Method for preparing high-entropy rare earth tantalate thermal protection coating through atmospheric plasma spraying

Abstract

The invention relates to a method for preparing a high-entropy rare earth tantalate thermal protection coating through atmospheric plasma spraying, and belongs to the technical field of ceramic coatings. The method comprises the steps that NiCrCoAlY powder is sprayed to a base body through atmospheric plasma spraying to prepare a bonding layer, then HE-RETaO4 powder for spraying is sprayed to the bonding layer through atmospheric plasma spraying, a ceramic bottom layer and a ceramic surface layer are prepared respectively, and the ceramic bottom layer and the ceramic surface layer jointly form the high-entropy rare earth tantalate thermal protection coating. According to the method, aiming at the characteristics of (Nd < 0.2 > Dy < 0.2 > Ho < 0.2 > Y < 0.2 > Er < 0.2 >), the particle size of HE-RETaO4 powder is regulated and controlled, atmospheric plasma spraying process parameters are optimized, and powder characteristics, spraying parameters and deposition dynamic behaviors are synergistically optimized, so that the high-entropy rare earth tantalate thermal protection coating with low porosity, high density and strong interlayer binding force is obtained.

Description

Technical Field

[0001] The invention relates to a method for preparing a high-entropy rare earth tantalate thermal protective coating by atmospheric plasma spraying, and belongs to the technical field of ceramic coatings. Background Art

[0002] Thermal protection coatings (TPCs) are widely used in advanced aircraft engines to protect critical components at extremely high temperatures, ensuring the safety and reliability of the engine during flight. Conventional coatings made from yttria-partially stabilized zirconia (YSZ) TPC materials have a low high-temperature resistance limit. At service temperatures exceeding 1200°C, YSZ undergoes a phase transition from the monoclinic phase (m-ZrO2) to the tetragonal phase (t-ZrO2), accompanied by a large thermal expansion volume change. This can accelerate the propagation of cracks within the coating, leading to coating spalling.

[0003] High entropy rare earth tantalates (Nd 0.2 Dy 0.2 Ho 0.2 Y 0.2 Er 0.2 The significant difference in rare earth cation radius in the )TaO4 (HE-RETaO4) powder material leads to considerable lattice distortion, which greatly enhances phonon scattering and makes the HE-RETaO4 ceramic exhibit excellent thermophysical properties. The thermal expansion coefficient of the material at 1000℃ is 10.3K -1 ×10 -6 K -1 , the thermal conductivity at 800℃ is 1.43W·m -1 ·K -1 When the service temperature exceeds 1400°C, HE-RETaO4 undergoes a ferroelastic phase transition from monoclinic to tetragonal phase without being accompanied by a large volume change. Furthermore, the unique ferroelastic domains in HE-RETaO4 can alleviate thermal stress within the coating and improve the thermal insulation limit of the coating. Therefore, this material has attracted much attention in the field of high-temperature thermal protective coatings.

[0004] However, there is currently no technology that can prepare high-entropy rare earth tantalate powder materials into high-entropy tantalate thermal protective coatings with good thermal protection effects. The existing preparation technology has the following bottlenecks:

[0005] Limitations of traditional fabrication processes: While electron beam physical vapor deposition (EB-PVD) can produce columnar crystal structures to enhance thermal shock resistance, its equipment costs are high and deposition rates are low. Sol-gel or solid-phase sintering methods require high-temperature heat treatment (>1500°C), which can lead to grain coarsening, residual stress accumulation, and reduced interfacial bonding strength. Coatings produced using conventional atmospheric plasma spraying (APS) typically have high porosity and weak interlayer bonding, making them susceptible to crack initiation and propagation failure under thermal loads.

[0006] Therefore, there is an urgent need to develop an efficient, low-cost preparation method suitable for high-entropy rare earth tantalate systems to achieve the controllable preparation of highly dense, low-defect thermal protective coatings. Summary of the Invention

[0007] In order to overcome the defects of the thermal protective coatings prepared by atmospheric plasma spraying, such as high porosity and weak interlayer bonding, the present invention aims to provide a method for preparing high entropy rare earth tantalate thermal protective coatings by atmospheric plasma spraying. The method comprises the following steps: 0.2 Dy 0.2 Ho 0.2 Y 0.2 Er 0.2 ), that is, the characteristics of the material HE-RETaO4. By creatively regulating the particle size of HE-RETaO4 powder and optimizing the spraying process parameters, the powder characteristics, spraying parameters and deposition dynamics are synergistically optimized to obtain a high-entropy rare earth tantalate thermal protective coating with low porosity, high density and strong interlayer bonding.

