Niobium alloy surface anti-oxidation composite coating as well as preparation method and application thereof

Abstract

The invention discloses a niobium alloy surface anti-oxidation composite coating and a preparation method and application thereof, and belongs to the technical field of coatings and preparation methods thereof. The anti-oxidation composite coating comprises a Cr-Si transition layer, and a compact Al-B-Y2O3 modified MoSi2 anti-oxidation layer and a YSZ heat insulation layer are sequentially arranged on the surface of the Cr-Si transition layer. The preparation method comprises the following steps that the surface of the base body is pretreated; preparing a Cr-Si transition layer on the surface of the matrix; an Al-B-Y2O3 modified MoSi2 anti-oxidation layer is prepared on the surface of the Cr-Si transition layer; and a YSZ heat insulation layer is sprayed on the surface of the Al-B-Y2O3 modified MoSi2 anti-oxidation layer. The invention provides a gradient composite coating which is high in interface bonding strength, capable of effectively blocking mutual diffusion of elements and excellent in oxidation resistance and heat insulation performance and a preparation method of the gradient composite coating.

Description

Technical Field

[0001] This invention relates to an anti-oxidation composite coating for niobium alloy surfaces, its preparation method, and its application, particularly to a coating for improving the anti-oxidation properties of niobium alloy surfaces, its preparation method, and its application, belonging to the field of coating and its preparation technology. Background Technology

[0002] Niobium alloys are promising high-temperature structural materials for aerospace applications due to their high melting point, good high-temperature strength, and machinability. However, niobium alloys suffer from catastrophic nitrogen embrittlement and severe oxidation in high-temperature (especially above 800°C) oxygen-containing environments, which severely limits their application in actual service environments.

[0003] To address this issue, a protective coating is typically applied to the niobium alloy surface. While common coating systems such as silicide coatings (e.g., NbSi2) offer some oxidation resistance, the difference in thermal expansion coefficients between the coating and the niobium alloy substrate leads to stress generation during thermal cycling, causing the coating to crack and peel off. Furthermore, at high temperatures, coating elements can interdiffuse with substrate elements, potentially causing substrate degradation or coating failure.

[0004] Furthermore, traditional silicide coatings primarily address oxidation resistance, but their thermal insulation capabilities are insufficient for the thermal barrier performance requirements of next-generation high thrust-to-weight ratio engines. Therefore, developing a multilayer composite coating that can firmly bond with the niobium alloy substrate, effectively prevent high-temperature oxidation, and possess significant thermal insulation properties is crucial for promoting the application of niobium alloys in ultra-high temperature environments. Summary of the Invention

[0005] Purpose of the invention: In order to overcome the shortcomings of the prior art, the purpose of this invention is to provide a niobium alloy surface anti-oxidation composite coating with long-lasting anti-oxidation properties, good thermal shock resistance, good heat insulation effect, and strong adhesion.

[0006] Another objective of this invention is to provide a method for preparing an anti-oxidation composite coating on a niobium alloy surface.

[0007] Another objective of this invention is to provide an application of an anti-oxidation composite coating on the surface of a niobium alloy. Technical solution

[0008] The present invention discloses an anti-oxidation composite coating for niobium alloy surface, comprising a Cr-Si transition layer, an Al-B-Y2O3 modified MoSi2 anti-oxidation layer, and a YSZ heat insulation layer. The modified MoSi2 anti-oxidation layer and the YSZ heat insulation layer are sequentially disposed on the surface of the Cr-Si transition layer. In the Cr-Si transition layer, the Si element increases in a gradient from the YSZ heat insulation layer to the modified MoSi2 anti-oxidation layer.

[0009] Furthermore, the thickness of the Cr-Si transition layer is 15-29 μm, the thickness of the modified MoSi2 antioxidant layer is 50-70 μm, and the thickness of the YSZ thermal insulation layer is 100-130 μm.

[0010] Furthermore, in the Cr-Si transition layer, the mass percentage of Nb is 75-80 wt%, the mass percentage of Cr is 10-15 wt%, and the balance is Si. The silicide diffusion layer formed by silicon infiltration on the surface of the niobium alloy substrate has a main phase composition of (Nb,X)Si2 (where X is an alloying element in the niobium alloy (C-103 niobium alloy is selected), such as Zr, Hf, Ti, etc.). This layer forms a metallurgical bond with the substrate through interdiffusion, exhibiting a gradient change in composition and a smooth transition in the coefficient of thermal expansion, greatly improving the adhesion between the coating and the substrate and alleviating thermal stress.

[0011] Furthermore, an Al-B-Y2O3 modified MoSi2 anti-oxidation layer is sprayed onto the Cr-Si transition layer. In this layer, silicon can form a dense SiO2 glass film at high temperatures, providing the main anti-oxidation capability. Al can preferentially oxidize over Si at high temperatures, forming a highly stable α-Al2O3 film. Moreover, Al2O3 and SiO2 can be mutually soluble to form a denser aluminosilicate glass with a lower oxygen diffusion rate, significantly improving the resistance to high-temperature oxidation. The oxidation product of B, B2O3, is liquid at 600-900°C, which can flow very quickly and heal microcracks in the coating in this temperature range, thereby suppressing the "Pesting" phenomenon. Rare earth element Y, as an "active element," can be enriched at the interface between SiO2 and the coating, significantly improving the adhesion of the oxide film and preventing it from peeling off during thermal cycling.

[0012] Furthermore, when spraying the modified MoSi2 antioxidant layer, the powder used is a core-shell composite powder. The core consists of Al powder (Al powder radius 4-8μm) and B4C powder (B4C powder radius 1-3μm). The Al powder and B4C powder are ball-milled (ball-to-powder ratio 10:1, ball milling speed 250-300rpm, ball milling time 5h) to form (Al-B4C) composite particles with a size of 5-15μm. The middle shell layer is formed by the sol-gel method (the mass of the Y2O3 shell layer accounts for 1.5-3.0wt.% of the composite core powder mass). Specifically, yttrium nitrate hexahydrate (Y(NO3)3·6H2O) is used as the precursor, and a mixed solvent of anhydrous ethanol (C2H5OH) and deionized water (volume ratio 4:1) is used as the solvent. Each treatment involves 50-100 [units of material]. (Al-B4C) composite powder, with a liquid-to-solid ratio (liquid volume mL: powder mass g) of 5:1 to 10:1. The ball-to-powder ratio is 10:1, the ball milling speed is 250-300 rpm, and the milling time is 5 hours. Deposition is guided by rotary evaporation for 1.5-3 hours at 40-50℃, followed by 2-3 hours of vacuum drying at at least 60℃. A layer of Y2O3 sol precursor is uniformly coated onto the (Al-B4C) core surface. After heat treatment (heating at 1-3℃ / min to 600-650℃, holding in argon for 1-3 hours, and then cooling with the furnace), a nanocrystalline Y2O3 shell is formed. The outermost shell layer is then deposited using chemical vapor deposition on the surface of the Y2O3-coated particles, forming the final complete core-shell spherical powder (particle size range 20-40 μm). In conventional mechanically mixed powders, low-melting-point Al and B4C evaporate or oxidize prematurely in plasma flames, leading to severe loss of effective components and a significant deviation between the actual and designed coating composition. However, in the core-shell structure of this invention, the MoSi2 outer shell melts first during spraying, becoming a protective carrier, encapsulating the internal (Al-B4C) core and Y2O3 intermediate layer, greatly reducing burn-off. Upon impact with the substrate, the outer shell breaks, releasing the core material and achieving in-situ synthesis and deposition. This ensures a high degree of precision and uniformity in the coating composition.

