slpm, particularly preferably 170 to 180 slpm Current: 400 A to 500 A, preferably 420 A to 470 A, particularly preferably 450 A

Torch speed: maximum 500 mm/s, preferably 150 mm/s to 350 mm/s, particularly preferably 250 mm/s

Spray material delivery rate: at least 50 g/min, preferably 90 g/min

Substrate temperature: at least 200°C during preheating, preferably 300°C, at least 300°C, preferably 420°C during coating

This combination has proven itself, for example, for the production of protective layers, in particular with or from at least one rare earth silicate, preferably Yb2Si2O7, and/or with or from at least one rare earth hexaaluminate, in particular LaMgAl11O19, and in particular with a thickness of at least 100 micrometers using just one individual coating process proved to be particularly suitable.

Mean particle diameter maximum 80 microns, of the spray material: preferably a maximum of 30 microns or less than 30 microns

Spray distance: 70 mm to 150 mm, preferably 80 mm

Process gas flow: at least 40 slpm, preferably at least 50 slpm, particularly preferably 50 slpm AR and 6 slpm He

Current: 350 A to 550 A, preferably 470 A

Torch speed: maximum 2000 mm/s, preferably 150 mm/s to 350 mm/s, particularly preferably 250 mm/s

Spray material delivery rate: at least 5 g/min, preferably 10 g/min

Substrate temperature: at least 200°C for preheating, at least 300°C for coating, preferably 600°C for coating

This combination has proven to be particularly useful for the production of dense, crystalline Y3Al5O12 coatings or coatings with or made of at least one rare earth hexaaluminate, in particular LaMgAl11O19, on substrates with or made of nickel, in particular with or made of nickel-based superalloys proven suitable. The combination of process parameters can be used, for example, to obtain a Y3Al5O12 top layer of a TBC system to protect a corresponding substrate. A further object of the invention is a component comprising a substrate and a coating which was obtained by carrying out the method according to the invention.

With regard to the configurations of the invention, reference is also made to the dependent claims and to the following description of several exemplary embodiments with reference to the attached drawing. In the drawing shows:

FIG. 1 shows a purely schematic block diagram with the steps of five exemplary embodiments of the method according to the invention;

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

FIG. 3 shows a micrograph of a coating obtained according to a first exemplary embodiment of the method according to the invention;

FIG. 4 shows an X-ray diffractogram associated with the coating according to FIG. 3;

FIG. 5 shows a micrograph of a coating obtained with a nozzle diameter of 9 mm; FIG. 6 shows an X-ray diffractogram associated with the coating according to FIG. 5;

FIG. 7 shows a micrograph of a coating obtained according to a second exemplary embodiment of the method according to the invention;

FIG. 8 shows an X-ray diffractogram associated with the coating according to FIG. 7;

FIG. 9 shows a micrograph of a coating obtained according to a third exemplary embodiment of the method according to the invention;

FIG. 10 shows an X-ray diffractogram associated with the coating according to FIG. 9;

FIG. 11 shows a micrograph of a coating obtained according to a fourth exemplary embodiment of the method according to the invention;

FIG. 12 shows an X-ray diffractogram associated with the coating according to FIG. 11;

FIG. 13 shows a micrograph of a coating obtained according to a fourth exemplary embodiment of the method according to the invention; and

FIG. 14 shows an X-ray diffractogram associated with the coating according to FIG.

Five exemplary embodiments of the method according to the invention for producing a coating are described below. In all examples, a substrate 1 is provided in a first step S1 (cf. FIG. 1). The first to fourth exemplary embodiments involve a substrate 1 with silicon, specifically a substrate 1 made of a fiber composite material with a silicon adhesion promoter layer (English: bond coat), on which the coating is produced in each case. In contrast, in the fifth exemplary embodiment, 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 can only be seen in the purely schematic, highly simplified FIG.

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

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

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 from one another to form a narrow gap. In the examples described here, the plasma torch 2 has three anodes 8 . All five exemplary embodiments are the TriplexPro-210 model from Oerlikon Metco, which is to be understood purely as an example.

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 is, and there is a gas discharge 9. With a correspondingly selected supply of process gas, the plasma jet 4 is formed, which emerges from the nozzle 3 of the plasma torch 2 in a bundled manner and at high speed. The powdered spray material 5 is injected from the side into the plasma jet 4 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 also indicated in FIG. 2 by arrows. The spray material 5 in powder form is melted due to the high plasma temperatures, is entrained with the plasma jet 4 and spun onto the substrate 1 to be coated. As a result, a coating 12 is obtained (step S3).