[0008] To achieve the purpose of the present invention, the following technical solutions are provided.

[0009] A method for preparing a high-entropy rare earth tantalate thermal protective coating by atmospheric plasma spraying, the method comprising the following steps:

[0010] (1) The clean surface of the substrate to be sprayed is sandblasted to make its surface roughness Ra 6μm~7μm.

[0011] In step (1):

[0012] The substrate is a metal or alloy, preferably a high-temperature nickel-based alloy.

[0013] A clean substrate surface to be sprayed can be obtained by the following methods:

[0014] The surface of the substrate to be sprayed is cleaned with acetone or ethanol to remove impurities such as dust and oil attached to the surface of the substrate to obtain a clean substrate surface to be sprayed.

[0015] Sand blasting can use 30-40 mesh corundum sand for surface sand blasting, and use compressed air to blow away the remaining corundum sand particles.

[0016] (2) The substrate after sandblasting is preheated to 350°C to 400°C, and NiCrCoAlY powder is sprayed onto the surface of the substrate to be sprayed by atmospheric plasma spraying to form a bonding layer.

[0017] In step (2):

[0018] The atmospheric plasma spraying process parameters are: spraying angle of 90°~92°, spraying distance of 100mm~105mm, current of 380A~400A, power of 32kW~33kW, flow rate of working gas argon (Ar) of 42L / min~43L / min, flow rate of auxiliary gas hydrogen (H2) of 3.5L / min~4L / min, powder feeding amount of 38g / min~40g / min, and flow rate of carrier gas nitrogen (N2) of 8L / min~9L / min.

[0019] The particle size of the NiCrCoAlY powder is 30 μm to 100 μm. The powder is kept at 90° C. to 100° C. for 30 to 40 minutes and then placed in a powder feeding device for spraying.

[0020] The thickness of the adhesive layer is 140 μm to 150 μm.

[0021] (3) preheating the substrate to 350° C. to 400° C., spraying HE-RETaO4 powder for spraying on the bonding layer by atmospheric plasma spraying to prepare a ceramic base layer with a thickness of 50 μm to 100 μm; continuing to spray HE-RETaO4 powder for spraying on the ceramic base layer by atmospheric plasma spraying to prepare a ceramic surface layer with a thickness of 120 μm to 150 μm; the ceramic base layer and the ceramic surface layer together constitute the high entropy rare earth tantalate thermal protective coating of the present invention;

[0022] Among them, the atmospheric plasma spraying process parameters of the ceramic bottom layer are: spraying angle of 90°~92°, spraying distance of 100mm~105mm, current of 485A~495A, power of 36kW~38kW, flow rate of working gas Ar gas of 44L / min~45L / min, flow rate of auxiliary gas H2 gas of 3L / min~4L / min, powder feeding amount of 40g / min~42g / min, and flow rate of carrier gas N2 gas of 9L / min~10L / min;

[0023] The atmospheric plasma spraying process parameters of the ceramic surface are: spraying angle of 90°~92°, spraying distance of 100mm~105mm, current of 400A~455A, power of 33kW~34kW, flow rate of working gas Ar gas of 41L / min~42L / min, flow rate of auxiliary gas H2 gas of 2.8L / min~3.8L / min, powder feeding amount of 38g / min~40g / min, and flow rate of carrier gas N2 gas of 9L / min~10L / min.

[0024] In step (3):

[0025] The HE-RETaO4 powder used for spraying is a high entropy rare earth tantalate (Nd 0.2 Dy0.2 Ho 0.2 Y 0.2 Er 0.2 )TaO4 powder is spray granulated and then heat treated to obtain spherical powder with a particle size of 30μm to 70μm.

[0026] The raw material composition of the spray granulation is: based on the total mass of HE-RETaO4 powder and water as 100%, the mass fraction of HE-RETaO4 powder is 62% to 65%, and the balance is water; polyvinyl alcohol is used as a binder, and the amount used is 1.8% to 2% of the HE-RETaO4 powder; ammonium polyacrylate is used as a dispersant, and the amount used is 0.8% to 1% of the HE-RETaO4 powder.

[0027] The spray granulation process parameters are: feed rate 45ml / min~50ml / min, atomization pressure 0.06MPa~0.08MPa, inlet temperature 230℃~240℃, and outlet temperature 110℃~115℃.