[0013] Furthermore, in the Al-B-Y2O3 modified MoSi2 antioxidant layer, the mass fraction of Al is 3-8 wt%, the mass fraction of B is 1-3 wt%, the mass fraction of Y2O3 is 0.5-2 wt%, and the balance is MoSi2.

[0014] In MoSi2, the mass percentage of Si is 25-30 wt%, the mass percentage of O is less than 1 wt%, and the balance is Mo.

[0015] Furthermore, the YSZ thermal insulation layer and the Al-B-Y2O3 modified MoSi2 antioxidant layer work synergistically to achieve a transition in composition, avoiding stress caused by different compositions and increasing the bonding force between the coatings. The Y2O3 layer is a typical thermal barrier coating ceramic layer with low thermal conductivity, which can effectively isolate heat from being transferred to the substrate.

[0016] The preparation method of the above-mentioned anti-oxidation composite coating on the surface of niobium alloy includes the following steps: Step 1: Pre-treat the substrate surface; Step 2: Prepare a Cr-Si transition layer on the substrate surface using a dual-glow plasma surface metallization method; Step 3: Prepare core-shell structured composite powder.

[0017] Step 4: The above-mentioned core-shell structure composite powder (i.e., MoSi2-Al-B4C-Y2O3 spherical core-shell structure composite powder) is sprayed using plasma spraying to prepare an Al-B-Y2O3 modified MoSi2 antioxidant layer on the surface of the Cr-Si transition layer. Step 5: Apply a YSZ heat insulation layer to the surface of the Al-B-Y2O3 modified MoSi2 antioxidant layer using plasma spraying.

[0018] Furthermore, in step one, the pretreatment involves sanding and polishing the substrate with sandpaper, followed by ultrasonic cleaning with ethanol and deionized water to remove grease and particulate contaminants.

[0019] Further, in step two, the process parameters of the double glow plasma surface metal infiltration method are: vacuum degree of 0.1-0.2 Pa, argon gas is introduced and kept at 35-40 Pa, workpiece cathode voltage of 500-600 V, source voltage of 1000-1100 V, temperature of 900-1000 ℃, and holding time of 2-3 h. Advantages of double glow plasma metal infiltration technology for preparing niobium alloy-Si gradient diffusion layer coating: (1) Fast diffusion rate. Due to the continuous bombardment of the workpiece by ions, the workpiece atoms are sputtered out, generating high-density dislocations and vacancies, forming diffusion channels for alloy elements, reducing diffusion activation energy, and accelerating the diffusion rate. (2) Achieve deep diffusion of Si elements, realize composition gradient distribution, and avoid interface abrupt changes. (3) Controllable coating thickness. The coating thickness can be controlled by adjusting voltage, current, gas pressure and holding time. (4) Utilize the plasma penetration effect to achieve metallurgical bonding between the coating and the substrate, which is strong and not easy to fall off.

[0020] Further, in step three, when preparing the core-shell composite powder, Al powder and B4C powder are first ball-milled at a mass ratio of 3:1. Then, the core powder is dispersed in a Y(NO3)3 alcohol solution. By controlling the hydrolysis-condensation process, a Y(OH)3 gel layer is formed on the particle surface. Subsequently, the temperature is raised to 600-650°C at 1-3°C / min and held in argon for 1-3 hours. Then, it is cooled in the furnace to transform into a nanocrystalline Y2O3 shell layer. Finally, the powder is placed in a CVD reactor and a mixed gas of MoCl5, SiHCl3 and H2 is introduced at 850-950°C (the volume ratio of MoCl5:SiHCl3:H2 is 1:(3.0-3.5):(30-50); the system pressure is 5-15 kPa, and the deposition time is 60-120 minutes) to uniformly deposit a dense MoSi2 layer on the particle surface, forming a complete core-shell structure.

[0021] Furthermore, in step four, an Al-B-Y2O3 modified MoSi2 antioxidant layer is sprayed onto the Cr-Si layer using plasma spraying. The plasma spraying powder is a core-shell structured spherical composite powder, the plasma gas is Ar, the power is 25-35kW, the spraying distance is 100-120mm, the powder feeding rate is 25-35g / min, and the spray gun moving speed is 500-700mm / s.

[0022] Further, in step five, a YSZ heat insulation layer is sprayed onto the modified MoSi2 layer using plasma spraying. The plasma spraying powder is: agglomerated sintered 8YSZ powder (high-purity nano-sized 8YSZ powder (average particle size approximately 50 nm, purity greater than 99%), deionized water, ammonium polyacrylate (dispersant, added at 0.5-1.0 wt.% of the YSZ powder mass), and polyvinyl alcohol (PVA) aqueous solution (binder, added at 2-4 wt.% of the YSZ powder mass; the mass concentration of the PVA aqueous solution is 5-8 wt.%). The material is ball-milled (using wet ball milling, with the following parameters: planetary ball mill or drum ball mill, grinding media being zirconia (YSZ) grinding balls, and grinding ball diameter using multi-gradation (e.g., Φ5mm, Φ10mm); ball-to-material ratio (grind ball mass: slurry mass): 2:1 to 3:1; ball mill revolution speed 200-300 rpm). The mixture is prepared by mixing at rpm (ball milling time is 24-48 hours) to form a stable and uniform slurry with a solid content of 35-45 wt.%. Spray granulation is then performed (using a centrifugal spray drying tower with an inlet temperature of 280-320℃ to ensure instantaneous drying of the droplet surface, forming a hard shell to prevent adhesion; the outlet temperature is 100-120℃, within which the solvent has been effectively evaporated, and the material temperature will not be too high to cause PVA decomposition or particle sintering; the atomizer speed is 10000-20000 rpm, and the high-speed rotating atomizing disc centrifugally pulverizes the slurry into tiny droplets, with the speed directly controlling the original droplet size; finally, hollow spherical agglomerates with good flowability are obtained, with the main particle size distribution in the target range of 45-90 μm, but containing a certain amount of fine powder). The powder is then sintered in air at a temperature of 1200-1300℃ for 1-2 hours, followed by natural cooling in the furnace. The sintered powder is then sieved using a standard sieve to select a particle size distribution of 45μm-100μm that meets the requirements for spraying. The plasma gas is Ar, the power is 35-45kW, the spraying distance is 120-150mm, the powder feeding rate is 30-40g / min, and the spray gun moving speed is 800-1000mm / s.