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. In the example described here, these include at least one compressed gas bottle and a mass flow controller.

As can be seen, the torch nozzle 3 forms that final area, in other words the end area of the plasma torch 2, from which the plasma jet 4 emerges during operation and which accordingly faces the substrate 12 to be coated or faces 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 (immediately) following the anodes. This is the case in the example shown in FIG. The nozzle 3 is given here by an annular element which defines a flow channel 14 . The flow channel 14 defined by the nozzle 3 forms the outlet-side end section 14 of the burner flow channel 15 defined overall by the plasma torch 2. In accordance with the invention, the burner 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 the present case, the nozzle diameter D of the burner nozzle 3 is 6.5 mm in all four examples. As can be seen, the nozzle diameter D is the diameter of the flow channel 14 defined by the nozzle 3. It should be noted that the nozzle 3 in the present case defines a cylindrical flow channel 14 and thus has an inner diameter D that is constant over its entire extent in the gas/plasma flow direction . The nozzle diameter D is 6.5 mm everywhere. This is not necessarily the case. Rather, as an alternative to this, nozzles with a variable nozzle diameter can also be used. Then it applies that the minimum nozzle diameter is in the specified ranges.

In all exemplary embodiments, a process gas flow of at least 40 slpm is also set according to the invention.

The process parameters selected within the scope of the five exemplary embodiments and the layers 12 produced are discussed in more detail below.

Example 1 :

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

A rare earth silicate, in this case Yb2Si2O7, in powder form is used as spray material 5 . For example, a spray material 5 can also be used that contains at least one rare earth hexaaluminate, in particular which includes or is provided by LaMgAI11019. A preferred manufacturing method used here for the powder 5 is agglomerated and sintered. The powder 5 has an average particle diameter of less than 50 microns, less than 30 microns has proven to be particularly suitable. In the present case, this is 20 micrometers.

Furthermore, a spray distance Ds (cf. FIG. 2) in the range from 70 mm to 180 mm is selected, in this case 100 mm.

A total flow of at least 40 slpm, in particular at least 50 slpm, is set as the process gas flow. In the present case, this is chosen to be 50 slpm. Argon is used as the process gas 10 in this example.

The current is in the range from 300 A to 400 A, in this case it is 375 A.

The burner speed is selected at a maximum of 2000 mm/s, here it is 500 mm/s.

The delivery rate of the spray material 5 is chosen to be at least 10 g/min, specifically 30 g/min here.

During the preheating in step S2, the substrate 1 is brought to a temperature of at least 200°C, in the present case to approximately 300°C.

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

The figure 3 shows a micrograph of the resulting coating 12 made of Yb2Si2O7 on the by a fiber composite material with the Silicon bond coat given substrate 1. The coating has a homogeneous microstructure with high density and very fine pores. Only short, unconnected cracks appear. An X-ray diffractogram measurement (XRD measurement, cf. FIG. 4) shows an increased degree of crystallinity of 10% after a Rietveld refinement. The degree of crystallinity is abbreviated 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 manner known per se, the angle at which the intensity of the diffracted X-ray radiation is measured in relation to the angle of incidence (angle of incidence=angle of emergence in a Bragg arrangement).

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 an associated X-ray diffractogram with a predominantly amorphous component that can be seen. Here the current was 450 A, the process gas flow was 50 slpm argon, the spray distance Ds was 80 mm and the torch speed was 500 mm/s.

Example 2:

According to the second exemplary embodiment, a protective coating 12 with high crystallinity and a particularly low proportion of foreign phases is produced.

A rare earth silicate, in this case Yb2Si2O7, in powder form is used as spray material 5 . For example, a spray material 5 can also be used which comprises or is provided by at least one rare earth hexaaluminate, in particular LaMgAl11O19. a preferred The manufacturing method used here for the powder 5 is agglomerated and sintered. The powder 5 has an average particle diameter of less than 50 microns, less than 40 microns has proven to be particularly suitable. In the present case, this is 30 micrometers.

Furthermore, a spraying distance Ds in the range of 70 mm to 180 mm is selected, in this case 120 mm.

A total flow of at least 80 slpm, in particular at least 100 slpm, is set as the process gas flow. In the present case, this is chosen to be 110 slpm. Argon is used as the process gas 10 .

The current is in the range of 400 A to 500 A, in this case it is 450 A.

The burner speed is selected at a maximum of 2000 mm/s, here it is 500 mm/s.

During the actual coating process in step S3, the substrate 1 is heated to at least 300° C., to approximately 400° C. in the exemplary embodiment described here.