[0028] The heat treatment process parameters are as follows: initial temperature is 25℃~30℃, heating at a heating rate of 5℃ / min~10℃ / min to 600℃~650℃, keeping constant temperature for 3h~3.5h, then heating to 1100℃~1150℃ at a heating rate of 5℃ / min~10℃ / min, keeping constant temperature for 3h~3.5h, and then cooling with the furnace.

[0029] Before spraying, the HE-RETaO4 powder for spraying is dried at 90℃~100℃ and then placed in the powder feeding device.

[0030] Beneficial effects

[0031] (1) The present invention provides a method for preparing a high-entropy rare earth tantalate thermal protective coating by atmospheric plasma spraying. In the method, spherical powder with good fluidity is obtained by regulating the spray granulation method parameters of HE-RETaO4. Combined with the adjustment of the atmospheric plasma spraying process parameters, on the one hand, HE-RETaO4 powder can be effectively deposited, greatly improving the density of the coating; on the other hand, in view of the low iron chip transition temperature of HE-RETaO4, a layered spraying strategy is adopted, and the ceramic bottom layer and the ceramic surface layer are sprayed twice. The ceramic bottom layer adopts high-power rapid deposition to obtain a dense coating; the ceramic surface layer adopts medium-power low-speed deposition, and an iron chip structure with a toughening effect can be obtained at low temperature, and a coating that can reduce thermal stress cracks caused by rapid cooling can be obtained. The ceramic bottom layer and the ceramic surface layer together constitute the high-entropy rare earth tantalate thermal protective coating of the present invention, so that its protective life is effectively improved.

[0032] (2) The present invention provides a method for preparing a high entropy rare earth tantalate thermal protective coating by atmospheric plasma spraying, wherein the method comprises spraying a high entropy rare earth tantalate (Nd 0.2 Dy 0.2 Ho 0.2 Y 0.2 Er 0.2 )TaO4 powder is spray granulated and then heat treated to obtain spherical powder with a particle size of 30μm to 70μm. As the spraying particles for atmospheric plasma spraying, it can be fully melted, so that the prepared high-entropy rare earth tantalate thermal protective coating has a low porosity of 5% to 8%, and has the characteristics of high deposition rate, good thermal protection and low high-temperature phase change expansion rate of the coating.

[0033] (3) The present invention provides a method for preparing a high-entropy rare earth tantalate thermal protective coating by atmospheric plasma spraying. The method has good process controllability, low cost and high spraying efficiency.

[0034] (4) The present invention provides a method for preparing a high entropy rare earth tantalate thermal protective coating by atmospheric plasma spraying, wherein the high entropy rare earth tantalate (Nd 0.2 Dy 0.2 Ho 0.2 Y 0.2 Er 0.2 )TaO4 powder is subjected to heat treatment after spray granulation, and the heat treatment can enhance its cohesive strength and obtain better spraying effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a scanning electron microscope (SEM) image of the HE-RETaO4 powder used for spraying in Example 1.

[0036] Figure 2 This is a cross-sectional scanning electron microscope image of the high entropy rare earth tantalate thermal protective coating in Example 1.

[0037] Figure 3 This is a scanning electron microscope image of a cross section of the high-entropy rare earth tantalate thermal protective coating in Example 1.

[0038] Figure 4 This is a scanning electron microscope image of the ferroelastic domain structure of the high entropy rare earth tantalate thermal protective coating in Example 1.

[0039] Figure 5 This is a scanning electron microscope image of the high entropy rare earth tantalate thermal protective coating in Example 1 after plasma flame testing.

[0040] Figure 6 This is a scanning electron microscope image of the HE-RETaO4 powder used for spraying in Example 2.

[0041] Figure 7 This is a cross-sectional scanning electron microscope image of the high-entropy rare earth tantalate thermal protective coating in Example 2.

[0042] Figure 8 This is a scanning electron microscope image of the cross section of the high-entropy rare earth tantalate thermal protective coating in Example 2.

[0043] Figure 9 This is a scanning electron microscope image of the ferroelastic domain structure of the high entropy rare earth tantalate thermal protective coating in Example 2.

[0044] Figure 10 This is a scanning electron microscope image of the high entropy rare earth tantalate thermal protective coating in Example 2 after plasma flame testing.

[0045] Figure 11 This is a scanning electron microscope image of the HE-RETaO4 powder used for spraying in Comparative Example 1.

[0046] Figure 12 This is a cross-sectional scanning electron microscope image of the high entropy rare earth tantalate coating in Comparative Example 1.