[0023] The present invention provides an anti-oxidation composite coating for niobium alloy surfaces. The coating has good adhesion to the substrate with a bonding strength of 60-66 MPa. After ablation at 2000℃ for 60 seconds, the coating still maintains its complete structure, with a linear ablation rate of only 0.027-0.037 mm / s.

[0024] This invention relates to the application of an anti-oxidation composite coating on a niobium alloy surface in high-temperature aerobic environments above 800°C. These environments include high thrust-to-weight ratio engines and high-temperature structural materials for aerospace applications.

[0025] Beneficial effects: Compared with the prior art, the present invention has the following significant features: This invention discloses an anti-oxidation composite coating for niobium alloy surfaces, its preparation method, and its application. The anti-oxidation composite coating includes a Cr-Si transition layer, on the surface of which a dense Al-B-Y₂O₃ modified MoSi₂ anti-oxidation layer and a YSZ heat insulation layer are sequentially disposed. In the Cr-Si transition layer, the Si element content increases in a gradient from the YSZ heat insulation layer towards the Al-B-Y₂O₃ modified MoSi₂ anti-oxidation layer. The preparation method includes the following steps: pretreating the substrate surface; preparing the Cr-Si transition layer on the substrate surface; preparing the Al-B-Y₂O₃ modified MoSi₂ anti-oxidation layer on the surface of the Cr-Si transition layer; and spraying the YSZ heat insulation layer onto the surface of the Al-B-Y₂O₃ modified MoSi₂ anti-oxidation layer. This invention provides a gradient composite coating with high interfacial bonding strength, effectively blocking element interdiffusion, and possessing excellent anti-oxidation and heat insulation properties, as well as its preparation method. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the structure of the present invention, wherein 1-Cr-Si transition layer, 2-Al-B-Y2O3 modified MoSi2 anti-oxidation layer, 3-YSZ heat insulation layer, and 4-niobium alloy matrix; Figure 2 This is a SEM image of the surface of the composite coating prepared in Example 1 of the present invention. Detailed Implementation

[0027] The following description, in conjunction with the accompanying drawings and embodiments of the present invention, will further clarify the objectives, technical solutions, and advantages of the present invention. The specific embodiments described are merely illustrative and are not intended to limit the scope of the invention.

[0028] Unless otherwise specified, all materials and reagents used in the following embodiments are commercially available. Experimental methods not specifically described in the embodiments are generally performed under standard conditions or as recommended by the manufacturer. Example 1

[0029] A method for preparing an anti-oxidation composite coating on a niobium alloy surface includes the following steps: S1. Grind and polish the blocky niobium alloy substrate 4 on 1200# sandpaper, and then ultrasonically clean it for 15 minutes each with ethanol and deionized water to remove grease and particulate contamination.

[0030] S2. The Cr-Si transition layer 1 is prepared by double glow plasma surface metallurgy. The niobium alloy substrate 4, Cr target and Si target are loaded into the double glow plasma surface metallurgy furnace. The niobium alloy substrate is the workpiece electrode and the target material is the source electrode. The mechanical pump is turned on to evacuate to a vacuum degree of 0.1 Pa. Argon gas is introduced and the argon gas pressure is maintained at 38 Pa during operation. The two-electrode power supply is turned on and the workpiece cathode voltage is set to 550 V, the source electrode voltage is set to 1050 V, the temperature is set to 950 ℃, and the temperature is maintained for 2.5 h.

[0031] S3. Preparation of core-shell composite powder: First, Al powder and B4C powder were ball-milled at a mass ratio of 3:1. Then, the core powder was dispersed in a Y(NO3)3 alcohol solution. The hydrolysis-condensation process was controlled (using yttrium nitrate hexahydrate (Y(NO3)3·6H2O) as the precursor, and a mixed solvent of anhydrous ethanol (C2H5OH) and deionized water (volume ratio 4:1) as the solvent). The mass of the Y2O3 shell accounted for 2.0 wt.% of the (Al-B4C) composite powder mass. Each treatment involved 80... The Al-B4C composite powder had a liquid-to-solid ratio (liquid volume mL: powder mass g) of 6:1. The ball-to-powder ratio was 10:1, the ball milling speed was 250 rpm, and the milling time was 5 h. Deposition was guided by rotary evaporation at 45 °C for 2 h, followed by 2.5 h of vacuum drying at 60 °C, forming a Y(OH)3 gel layer on the particle surface. The temperature was then increased to 650 °C at 2 °C / min and held for 2 h, followed by furnace cooling to transform it into a nanocrystalline Y2O3 shell. Finally, the powder was placed in a CVD reactor, and a mixed gas of MoCl5, SiHCl3, and H2 was introduced at 900 °C, with a MoCl5:SiHCl3:H2 volume ratio of 1:3.2:40. The system pressure was 10 kPa, and the deposition time was 90 min, resulting in a uniform and dense MoSi2 layer deposited on the particle surface, forming a complete core-shell structure.

[0032] S4. Apply an Al-B-Y2O3 modified MoSi2 layer 2 to the Cr-Si transition layer using plasma spraying. The spraying powder is the aforementioned core-shell structured composite spherical MoSi2 powder. The plasma gas is Ar, the power is 30kW, the spraying distance is 110mm, the powder feed rate is 30g / min, and the spray gun moving speed is 600mm / s.

[0033] S5. Finally, a YSZ thermal insulation layer 3 is sprayed onto the Al-B-Y2O3 modified MoSi2 layer 2 using plasma spraying. The plasma spraying powder is agglomerated sintered 8YSZ powder (high-purity nano-sized 8YSZ powder with an average particle size of approximately 50 μm). The powder was ball-milled with a solid content of 40 wt.% to prepare a stable and uniform slurry. The slurry consisted of a mixture of YSZ powder (n, purity greater than 99%), deionized water, ammonium polyacrylate (dispersant, added at 0.7 wt.% of the YSZ powder mass), and polyvinyl alcohol (PVA) aqueous solution (binder, added at 3 wt.% of the YSZ powder mass). Spray granulation was performed to obtain hollow spherical agglomerates with good flowability. The particle size distribution was mainly concentrated in the range of 45-90 μm. The agglomerates were then sintered in air at a temperature of 1250℃ for 1.5 hours. After that, the agglomerates were naturally cooled in the furnace. The sintered powder was then sieved using a standard sieve to select a particle size distribution of 45 μm-100 μm that met the requirements for spraying. The plasma gas was Ar, the power was 40 kW, the spraying distance was 130 mm, the powder feeding rate was 35 g / min, and the spray gun moving speed was 900 mm / s.