A special feature of this example is that this layer 12 can be produced with a particularly small proportion of the secondary phase Yb2Si2O7. FIG. 7 shows the resulting coating made from Yb2Si2O7 on the substrate 1 provided by a fiber composite material with the silicon bond coat. The coating has a homogeneous microstructure with high density and very fine pores. Only short, unconnected cracks appear. An XRD measurement (cf. FIG. 8) shows an increased degree of crystallinity of 92% after a Rietveld refinement. 98% Yb2Si2O7 and 2% Yb2SiO5 were determined as crystalline phases.

Example 3:

According to the third embodiment, a low porosity protective coating 12 is made of a mixture of fine Yb silicate powders.

A mixture of rare earth silicates, preferably of RE disilicates and monosilicates in powder form, is used as the spray material 5 . A mixture of Yb2Si2O7 and Yb2SiO5 is used here. A mixture of 75% Yb2Si2O7 and 25% Yb2SiO5 is used here, whereby this is to be understood as an example. For example, a spray material 5 can also be used which comprises or is provided by at least one rare earth hexaaluminate, in particular LaMgAl11O19.

The powder 5 has an average particle diameter of less than 50 microns, less than 30 microns has proven to be particularly suitable. In the present case, this is 20 micrometers. A preferred manufacturing method used here for the powder 5 is agglomerated and sintered. Furthermore, a spraying distance Ds in the range of 70 mm to 180 mm is selected, in this case 120 mm.

The current is in the range of 400 A to 500 A, in this case it is 450 A.

The burner speed is selected at a maximum of 2000 mm/s, here it is 500 mm/s.

During the actual coating process in step S3, the substrate 1 is heated to at least 300° C., to approximately 500° C. in the exemplary embodiment described here.

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

FIG. 9 shows the resulting coating 12 made from 75% Yb2Si2O7 and 25% Yb2SiO5 on the substrate 1 provided by a fiber composite material with the silicon bond coat. The coating 12 has a homogeneous microstructure with high density and low porosity. Only short, unconnected cracks and isolated coarse pores appear. An XRD measurement (cf. FIG. 10) gives a degree of crystallinity of 96% after Rietveld refinement. 75% Yb2Si2O7 and 25% Yb2SiO5 were determined as crystalline phases.

Example 4:

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

A rare earth silicate, in this case Yb2Si2O7, in powder form is used as spray material 5 . For example, a spray material 5 can also be used which comprises or is provided by at least one rare earth hexaaluminate, in particular LaMgAl11O19. The powder 5 has an average particle diameter of less than 50 microns, less than 40 microns has proven to be particularly suitable. In the present case, this is 30 microns. A preferred manufacturing method used here for the powder 5 is agglomerated and sintered.

Furthermore, a spraying distance Ds in the range of 80 mm to 140 mm is selected, in this case 120 mm.

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

The current is in the range of 400 A to 500 A, in this case it is 450 A. The burner speed is selected at a maximum of 500 mm/s, here it is 250 mm/s.

The delivery rate of the spray material 5 is chosen to be at least 50 g/min, specifically 90 g/min here.

During the actual coating process in step S3, the substrate 1 is heated to at least 300° C., to approximately 420° C. in the exemplary embodiment described here.

A special feature of this example is that a comparatively thick layer 12 of, for example, 150 microns can be produced with a transition.

FIG. 11 shows a micrograph of the resulting coating 12 made from Yb2Si2O7 on the substrate 1 provided by a fiber composite material with the silicon bond coat. The coating 12 has a homogeneous microstructure with high density and very fine pores. No cracks appear. An XRD measurement (cf. FIG. 12) gives a degree of crystallinity of 96% after a Rietveld refinement. 95% Yb2Si2O7 and 5% Yb2SiO5 were determined as crystalline phases.

Example 5:

According to exemplary embodiment 5, a dense, crystalline Y3AI5O12 top layer for a TBC system for protecting a substrate 1 made of a nickel-based material, in particular a nickel-based su- pearl alloy, manufactured with a MCrAIY bond coat (M=Ni, Co). Correspondingly, as noted above, within the framework of the fifth exemplary embodiment, a different substrate 1 of a corresponding configuration is provided in step S1.

Another difference is 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 can also be used which comprises or is provided by at least one rare earth hexaaluminate, in particular LaMgAl11O19. The powder 5 has an average particle diameter of no more than 80 microns, and no more than 30 microns has proven to be particularly suitable. In the present case, this is 30 microns. A preferred manufacturing method used here for the powder 5 is agglomerated and sintered.

Furthermore, a spraying distance Ds in the range of 70 mm to 150 mm is selected, in this case 80 mm.