[0047] Figure 13 This is a scanning electron microscope image of the high entropy rare earth tantalate coating in Comparative Example 1 after plasma flame testing. DETAILED DESCRIPTION

[0048] The present invention will be further described below in conjunction with specific embodiments. The methods described are conventional techniques in the art unless otherwise specified, and the raw materials described can be obtained from public sources unless otherwise specified. In the following examples:

[0049] Hall flowmeter is used to detect the fluidity of granulated powder;

[0050] The surface roughness was measured using a Times TR100 pocket roughness meter;

[0051] The spray gun for atmospheric plasma spraying is Ruifa GH2080 from Shanghai, China;

[0052] The microstructure morphology of the powder to be sprayed, the cross section and the cross section of the thermal protective coating prepared in the examples and comparative examples was observed using a scanning electron microscope (SEM) (FEIQuanta 200, Netherlands);

[0053] The porosity of the coatings prepared in the examples and comparative examples was measured and calculated using Image J image analysis test software;

[0054] The atmospheric plasma flame thermal shock test (RuiFa GH2080, Shanghai, China) was used to evaluate the thermal shock resistance of the coating.

[0055] Example 1

[0056] A method for preparing a high-entropy rare earth tantalate thermal protective coating by atmospheric plasma spraying, the method comprising the following steps:

[0057] (1) The surface of the GH4169 high-temperature alloy substrate to be sprayed was cleaned with analytically pure acetone to remove impurities such as dust and oil attached to the substrate surface, thereby obtaining a clean substrate surface to be sprayed; the surface of the substrate to be sprayed was sandblasted with 30-mesh corundum sand to achieve a surface roughness of Ra of 6 μm, and the corundum sand particles remaining on the substrate surface were blown away with compressed air.

[0058] (2) Preheat the sandblasted substrate to 350°C and place the substrate on a workpiece holder so that the surface to be sprayed faces the spray gun; NiCrCoAlY powder with a particle size of 30 μm to 100 μm is kept at 90°C for 30 minutes and then placed in a powder feeding device. The NiCrCoAlY powder is sprayed onto the surface of the substrate to be sprayed by atmospheric plasma spraying to form a bonding layer with a thickness of 140 μm;

[0059] The atmospheric plasma spraying process parameters for preparing the bottom layer of the bonding layer are: spraying angle of 90°, spraying distance of 100 mm, current of 380 A, power of 32 kW, flow rate of working gas Ar gas of 42 L / min, flow rate of auxiliary gas H2 gas of 3.5 L / min, powder feeding amount of 38 g / min, and flow rate of carrier gas N2 gas of 8 L / min.

[0060] (3) preheating the substrate to 350° C., spraying HE-RETaO4 powder for spraying on the bonding layer by atmospheric plasma spraying to prepare a ceramic base layer with a thickness of 50 μm; then continuing to spray HE-RETaO4 powder for spraying on the ceramic base layer by atmospheric plasma spraying to prepare a ceramic surface layer with a thickness of 150 μm, the ceramic base layer and the ceramic surface layer together constitute a high entropy rare earth tantalate thermal protective coating;

[0061] The atmospheric plasma spraying process parameters for the ceramic substrate are as follows: spray angle 90°, spray distance 100 mm, current 485 A, power 36 kW, working gas argon flow rate 44 L / min, auxiliary gas hydrogen flow rate 3 L / min, powder feeding rate 40 g / min, carrier gas nitrogen flow rate 9 L / min;

[0062] The atmospheric plasma spraying process parameters for the ceramic surface layer are: spray angle 90°, spray distance 100 mm, current 400 A, power 33 kW, working gas argon flow rate 41 L / min, auxiliary gas hydrogen flow rate 2.8 L / min, powder feeding rate 38 g / min, carrier gas nitrogen flow rate 9 L / min;

[0063] The HE-RETaO4 powder used for spraying is a high entropy rare earth tantalate (Nd 0.2 Dy 0.2 Ho 0.2 Y 0.2 Er 0.2 )TaO4 powder is spray granulated and then heat treated to obtain spherical powder with a particle size of 40μm to 60μm.

[0064] The raw material composition of the spray granulation is: based on the total mass of HE-RETaO4 powder and deionized water as 100%, the mass fraction of HE-RETaO4 powder is 62%, and the balance is deionized water; polyvinyl alcohol is used as a binder, and the amount used is 1.8% of the HE-RETaO4 powder; ammonium polyacrylate is used as a dispersant, and the amount used is 0.8% of the HE-RETaO4 powder.