[0034] like Figure 1 As shown, the total thickness of the composite coating obtained in this embodiment is 195 μm, the thickness of the Cr-Si transition layer 1 is 20 μm, the thickness of the Al-B-Y2O3 modified MoSi2 antioxidant layer 2 is 60 μm, and the thickness of the YSZ heat insulation layer 3 is 115 μm.

[0035] In Cr-Si transition layer 1, the mass percentage of Nb is 78 wt%, the mass percentage of Cr is 13 wt%, and the balance is Si.

[0036] In the Al-B-Y2O3 modified MoSi2 antioxidant layer 2, the mass fraction of Al is 5wt%, the mass fraction of B is 2wt%, the mass fraction of Y2O3 is 1wt%, the mass percentage of Si is 25wt%, the mass percentage of O is 0.2wt%, and the balance is Mo.

[0037] like Figure 2 As shown, the composite coating prepared in this embodiment has a uniform and complete surface without obvious pores.

[0038] The coating obtained in this embodiment has good adhesion to the substrate, with a bonding strength of 65 MPa. After ablation at 2000℃ for 60 s, the coating still maintains its complete structure, and the linear ablation rate is only 0.032 mm / s.

[0039] This embodiment describes the application of an anti-oxidation composite coating on a niobium alloy surface in a high-temperature oxygen environment above 800°C. Such environments include high thrust-to-weight ratio engines and high-temperature structural materials for aerospace applications. Example 2

[0040] A method for preparing an anti-oxidation composite coating on a niobium alloy surface includes the following steps: S1. Grind and polish the blocky niobium alloy substrate 4 on 1200# sandpaper, and then ultrasonically clean it for 15 minutes each with ethanol and deionized water to remove grease and particulate contamination.

[0041] S2. The Cr-Si transition layer 1 is prepared by double glow plasma surface metallurgy. The niobium alloy substrate 4, Cr target and Si target are loaded into the double glow plasma surface metallurgy furnace. The substrate is the workpiece electrode and the target material is the source electrode. The mechanical pump is turned on to evacuate to a vacuum degree of 0.1 Pa. Argon gas is introduced and the argon gas pressure is maintained at 35 Pa during operation. The two-electrode power supply is turned on and the workpiece cathode voltage is set to 500 V, the source electrode voltage is set to 1000 V, the temperature is set to 900 ℃, and the temperature is maintained for 2 h.

[0042] S3. Preparation of core-shell composite powder: First, Al powder and B4C powder were ball-milled at a mass ratio of 3:1. Then, the core powder was dispersed in a Y(NO3)3 alcohol solution. The hydrolysis-condensation process was controlled (using yttrium nitrate hexahydrate (Y(NO3)3·6H2O) as the precursor, and a mixed solvent of anhydrous ethanol (C2H5OH) and deionized water (volume ratio 4:1) as the solvent). The mass of the Y2O3 shell accounted for 1.5 wt.% of the (Al-B4C) composite powder mass. Each treatment was performed on 50 samples. The Al-B4C composite powder was prepared with a liquid-to-solid ratio (liquid volume mL: powder mass g) of 5:1. The ball-to-powder ratio was 10:1, the ball milling speed was 300 rpm, and the milling time was 5 h. Deposition was guided by rotary evaporation at 40 °C for 1.5 h, followed by 2 h of vacuum drying at 65 °C, forming a Y(OH)3 gel layer on the particle surface. The temperature was then increased to 600 °C at 1 °C / min and held for 3 h, followed by furnace cooling to transform it into a nanocrystalline Y2O3 shell. Finally, the powder was placed in a CVD reactor, and a mixed gas of MoCl5, SiHCl3, and H2 was introduced at 850 °C, with a MoCl5:SiHCl3:H2 volume ratio of 1:3.0:30. The system pressure was 5 kPa, and the deposition time was 60 min, resulting in a uniform and dense MoSi2 layer deposited on the particle surface, forming a complete core-shell structure.

[0043] S4. A MoSi2 layer is sprayed onto the Cr-Si transition layer using plasma spraying. The spraying powder is a core-shell structured composite powder, the plasma gas is Ar, the power is 25kW, the spraying distance is 100mm, the powder feed rate is 25g / min, and the spray gun moving speed is 500mm / s.

[0044] S5. Finally, a YSZ insulation layer was sprayed onto the MoSi2 layer using plasma spraying. The plasma spraying powder was selected from agglomerated sintered 8YSZ powder (high-purity nano-sized 8YSZ powder (average particle size approximately 50 nm, purity greater than 99%), deionized water, ammonium polyacrylate (dispersant, added at 0.5 wt.% of the YSZ powder mass), and polyvinyl alcohol (PVA) aqueous solution (binder, added at 2 wt.% of the YSZ powder mass) were ball-milled to prepare a stable and uniform slurry with a solid content of 35 wt.%. Spray granulation was then performed to obtain hollow spherical agglomerates with good flowability, and the particle size distribution was mainly concentrated in the range of 45-90 nm. The powder was then sintered in air at a temperature of 1200℃ for 1 hour, followed by natural cooling in the furnace. The sintered powder was then sieved using a standard sieve to select a particle size distribution of 45μm-100μm that meets the requirements for spraying. The plasma gas was Ar, the power was 35kW, the spraying distance was 120mm, the powder feeding rate was 30g / min, and the spray gun moving speed was 800mm / s.

[0045] The total thickness of the composite coating obtained in this embodiment is 165 μm, the thickness of the Cr-Si transition layer 1 is 15 μm, the thickness of the modified MoSi2 antioxidant layer 2 is 50 μm, and the thickness of the YSZ heat insulation layer 3 is 100 μm. In the Cr-Si transition layer 1, the mass percentage of Nb is 80 wt%, the mass percentage of Cr is 15 wt%, and the balance is Si. In the Al-B-Y2O3 modified MoSi2 antioxidant layer 2, the mass percentage of Al is 3 wt%, the mass percentage of B is 1 wt%, the mass percentage of Y2O3 is 0.5 wt%, the mass percentage of Si is 28 wt%, the mass percentage of O is 1 wt%, and the balance is Mo.

[0046] The coating obtained in this embodiment has good adhesion to the substrate, with a bonding strength of 62 MPa. After ablation at 2000℃ for 60 s, the coating still maintains its complete structure, and the linear ablation rate is only 0.037 mm / s.