A total flow of at least 40 slpm, in particular at least 50 slpm, is set as the process gas flow. In the present case, this is chosen to be 56 slpm. A mixture of argon and helium is used as the process gas 10 . 50 slpm argon and 6 slpm helium are used.

The current is in the range from 350 A to 550 A, in this case it is 470 A.

The burner speed is selected at a maximum of 2000 mm/s, here it is 250 mm/s. The delivery rate of the spray material 5 is chosen to be at least 5 g/min, specifically 10 g/min here.

During the actual coating process in step S3, the substrate 1 is heated to at least 300° C., to approximately 600° C. in the exemplary embodiment described here.

FIG. 13 shows a micrograph of the resulting coating 12 made from Y3Al5O12 on the substrate 1 made from a nickel-based material with an MCrAIY bond coat (M=Ni,Co). The coating 12 has a homogeneous microstructure with a high density and very fine pores. Only short, unconnected cracks appear. An XRD measurement (cf. FIG. 14) shows a degree of crystallinity of more than 60% after a Rietveld refinement.

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

Claims

37 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), in particular by 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 a supplied spray material (5) is applied to the substrate (1) to obtain the coating (12) with the plasma jet (4). characterized in that the burner 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 that the process gas flow is at least 40 slpm.

2. The method according to claim 1, characterized in that the process gas stream 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. The method according to claim 1 or 2, characterized in that a single- or multi-layer coating (12) is produced, and / or that a particularly semi-crystalline silicon or silicate or aluminate, hafnate or perovskite layer or mixtures thereof as the coating (12) or as part of the coating (12).

4. The method according to any one of the preceding claims, characterized in that a spray material (5) is used, which comprises at least one rare earth silicate, preferably Yb2Si2O7, or is given, and / or that a spray material (5) is used, the at least one Rare earth aluminate, preferably Y3AI5O12 and/or YAIO3 and/or LaMgAI11019, comprises or is provided by it.

5. The method according to any one of the preceding claims, characterized in that a spray material (5) is used, which comprises at least one rare earth hexaaluminate, in particular LaMgAH 1019, or is provided by it.

6. The method according to any one of the preceding claims, characterized in that a spray material (5) with an average 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. The method according to any one of the preceding claims, characterized in that a spray material (5) with an average particle diameter of less than 30 micrometers is used, in particular a spray material (5) with an average particle diameter in the range of 15 micrometers to 29 micrometers, preferably 10 microns to 29 microns, more preferably 15 microns to 29 microns.

8. The method according to any one of the preceding claims, characterized in that the spray distance (Ds) between the burner nozzle (3) and the substrate (1) in the range of 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. The method according to any one of the preceding claims, characterized in that 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 375 A or 450 A or 470 A amounts to.

10. The method according to any one of the preceding claims, characterized in that the burner speed is a maximum of 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, in particular is preferably 500 mm/s.

11. The method according to any one of the preceding claims, characterized in that the delivery rate of the spray material (5) is at least 5 g/min, in particular at least 10 g/min, preferably 10 g/min or 30 g/min or 90 g/min .

12. The method according to any one of the preceding claims, characterized in that the substrate (1) before the application of the coating (12) is preheated at least in sections to a temperature of at least 200 ° C, and / or that the substrate (1) during the Application of the coating (12) is heated at least in sections to a temperature of at least 250°C, preferably at least 300°C.

13. The method according to any one of the preceding claims, characterized in that the substrate (1) comprises silicon, in particular silicon carbide and/or silicon nitride, and/or that the substrate (1) comprises nickel, in particular a nickel-based superalloy, and/or or the substrate (1) comprises alumina-based composites.

14. The method as claimed in one of the preceding claims, characterized in that the coating (12) is produced in one transition, preferably with a feed rate of the spray material (5) of at least 50 g/min being set.

15. The method according to any one of the preceding claims, characterized in that 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, that the burner nozzle (3) through a nozzle diameter (D) or a minimum nozzle diameter (D) in the range of 5 mm to 8 mm, preferably 5 mm to 7 mm, particularly preferably 6 to 7 mm, and that a spray material (5) with an average particle diameter of at most 40 micrometers is used, in particular a spray material with an average 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 that the substrate (1) during the Application of the coating (12) is at least partially heated to a temperature of at least 300 ° C, in particular to a temperature r in the range from 300°C to 700°C, preferably in the range from 300°C to 500°C.

16. The method according to claim 15, characterized in that the spraying distance (Ds) between the burner 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 is preferably in the range from 400 Å to 550 Å.

17. Component comprising a substrate (1) and a coating (12) which was obtained by carrying out the method according to any one of the preceding claims.