[0065] The spray granulation process parameters are: feed rate 45 ml / min, atomization pressure 0.06 MPa, inlet temperature 230 °C, and outlet temperature 110 °C.

[0066] The heat treatment process parameters are as follows: the initial temperature of the muffle furnace containing the spherical powder prepared by spray granulation is 25°C, the temperature is increased to 650°C at a heating rate of 5°C / min, the temperature is kept constant for 3 hours, the temperature is then increased to 1100°C at a heating rate of 5°C / min, the temperature is kept constant for 3 hours, and then the furnace is cooled.

[0067] The HE-RETaO4 powder for spraying is dried at 90°C and then placed in the powder feeding device.

[0068] Observation test:

[0069] (1) The microscopic morphology of the HE-RETaO4 powder prepared in this embodiment for spraying was observed. Figure 1 It can be seen from the figure that the prepared powder is spherical with a particle size of 40 μm to 60 μm and a flowability of 83 s / 50 g to 93 s / 50 g, which meets the flowability requirements of atmospheric plasma spraying.

[0070] (2) The microscopic morphology of the high entropy rare earth tantalate thermal protective coating prepared in this embodiment was observed. From the SEM image of the cross section of the coating, Figure 2 It can be seen that the high entropy rare earth tantalate thermal protective coating and the bonding layer are well bonded, the powder is fully melted, and the coating is dense; from the SEM image of the coating cross section Figure 3 It can be seen that the high entropy rare earth tantalate thermal protective coating has a typical lamellar structure of atmospheric plasma spray coating, and the layers are inlaid and closely combined; Figure 4It can be seen that the high entropy rare earth tantalate thermal protective coating has a typical iron chip structure and has a good toughening effect.

[0071] (3) Image analysis test using Image J shows that the average porosity of the prepared high-entropy rare earth tantalate thermal protective coating is 7.46%.

[0072] (4) Plasma flame assessment: The prepared high entropy rare earth tantalate thermal protective coating was subjected to a thermal shock test for 200 seconds using a 1200°C plasma flame. After the temperature stabilized, the coating showed a thermal insulation of 230°C, indicating a good thermal insulation effect. Figure 5 This is a scanning electron microscope image of the high-entropy rare earth tantalate thermal protective coating after plasma flame testing, showing that no large cracks are generated in the coating after the plasma flame test, and the grains remain relatively small, which allows the coating to maintain a certain strength.

[0073] Example 2

[0074] A method for preparing a high-entropy rare earth tantalate thermal protective coating by atmospheric plasma spraying, the method comprising the following steps:

[0075] (1) The surface of the GH4169 high-temperature alloy substrate to be sprayed was cleaned with analytically pure acetone to remove impurities such as dust and oil attached to the substrate surface, thereby obtaining a clean substrate surface to be sprayed; the surface of the substrate to be sprayed was sandblasted with 40-mesh corundum sand to make the substrate surface roughness reach Ra 7 μm, and the corundum sand particles remaining on the substrate surface were blown away with compressed air.

[0076] (2) Preheat the sandblasted substrate to 400°C and place the substrate on a workpiece holder so that the surface to be sprayed faces the spray gun; NiCrCoAlY powder with a particle size of 30 μm to 100 μm is kept at 100°C for 40 minutes and then placed in a powder feeding device. The NiCrCoAlY powder is sprayed onto the surface of the substrate to be sprayed by atmospheric plasma spraying to form a bonding layer with a thickness of 150 μm;

[0077] The atmospheric plasma spraying process parameters for preparing the bonding layer are: spraying angle of 92°, spraying distance of 105 mm, current of 400 A, power of 33 kW, flow rate of working gas Ar gas of 43 L / min, flow rate of auxiliary gas H2 gas of 4 L / min, powder feeding amount of 40 g / min, and flow rate of carrier gas N2 gas of 9 L / min.