[0047] This embodiment describes the application of an anti-oxidation composite coating on a niobium alloy surface in a high-temperature oxygen environment above 800°C. Such environments include high thrust-to-weight ratio engines and high-temperature structural materials for aerospace applications. Example 3

[0048] A method for preparing an anti-oxidation composite coating on a niobium alloy surface includes the following steps: S1. Grind and polish the blocky niobium alloy substrate 4 on 1200# sandpaper, and then ultrasonically clean it for 15 minutes each with ethanol and deionized water to remove grease and particulate contamination.

[0049] S2. The Cr-Si transition layer 1 was prepared by a double glow plasma surface metallurgy method. The niobium alloy substrate 4, Cr target and Si target were loaded into the double glow plasma surface metallurgy furnace. The substrate was used as the workpiece electrode and the target material was used as the source electrode. The mechanical pump was turned on to evacuate to a vacuum of 0.2 Pa. Argon gas was introduced and the argon gas pressure was maintained at 36 Pa during operation. The two-electrode power supply was turned on and the workpiece cathode voltage was set to 580 V, the source electrode voltage was set to 1060 V, the temperature was set to 980 ℃, and the temperature was maintained for 2.5 h.

[0050] S3. Preparation of core-shell composite powder: First, Al powder and B4C powder were ball-milled at a mass ratio of 3:1. Then, the core powder was dispersed in a Y(NO3)3 alcohol solution. The hydrolysis-condensation process was controlled (using yttrium nitrate hexahydrate (Y(NO3)3·6H2O) as the precursor, and a mixed solvent of anhydrous ethanol (C2H5OH) and deionized water (volume ratio 4:1) as the solvent). The mass of the Y2O3 shell accounted for 3.0 wt.% of the (Al-B4C) composite powder mass. Each treatment involved 100... The Al-B4C composite powder was prepared with a liquid-to-solid ratio (liquid volume mL: powder mass g) of 10:1. The ball-to-powder ratio was 10:1, the ball milling speed was 300 rpm, and the milling time was 5 h. Deposition was guided by rotary evaporation at 50 °C for 3 h, followed by vacuum drying at 65 °C for 3 h, forming a Y(OH)3 gel layer on the particle surface. The temperature was then increased to 650 °C at 3 °C / min and held for 1 h, followed by furnace cooling to transform it into a nanocrystalline Y2O3 shell. Finally, the powder was placed in a CVD reactor, and a mixed gas of MoCl5, SiHCl3, and H2 was introduced at 950 °C, with a MoCl5:SiHCl3:H2 volume ratio of 1:3.5:50. The system pressure was 15 kPa, and the deposition time was 120 min, resulting in a uniform and dense MoSi2 layer deposited on the particle surface, forming a complete core-shell structure.

[0051] S4. A MoSi2 layer is sprayed onto the Cr-Si transition layer using plasma spraying. The spraying powder is a core-shell structured composite powder, the plasma gas is Ar, the power is 32kW, the spraying distance is 115mm, the powder feed rate is 30g / min, and the spray gun moving speed is 650mm / s.

[0052] S5. Finally, a YSZ insulation layer was sprayed onto the MoSi2 layer using plasma spraying. The plasma spraying powder was selected from agglomerated sintered 8YSZ powder (high-purity nano-sized 8YSZ powder (average particle size approximately 50 nm, purity greater than 99%), deionized water, ammonium polyacrylate (dispersant, added at 1.0 wt.% of the YSZ powder mass), and polyvinyl alcohol (PVA) aqueous solution (binder, added at 4 wt.% of the YSZ powder mass) were ball-milled to prepare a stable and uniform slurry with a solid content of 45 wt.%. Spray granulation was then performed to obtain hollow spherical agglomerates with good flowability, and the particle size distribution was mainly concentrated in the range of 45-90 nm. The powder was then sintered in air at a temperature of 1300℃ for 2 hours, followed by natural cooling in the furnace. The sintered powder was then sieved using a standard sieve to select a particle size distribution of 45μm-100μm that meets the requirements for spraying. The plasma gas was Ar, the power was 42kW, the spraying distance was 140mm, the powder feeding rate was 38g / min, and the spray gun moving speed was 850mm / s.

[0053] The total thickness of the composite coating obtained in this embodiment is 218 μm, the thickness of the Cr-Si transition layer 1 is 22 μm, the thickness of the modified MoSi2 antioxidant layer 2 is 70 μm, and the thickness of the YSZ heat insulation layer 3 is 126 μm.

[0054] In the Cr-Si transition layer 1, the mass percentage of Nb is 76 wt%, the mass percentage of Cr is 12 wt%, and the balance is Si. In the Al-B-Y2O3 modified MoSi2 antioxidant layer 2, the mass percentage of Al is 5 wt%, the mass percentage of B is 2 wt%, the mass percentage of Y2O3 is 1.5 wt%, the mass percentage of Si is 26 wt%, the mass percentage of O is 0.2 wt%, and the balance is Mo.

[0055] The coating obtained in this embodiment has good adhesion to the substrate, with a bonding strength of 60 MPa. After ablation at 2000℃ for 60 seconds, the coating still maintains its complete structure, and the linear ablation rate is only 0.035 mm / s.

[0056] This embodiment describes the application of an anti-oxidation composite coating on a niobium alloy surface in a high-temperature oxygen environment above 800°C. Such environments include high thrust-to-weight ratio engines and high-temperature structural materials for aerospace applications. Example 4

[0057] A method for preparing an anti-oxidation composite coating on a niobium alloy surface includes the following steps: S1. Grind and polish the blocky niobium alloy substrate 4 on 1200# sandpaper, and then ultrasonically clean it for 15 minutes each with ethanol and deionized water to remove grease and particulate contamination.

[0058] S2. The Cr-Si transition layer 1 is prepared by the double glow plasma surface metallurgy method. The niobium alloy substrate 4, Cr target and Si target are loaded into the double glow plasma surface metallurgy furnace. The substrate is the workpiece electrode and the target material is the source electrode. The mechanical pump is turned on to evacuate to a vacuum degree of 0.1 Pa. Argon gas is introduced and the argon gas pressure is maintained at 40 Pa during operation. The two-electrode power supply is turned on and the workpiece cathode voltage is set to 600 V, the source electrode voltage is set to 1100 V, the temperature is set to 1000 ℃, and the temperature is maintained for 3 h.