[0078] (3) preheating the substrate to 400° C., spraying HE-RETaO4 powder for spraying on the bonding layer by atmospheric plasma spraying to prepare a ceramic base layer with a thickness of 100 μm; continuing to spray HE-RETaO4 powder for spraying on the ceramic base layer by atmospheric plasma spraying to prepare a ceramic surface layer with a thickness of 120 μm, the ceramic base layer and the ceramic surface layer together constitute a high entropy rare earth tantalate thermal protective coating;

[0079] The atmospheric plasma spraying process parameters for the ceramic substrate are as follows: spray angle 92°, spray distance 105 mm, current 495 A, power 38 kW, working gas argon flow rate 45 L / min, auxiliary gas hydrogen flow rate 4 L / min, powder feeding rate 42 g / min, carrier gas nitrogen flow rate 10 L / min;

[0080] The atmospheric plasma spraying process parameters for the ceramic surface layer are: spraying angle 92°, spraying distance 105 mm, current 455 A, power 34 kW, working gas argon flow rate 42 L / min, auxiliary gas hydrogen flow rate 3.8 L / min, powder feeding rate 40 g / min, carrier gas nitrogen flow rate 10 L / min;

[0081] The HE-RETaO4 powder used for spraying is a high entropy rare earth tantalate (Nd 0.2 Dy 0.2 Ho 0.2 Y 0.2 Er 0.2 )TaO4 is subjected to powder spray granulation and then heat treated to obtain spherical powder with a particle size of 30μm to 70μm.

[0082] The raw material composition of the spray granulation is: based on the total mass of HE-RETaO4 powder and deionized water as 100%, the mass fraction of HE-RETaO4 powder is 65%, and the balance is deionized water; polyvinyl alcohol is used as a binder, and the amount used is 2% of the HE-RETaO4 powder; ammonium polyacrylate is used as a dispersant, and the amount used is 1% of the HE-RETaO4 powder.

[0083] The spray granulation process parameters are: feed rate 50 ml / min, atomization pressure 0.08 MPa, inlet temperature 240 °C, and outlet temperature 115 °C.

[0084] The heat treatment process parameters are as follows: the initial temperature of the muffle furnace containing the spherical powder prepared by spray granulation is 30°C, the temperature is increased to 600°C at a heating rate of 10°C / min, the temperature is kept constant for 3.5 hours, the temperature is then increased to 1150°C at a heating rate of 10°C / min, the temperature is kept constant for 3.5 hours, and then the furnace is cooled.

[0085] The HE-RETaO4 powder for spraying is dried at 100°C and then placed in a powder feeding device.

[0086] Observation test:

[0087] (1) The microscopic morphology of the HE-RETaO4 powder prepared in this embodiment for spraying was observed. Figure 6 It can be seen from the figure that the prepared powder is spherical with a particle size of 30 μm to 70 μm and a flowability of 78 s / 50 g to 85 s / 50 g, which meets the flowability requirements of atmospheric plasma spraying.

[0088] (2) The microscopic morphology of the high entropy rare earth tantalate thermal protective coating prepared in this embodiment was observed. From the SEM image of the cross section of the coating, Figure 7 It can be seen that the high entropy rare earth tantalate thermal protective coating and the bonding layer are well bonded, the powder is fully melted, and the coating is dense; from the SEM image of the coating cross section Figure 8 It can be seen that the high entropy rare earth tantalate thermal protective coating has a typical lamellar structure of atmospheric plasma spray coating, and the layers are inlaid and closely combined; Figure 9 It can be seen that the high entropy rare earth tantalate thermal protective coating has a typical iron chip structure and has a good toughening effect.

[0089] (3) Image J analysis showed that the average porosity of the prepared high-entropy rare earth tantalate thermal protective coating was 6.07%.

[0090] (4) Plasma flame assessment: The prepared high entropy rare earth tantalate thermal protective coating was subjected to thermal shock for 200 seconds using a 1200°C plasma flame. After the temperature stabilized, the coating was tested to have a thermal insulation temperature of 235°C, indicating a good thermal insulation effect. Figure 10 This is a scanning electron microscope image of the high-entropy rare earth tantalate thermal protective coating after plasma flame testing, showing that no large cracks are generated in the coating after the plasma flame test, and the grains remain relatively small, which allows the coating to maintain a certain strength.

[0091] Comparative Example 1

[0092] A method for preparing a high-entropy rare earth tantalate coating, comprising the following steps:

[0093] (1) The surface of the GH4169 high-temperature alloy substrate to be sprayed was cleaned with analytically pure acetone to remove impurities such as dust and oil attached to the substrate surface, thereby obtaining a clean substrate surface to be sprayed; the surface of the substrate to be sprayed was sandblasted with 30-mesh corundum sand to achieve a surface roughness of Ra of 6 μm, and the corundum sand particles remaining on the substrate surface were blown away with compressed air.

[0094] (2) Preheat the sandblasted substrate to 350°C and place the substrate on a workpiece holder so that the surface to be sprayed faces the spray gun; NiCrCoAlY powder with a particle size of 30 μm to 100 μm is kept at 90°C for 30 minutes and then placed in a powder feeding device. The NiCrCoAlY powder is sprayed onto the surface of the substrate to be sprayed by atmospheric plasma spraying to form a bonding layer with a thickness of 140 μm;

[0095] The atmospheric plasma spraying process parameters for preparing the bottom layer of the bonding layer are: spraying angle of 90°, spraying distance of 100 mm, current of 380 A, power of 32 kW, flow rate of working gas Ar gas of 42 L / min, flow rate of auxiliary gas H2 gas of 3.5 L / min, powder feeding amount of 38 g / min, and flow rate of carrier gas N2 gas of 8 L / min.

[0096] (3) preheating the substrate to 350°C, and spraying HE-RETaO4 powder on the bonding layer by atmospheric plasma spraying to prepare a high entropy rare earth tantalate coating with a thickness of 200 μm;

[0097] The atmospheric plasma spraying process parameters for the high-entropy rare earth tantalate coating are as follows: spray angle 90°, spray distance 100 mm, current 400 A, power 33 kW, working gas argon flow rate 41 L / min, auxiliary gas hydrogen flow rate 2.8 L / min, powder feed rate 38 g / min, and carrier gas nitrogen flow rate 9 L / min.

[0098] The HE-RETaO4 powder used for spraying is a high entropy rare earth tantalate (Nd 0.2 Dy 0.2 Ho 0.2 Y 0.2 Er 0.2 )TaO4 is subjected to powder spray granulation and then heat treated to obtain spherical powder with a particle size of 30μm to 70μm.

[0099] The raw material composition of the spray granulation is: based on the total mass of HE-RETaO4 powder and deionized water as 100%, the mass fraction of HE-RETaO4 powder is 50%, and the balance is deionized water; polyvinyl alcohol is used as a binder, and the amount used is 0.8% of the HE-RETaO4 powder; ammonium polyacrylate is used as a dispersant, and the amount used is 1.2% of the HE-RETaO4 powder.

[0100] The spray granulation process parameters are: feed rate 45 ml / min, atomization pressure 0.06 MPa, inlet temperature 230 °C, and outlet temperature 110 °C.

[0101] The heat treatment process parameters are as follows: the initial temperature of the muffle furnace containing the spherical powder prepared by spray granulation is 25°C, the temperature is increased to 650°C at a heating rate of 5°C / min, the temperature is kept constant for 3 hours, the temperature is then increased to 1100°C at a heating rate of 5°C / min, the temperature is kept constant for 3 hours, and then the furnace is cooled.

[0102] The HE-RETaO4 powder for spraying is dried at 90°C and then placed in the powder feeding device.

[0103] Observation test:

[0104] (1) The microscopic morphology of the HE-RETaO4 powder for spraying prepared in this comparative example was observed. Figure 11 It can be seen that the particle size and sphericity of the prepared powder are poor, and the flowability is detected to be 120s / 50g to 130s / 50g, which is not conducive to the flowability requirements of atmospheric plasma spraying.

[0105] (2) The microscopic morphology of the high entropy rare earth tantalate coating prepared in this comparative example was characterized, and the cross-sectional SEM image of the coating was obtained. Figure 12 It can be seen that the bonding between the high entropy rare earth tantalate coating and the bonding layer is poor, and the coating is not dense.

[0106] (3) Image J analysis showed that the average porosity of the prepared high-entropy rare earth tantalate coating was 10.39%.

[0107] (4) Plasma flame test: The prepared high entropy rare earth tantalate coating was subjected to thermal shock for 200 seconds using a 1200°C plasma flame. Figure 13 This is a microscopic scanning electron microscope image of the high-entropy rare earth tantalate coating after plasma flame testing, which shows that large cracks are generated in the coating after the plasma flame test, which will accelerate the peeling of the coating; compared with the layered spray molding in Examples 1 and 2, the direct spray molding in this comparative example is not conducive to regulating the relationship between the density and thermal stress of the coating. It is difficult to have high density and low thermal stress at the same time, which is not conducive to the use effect of the coating.