[0059] S3. Preparation of core-shell composite powder: First, Al powder and B4C powder were ball-milled at a mass ratio of 3:1. Then, the core powder was dispersed in a Y(NO3)3 alcohol solution. The hydrolysis-condensation process was controlled (using yttrium nitrate hexahydrate (Y(NO3)3·6H2O) as the precursor, and a mixed solvent of anhydrous ethanol (C2H5OH) and deionized water (volume ratio 4:1) as the solvent). The mass of the Y2O3 shell accounted for 2.0 wt.% of the (Al-B4C) composite powder mass. Each treatment was 90... The Al-B4C composite powder was prepared with a liquid-to-solid ratio (liquid volume mL: powder mass g) of 8:1. The ball-to-powder ratio was 10:1, the ball milling speed was 300 rpm, and the milling time was 5 h. Deposition was guided by rotary evaporation at 50 °C for 2 h, followed by vacuum drying at 60 °C for 2 h, forming a Y(OH)3 gel layer on the particle surface. The temperature was then increased to 600 °C at 2 °C / min and held for 2 h, followed by furnace cooling to transform it into a nanocrystalline Y2O3 shell. Finally, the powder was placed in a CVD reactor, and a mixed gas of MoCl5, SiHCl3, and H2 was introduced at 900 °C, with a MoCl5:SiHCl3:H2 volume ratio of 1:3.0:45. The system pressure was 12 kPa, and the deposition time was 100 min, resulting in a uniform and dense MoSi2 layer deposited on the particle surface, forming a complete core-shell structure.

[0060] S4. A MoSi2 layer is sprayed onto the Cr-Si transition layer using plasma spraying. The spraying powder is a core-shell structured composite powder, the plasma gas is Ar, the power is 35kW, the spraying distance is 120mm, the powder feed rate is 35g / min, and the spray gun moving speed is 700mm / s.

[0061] S5. Finally, a YSZ insulation layer was sprayed onto the MoSi2 layer using plasma spraying. The plasma spraying powder was selected from agglomerated sintered 8YSZ powder (high-purity nano-sized 8YSZ powder (average particle size approximately 50 nm, purity greater than 99%), deionized water, ammonium polyacrylate (dispersant, added at 0.6 wt.% of the YSZ powder mass), and polyvinyl alcohol (PVA) aqueous solution (binder, added at 2.8 wt.% of the YSZ powder mass) were ball-milled to prepare a stable and uniform slurry with a solid content of 42 wt.%. Spray granulation was then performed to obtain hollow spherical agglomerates with good flowability, and the particle size distribution was mainly concentrated in the range of 45-90 nm. The powder was then sintered in air at a temperature of 1200℃ for 1 hour, followed by natural cooling in the furnace. The sintered powder was then sieved using a standard sieve to select a particle size distribution of 45μm-100μm that meets the requirements for spraying. The plasma gas was Ar, the power was 45kW, the spraying distance was 150mm, the powder feeding rate was 40g / min, and the spray gun moving speed was 1000mm / s.

[0062] The total thickness of the composite coating obtained in this embodiment is 222 μm, the thickness of the Cr-Si transition layer 1 is 29 μm, the thickness of the modified MoSi2 antioxidant layer 2 is 63 μm, and the thickness of the YSZ heat insulation layer 3 is 130 μm.

[0063] In the Cr-Si transition layer 1, the mass percentage of Nb is 76 wt%, the mass percentage of Cr is 13 wt%, and the balance is Si. In the Al-B-Y₂O₃ modified MoSi₂ antioxidant layer 2, the mass percentage of Al is 6 wt%, the mass percentage of B is 2.4 wt%, the mass percentage of Y₂O₃ is 0.8 wt%, the mass percentage of Si is 26 wt%, the mass percentage of O is 0.3 wt%, and the balance is Mo.

[0064] The coating obtained in this embodiment has good adhesion to the substrate, with a bonding strength of 66 MPa. After ablation at 2000℃ for 60 s, the coating still maintains its complete structure, and the linear ablation rate is only 0.027 mm / s.

[0065] This embodiment describes the application of an anti-oxidation composite coating on a niobium alloy surface in a high-temperature oxygen environment above 800°C. Such environments include high thrust-to-weight ratio engines and high-temperature structural materials for aerospace applications. Example 5

[0066] A method for preparing an anti-oxidation composite coating on a niobium alloy surface includes the following steps: S1. Grind and polish the blocky niobium alloy substrate 4 on 1200# sandpaper, and then ultrasonically clean it for 15 minutes each with ethanol and deionized water to remove grease and particulate contamination.

[0067] S2. The Cr-Si transition layer 1 is prepared by double glow plasma surface metallurgy. The niobium alloy substrate 4, Cr target and Si target are loaded into the double glow plasma surface metallurgy furnace. The substrate is the workpiece electrode and the target material is the source electrode. The mechanical pump is turned on to evacuate to a vacuum degree of 0.2 Pa. Argon gas is introduced and the argon gas pressure is maintained at 39 Pa during operation. The two-electrode power supply is turned on and the workpiece cathode voltage is set to 540 V, the source electrode voltage is set to 1080 V, the temperature is set to 930 ℃, and the temperature is maintained for 3 h.

[0068] S3. Preparation of core-shell composite powder: First, Al powder and B4C powder were ball-milled at a mass ratio of 3:1. Then, the core powder was dispersed in a Y(NO3)3 alcohol solution. The hydrolysis-condensation process was controlled (using yttrium nitrate hexahydrate (Y(NO3)3·6H2O) as the precursor, and a mixed solvent of anhydrous ethanol (C2H5OH) and deionized water (volume ratio 4:1) as the solvent). The mass of the Y2O3 shell accounted for 2.5 wt.% of the (Al-B4C) composite powder mass. Each treatment consisted of 70... The Al-B4C composite powder had a liquid-to-solid ratio (liquid volume mL: powder mass g) of 9:1. The ball-to-powder ratio was 10:1, the ball milling speed was 300 rpm, and the ball milling time was 5 h. Deposition was guided by rotary evaporation at 45 °C for 2.5 h, followed by 3 h of vacuum drying at 60 °C, forming a Y(OH)3 gel layer on the particle surface. The temperature was then increased to 650 °C at 1 °C / min and held for 1 h, followed by furnace cooling to transform it into a nanocrystalline Y2O3 shell. Finally, the powder was placed in a CVD reactor, and a mixed gas of MoCl5, SiHCl3, and H2 was introduced at 880 °C, with a MoCl5:SiHCl3:H2 volume ratio of 1:3.0:50. The system pressure was 10 kPa, and the deposition time was 100 min, resulting in a uniform and dense MoSi2 layer deposited on the particle surface, forming a complete core-shell structure.

[0069] S4. A modified MoSi2 layer is sprayed onto the Cr-Si transition layer using plasma spraying. The spraying powder is a core-shell structured composite powder, the plasma gas is Ar, the power is 33kW, the spraying distance is 120mm, the powder feed rate is 35g / min, and the spray gun moving speed is 650mm / s.