Claims

1. A method for preparing a high-entropy rare earth tantalate thermal protective coating by atmospheric plasma spraying, characterized in that: (1) Sandblast the clean surface of the substrate to be sprayed to a surface roughness Ra of 6 μm to 7 μm; (2) preheating the sandblasted substrate to 350°C to 400°C, and spraying NiCrCoAlY powder onto the surface of the substrate to be sprayed by atmospheric plasma spraying to obtain a bonding layer with a thickness of 140 μm to 150 μm; (3) Preheating the substrate to 350°C to 400°C, spraying HE-RETaO4 powder for spraying on the bonding layer by atmospheric plasma spraying to prepare a ceramic base layer with a thickness of 50μm to 100μm; spraying HE-RETaO4 powder for spraying on the ceramic base layer by atmospheric plasma spraying to prepare a ceramic surface layer with a thickness of 120μm to 150μm; the ceramic base layer and the ceramic surface layer together constitute a high entropy rare earth tantalate thermal protective coating.

2. The method for preparing a high-entropy rare earth tantalate thermal protective coating by atmospheric plasma spraying according to claim 1, characterized in that: The atmospheric plasma spraying process parameters of the ceramic bottom layer are: spraying angle 90°~92°, spraying distance 100mm~105mm, current 485A~495A, power 36kW~38kW, working gas Ar flow rate 44L / min~45L / min, auxiliary gas H2 flow rate 3L / min~4L / min, powder feeding amount 40g / min~42g / min, carrier gas N2 flow rate 9L / min~10L / min; The atmospheric plasma spraying process parameters of the ceramic surface are: spraying angle of 90°~92°, spraying distance of 100mm~105mm, current of 400A~455A, power of 33kW~34kW, flow rate of working gas Ar gas of 41L / min~42L / min, flow rate of auxiliary gas H2 gas of 2.8L / min~3.8L / min, powder feeding amount of 38g / min~40g / min, and flow rate of carrier gas N2 gas of 9L / min~10L / min.

3. The method for preparing a high-entropy rare earth tantalate thermal protective coating by atmospheric plasma spraying according to claim 2, characterized in that: HE-RETaO4 powder for spraying is (Nd 0.2 Dy 0.2 Ho 0.2 Y 0.2 Er 0.2 )TaO4 powder is spray granulated and then heat treated to obtain spherical powder with a particle size of 30μm to 70μm.

4. The method for preparing a high-entropy rare earth tantalate thermal protective coating by atmospheric plasma spraying according to claim 3, characterized in that: The raw material composition of the spray granulation is as follows: based on the total mass of HE-RETaO4 powder and water as 100%, the mass fraction of HE-RETaO4 powder is 62% to 65%, and the balance is water; the amount of polyvinyl alcohol is 1.8% to 2% of the HE-RETaO4 powder; the amount of ammonium polyacrylate is 0.8% to 1% of the HE-RETaO4 powder; The spray granulation process parameters are: feed rate 45ml / min~50ml / min, atomization pressure 0.06MPa~0.08MPa, inlet temperature 230℃~240℃, outlet temperature 110℃~115℃; The heat treatment process parameters are as follows: the initial temperature is 25°C to 30°C, the temperature is increased to 600°C to 650°C at a heating rate of 5°C / min to 10°C / min, the temperature is kept constant for 3h to 3.5h, the temperature is then increased to 1100°C to 1150°C at a heating rate of 5°C / min to 10°C / min, the temperature is kept constant for 3h to 3.5h, and then the furnace is cooled; Before spraying, the HE-RETaO4 powder for spraying is dried at 90℃~100℃ and then placed in the powder feeding device.

5. A method for preparing a high entropy rare earth tantalate thermal protective coating by atmospheric plasma spraying according to any one of claims 1 to 4, characterized in that: In step (2), the atmospheric plasma spraying process parameters are: spraying angle of 90°~92°, spraying distance of 100mm~105mm, current of 380A~400A, power of 32kW~33kW, flow rate of working gas Ar gas of 42L / min~43L / min, flow rate of auxiliary gas H2 gas of 3.5L / min~4L / min, powder feeding amount of 38g / min~40g / min, and flow rate of carrier gas N2 gas of 8L / min~9L / min.

6. The method for preparing a high-entropy rare earth tantalate thermal protective coating by atmospheric plasma spraying according to claim 5, characterized in that: The particle size of the NiCrCoAlY powder is 30 μm to 100 μm. The powder is kept at 90° C. to 100° C. for 30 to 40 minutes and then placed in a powder feeding device for spraying.

7. The method for preparing a high-entropy rare earth tantalate thermal protective coating by atmospheric plasma spraying according to claim 1 or 2, characterized in that: The substrate is metal or alloy.

8. The method for preparing a high-entropy rare earth tantalate thermal protective coating by atmospheric plasma spraying according to claim 7, characterized in that: The substrate is a high-temperature nickel-based alloy.

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