[0070] S5. Finally, a YSZ insulation layer was sprayed onto the modified MoSi2 layer using plasma spraying. The plasma spraying powder was selected from agglomerated sintered 8YSZ powder (high-purity nano-sized 8YSZ powder (average particle size approximately 50 nm, purity greater than 99%), deionized water, ammonium polyacrylate (dispersant, added at 0.9 wt.% of the YSZ powder mass), and polyvinyl alcohol (PVA) aqueous solution (binder, added at 2.2 wt.% of the YSZ powder mass) and ball-milled to prepare a stable and uniform slurry with a solid content of 40 wt.%. Spray granulation was then performed to obtain hollow spherical agglomerates with good flowability, and the particle size distribution was mainly concentrated in the range of 45-90 nm. The powder was then sintered in air at a temperature of 1300℃ for 2 hours, followed by natural cooling in the furnace. The sintered powder was then sieved using a standard sieve to select a particle size distribution of 45μm-100μm that meets the requirements for spraying. The plasma gas was Ar, the power was 42kW, the spraying distance was 145mm, the powder feeding rate was 37g / min, and the spray gun moving speed was 920mm / s.

[0071] The total thickness of the composite coating obtained in this embodiment is 198 μm, the thickness of the Cr-Si transition layer 1 is 25 μm, the thickness of the Al-B-Y2O3 modified MoSi2 antioxidant layer 2 is 57 μm, and the thickness of the YSZ heat insulation layer 3 is 117 μm.

[0072] In the Cr-Si transition layer 1, the mass percentage of Nb is 75 wt%, the mass percentage of Cr is 10 wt%, and the balance is Si. In the Al-B-Y2O3 modified MoSi2 antioxidant layer 2, the mass percentage of Al is 8 wt%, the mass percentage of B is 3 wt%, the mass percentage of Y2O3 is 2 wt%, the mass percentage of Si is 30 wt%, the mass percentage of O is 0.1 wt%, and the balance is Mo.

[0073] The coating obtained in this embodiment has good adhesion to the substrate, with a bonding strength of 64 MPa. After ablation at 2000℃ for 60 s, the coating still maintains its complete structure, and the linear ablation rate is only 0.028 mm / s.

[0074] This embodiment describes the application of an anti-oxidation composite coating on a niobium alloy surface in a high-temperature oxygen environment above 800°C. Such environments include high thrust-to-weight ratio engines and high-temperature structural materials for aerospace applications.

[0075] Comparative Example 1

[0076] The remaining steps of this comparative example are the same as those of Example 1, except that the sprayed powder is a non-core-shell structured mechanically mixed MoSi2-5Al-2B4C-1Y2O3 (wt.%) spherical powder. The results showed that its bonding strength was only 45 MPa. After 60 seconds of oxyacetylene flame ablation at 2000℃, the coating completely disappeared, and the substrate was eroded into deep pits, with a linear ablation rate of 0.197 mm / s.

[0077] Comparative Example 2

[0078] The only difference between this comparative example and Example 1 is that: S3. Preparation of core-shell composite powder: First, Al powder and B4C powder were ball-milled at a mass ratio of 2:1 using high energy. Yttrium nitrate hexahydrate (Y(NO3)3·6H2O) was used as the precursor, and a mixed solvent of anhydrous ethanol (C2H5OH) and deionized water (volume ratio 4:1) was used as the solvent. The mass of the Y2O3 shell accounted for 1.0 wt.% of the mass of the composite core powder. Each processing yielded 40 g of (Al-B4C) composite powder, and the liquid-to-solid ratio (liquid volume mL: powder mass g) was 4:1. The ball-to-powder ratio was 10:1, the ball milling speed was 250 rpm, and the ball milling time was 5 h. At 35 °C, the particles were deposited by rotary evaporation for 4 h, followed by vacuum drying at 60 °C for 3 h to form a Y(OH)3 gel layer on the particle surface. Then, the temperature was increased to 650 °C at 2 °C / min and held for 2 h. After furnace cooling, the particles were transformed into nanocrystalline Y2O3 shells. Finally, the powder was placed in a CVD reactor and a mixed gas of MoCl5, SiHCl3 and H2 was introduced at 950 °C to uniformly deposit a dense MoSi2 layer on the particle surface, forming a complete core-shell structure.

[0079] The coating obtained in this comparative example has a bonding strength of only 40 MPa and a linear ablation rate of 0.182 mm / s.

[0080] Comparative Example 3

[0081] The only difference between this comparative example and Example 1 is that: S3. Preparation of core-shell composite powder: First, Al powder and B4C powder were ball-milled at a mass ratio of 4:1 using high energy. Yttrium nitrate hexahydrate (Y(NO3)3·6H2O) was used as the precursor, and a mixed solvent of anhydrous ethanol (C2H5OH) and deionized water (volume ratio 4:1) was used as the solvent. The mass of the Y2O3 shell accounted for 4.0 wt.% of the mass of the composite core powder. Each processing yielded 110 g of (Al-B4C) composite powder, and the liquid-to-solid ratio (liquid volume mL: powder mass g) was 12:1. The ball-to-particle ratio was 10:1, the ball milling speed was 300 rpm, and the ball milling time was 5 h. At 35 °C, the particles were deposited by rotary evaporation for 4 h, followed by vacuum drying at 60 °C for 3 h to form a Y(OH)3 gel layer on the particle surface. Then, the temperature was increased to 650 °C at 2 °C / min and held for 2 h. After furnace cooling, the particles were transformed into nanocrystalline Y2O3 shells. Finally, the powder was placed in a CVD reactor and a mixed gas of MoCl5, SiHCl3 and H2 was introduced at 950 °C to uniformly deposit a dense MoSi2 layer on the particle surface, forming a complete core-shell structure.

[0082] The coating obtained in this comparative example has a bonding strength of only 42 MPa and a linear ablation rate of 0.185 mm / s.

[0083] It should be understood that, in order to simplify this disclosure and aid in understanding one or more of the various aspects of the invention, features of the invention are sometimes grouped together in a single embodiment, figure, or description thereof in the above description of exemplary embodiments of the invention. However, this method of disclosure should not be interpreted as reflecting an intention that the claimed invention requires more features than expressly recited in each claim. Rather, as reflected in the claims, inventive aspects lie in fewer than all the features of the foregoingly disclosed embodiments. Therefore, the claims, following the detailed description, are hereby expressly incorporated into that detailed description, wherein each claim itself is a separate embodiment of the invention.

[0084] Although the invention has been described with reference to a limited number of embodiments, those skilled in the art will understand from the foregoing description that other embodiments are conceivable within the scope of the invention described herein. Furthermore, it should be noted that the language used in this specification has been chosen primarily for readability and instructional purposes, and not for the purpose of interpreting or limiting the subject matter of the invention. Therefore, many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the appended claims. The disclosure of the invention is illustrative and not restrictive, and the scope of the invention is defined by the appended claims.

[0085] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. An anti-oxidation composite coating for niobium alloy surfaces, characterized in that: From the inside out, it includes a Cr-Si transition layer, an Al-B-Y2O3 modified MoSi2 antioxidant layer, and a YSZ thermal insulation layer. In the Cr-Si transition layer, the Si element increases in a gradient from the YSZ thermal insulation layer to the modified MoSi2 antioxidant layer.

2. The anti-oxidation composite coating for niobium alloy surface according to claim 1, characterized in that: The thickness of the Cr-Si transition layer is 15-29 μm, the thickness of the Al-B-Y2O3 modified MoSi2 antioxidant layer is 50-70 μm, and the thickness of the YSZ thermal insulation layer is 100-130 μm.

3. The anti-oxidation composite coating for niobium alloy surface according to claim 1, characterized in that: In the Cr-Si transition layer, the mass percentage of Nb is 75~80wt%, the mass percentage of Cr is 10~15wt%, and the balance is Si.

4. The anti-oxidation composite coating for niobium alloy surface according to claim 1, characterized in that: In the Al-B-Y2O3 modified MoSi2 antioxidant layer, the mass fraction of Al is 3-8wt%, the mass fraction of B is 1-3wt%, the mass fraction of Y2O3 is 0.5-2wt%, and the balance is MoSi2. In MoSi2, the mass percentage of Si is 25-30 wt%, the mass percentage of O is less than 1 wt%, and the balance is Mo.

5. The anti-oxidation composite coating for niobium alloy surface according to claim 1, characterized in that: The coating has good adhesion to the substrate, with a bonding strength of 60-66 MPa. After ablation at 2000℃ for 60 seconds, the coating maintains its complete structure, with a linear ablation rate of 0.027-0.037 mm / s.

6. The application of the anti-oxidation composite coating on the surface of a niobium alloy according to any one of claims 1-5 in a high-temperature oxygen-containing environment above 800℃, characterized in that: High-temperature oxygen-rich environments above 800°C include high thrust-to-weight ratio engines and high-temperature structural materials for aerospace applications.

7. A method for preparing an anti-oxidation composite coating on a niobium alloy surface according to any one of claims 1-5, characterized in that: Includes the following steps: Step 1: Pre-treat the surface of the niobium alloy substrate; Step 2: Prepare a Cr-Si transition layer on the substrate surface using the double glow plasma surface metal infiltration method. The process of the double glow plasma surface metal infiltration method is as follows: vacuum degree is 0.1-0.2 Pa, argon gas is introduced and maintained at 35-40 Pa, cathode voltage of workpiece is 500-600 V, source voltage is 1000-1100 V, temperature is 900-1000 ℃, and holding time is 2-3 h. Step 3: Prepare core-shell structured composite powder; The core is composed of Al powder and B4C powder. Al powder and B4C powder are subjected to high-energy ball milling at a mass ratio of 3:1 to form (Al-B4C) composite particles with a size of 5-15 μm. The intermediate shell layer is formed by uniformly coating a Y2O3 sol precursor onto the surface of (Al-B4C) composite particles using a sol-gel method, followed by heat treatment to form a nanocrystalline Y2O3 shell layer. The outermost outer shell layer is obtained by chemical vapor deposition of a dense MoSi2 layer on the surface of the particles encased in the Y2O3 shell. Step 4: The above-mentioned core-shell structured composite powder is sprayed using plasma spraying to prepare an Al-B-Y2O3 modified MoSi2 antioxidant layer on the surface of the Cr-Si transition layer. The plasma spraying powder is a core-shell structured composite powder, the plasma gas is Ar, the power is 25-35kW, the spraying distance is 100-120mm, the powder feeding rate is 25-35g / min, and the spray gun moving speed is 500-700mm / s. Step 5: Apply a YSZ heat insulation layer to the surface of the Al-B-Y2O3 modified MoSi2 antioxidant layer using plasma spraying. The plasma spraying powder is agglomerated sintered 8YSZ powder, the plasma gas is Ar, the power is 35-45kW, the spraying distance is 120-150mm, the powder feeding rate is 30-40g / min, and the spray gun moving speed is 800-1000mm / s.

8. The preparation method according to claim 7, characterized in that: In step three, the high-energy ball milling process is as follows: the ball-to-material ratio is 10:1, the ball milling speed is 250-300 rpm, and the ball milling time is 5 hours. The sol-gel process is as follows: the mass of the Y2O3 shell accounts for 1.5-3.0 wt.% of the (Al-B4C) composite particles. Yttrium nitrate hexahydrate is used as a precursor, and a mixture of anhydrous ethanol and deionized water in a volume ratio of 4:1 is used as the solvent. Each treatment involves 50-100 g of (Al-B4C) composite particles with a liquid-to-solid ratio of 5:1 to 10:1 and a ball-to-particle ratio of 10:

1. The ball milling speed is 250-300 rpm, and the ball milling time is 5 h. Deposition is guided by rotary evaporation at 40-50℃ for 1.5-3 h, followed by vacuum drying at at least 60℃ for 2-3 h. The heat treatment process is as follows: heat up to 600-650℃ at a rate of 1-3℃ / min, hold in argon for 1-3 hours, and then cool with the furnace.

9. The preparation method according to claim 7, characterized in that: In step three, the chemical vapor deposition process is as follows: the particles coated with the Y2O3 shell are placed in a CVD reactor, and a mixed gas of MoCl5, SiHCl3 and H2 is introduced at 850-950°C. The volume ratio of MoCl5:SiHCl3:H2 is 1:(3.0-3.5):(30-50); the pressure is 5-15 kPa, and the deposition time is 60-120 minutes, so that a dense MoSi2 layer is uniformly deposited on the particle surface.

10. The preparation method according to claim 7, characterized in that: In step five, the preparation method of agglomerated sintered 8YSZ powder is as follows: nano-sized YSZ powder, deionized water, 0.5-1.0 wt.% of ammonium polyacrylate (APY) and 2-4 wt.% of polyvinyl alcohol (PVA) aqueous solution (PVA) are ball-milled and mixed to prepare a slurry with a solid content of 35-45 wt.% and a PVA aqueous solution concentration of 5-8 wt.%. Hollow spherical agglomerates are obtained by spray granulation, and then sintered in air at a temperature of 1200-1300℃ for 1-2 hours. After sintering, the powder is naturally cooled in the furnace, and the sintered powder is sieved to select powder with a particle size distribution of 45μm-100μm.

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