Niobium-silicon alloy surface high-temperature anti-oxidation coating and preparation method thereof

Abstract

The invention provides a niobium-silicon alloy surface high-temperature anti-oxidation coating and a preparation method thereof, and belongs to the technical field of material surface coatings. According to the invention, Nb, Ti, Si, Al, Hf and RE elements are used as material components to prepare the anti-oxidation coating, and the material components are similar to chemical components of a niobium-silicon alloy matrix, so that the anti-oxidation coating has good matrix compatibility; a continuous compact Al2O3 layer can be formed at a high temperature, and the niobium-silicon alloy has excellent high-temperature oxidation resistance, and pulverization oxidation of a niobium-silicon alloy matrix at the high temperature is avoided, so that high-temperature thermal protection of the niobium-silicon alloy is realized; the growth rate of Al2O3 is reduced through the rare earth element effect, the high-temperature oxidation resistance of the coating is further improved, the high-temperature service life of the oxidation-resistant coating is longer, the oxidation-resistant coating can continuously bear 800 h at the high temperature of 1300 DEG C, and the Al2O3 layer on the surface of the oxidation-resistant coating is not peeled off.

Description

Technical Field

[0001] This invention relates to the field of material surface coating technology, and in particular to a high-temperature anti-oxidation coating for niobium-silicon alloy surfaces and its preparation method. Background Technology

[0002] Nb-Si based superalloys have a lower density than Ni-based alloys (6.6~7.2 g / cm³). 3 With a liquidus temperature above 1900℃, as well as good high-temperature strength and room-temperature fracture toughness, Nb-Si based superalloys are expected to be used at temperatures between 1200~1400℃ or even higher, making them the most promising candidate material to replace Ni-based superalloys in aero-engines. However, Nb-Si based superalloys are prone to Pesting oxidation during high-temperature oxidation processes, failing to form a dense oxide protective film and exhibiting poor high-temperature oxidation resistance. Although numerous studies have shown that alloying with elements such as Cr, Al, Ti, B, Ge, and Hf can improve the high-temperature oxidation resistance of Nb-Si based alloys to some extent—for example, elements B and Ge can significantly inhibit Pesting oxidation of Nb-Si based alloys—these elements can also impair the mechanical properties of the alloy, such as room-temperature fracture toughness, high-temperature strength, and creep resistance.

[0003] Surface coating technology is an effective method to improve the oxidation resistance of Nb-Si based superalloys. Currently, the protective coatings for Nb-Si based alloys are mainly silicide coating systems (such as patents CN101200801A, CN118407001A, CN104561882A, CN116574990A, and CN107790730A). The surface oxide layer formed after high-temperature oxidation of the silicide coating is a composite oxide layer containing SiO2. For example, in a high-temperature oxidation environment, a dense amorphous borosilicate (B2O3-SiO2) oxide layer is formed on the surface of a Mo-Si-B coating. This oxide layer has good fluidity and self-healing ability, which can seal the pores and cracks generated during the oxidation process, thereby improving the oxidation resistance of the silicide coating. However, the silicide coating and the niobium alloy substrate are prone to interdiffusion at high temperatures, which can impair the mechanical properties of Nb-Si based superalloys. At the same time, the silicide coating is prone to softening at high temperatures and even significant volatilization at temperatures above 1650°C. In harsh service environments such as high stress, it is prone to peeling. These factors lead to premature failure of the silicide coating and seriously affect the service life of Nb-Si based superalloys in high-temperature environments.

[0004] Therefore, how to provide a coating that can improve the high-temperature oxidation resistance of niobium-silicon alloys has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] The purpose of this invention is to provide a high-temperature anti-oxidation coating for the surface of niobium-silicon alloy and its preparation method. The high-temperature anti-oxidation coating for the surface of niobium-silicon alloy provided by this invention can withstand a high temperature of 1300℃ for 800 hours continuously without peeling off the Al2O3 layer on the surface of the anti-oxidation coating.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a high-temperature anti-oxidation coating for the surface of niobium-silicon alloy, comprising the following components by atomic percentage: Nb: 12.5~13.4%; Ti: 20~25%; Si: 20~25%; Al: 34~38%; Hf: 3~6% and RE: 0.1~1%.

[0007] Preferably, the high-temperature anti-oxidation coating on the niobium-silicon alloy surface comprises the following components by atomic percentage: Nb: 12.5~13.4%; Ti: 23.5%; Si: 23.5%; Al: 36%; Hf: 3.5% and RE: 0.1~1%.

[0008] Preferably, the high-temperature anti-oxidation coating on the niobium-silicon alloy surface comprises the following components by atomic percentage: Nb: 13%; Ti: 23.5%; Si: 23.5%; Al: 36%; Hf: 3.5% and RE: 0.5%.

[0009] Preferably, the RE is Y or Dy.

[0010] This invention provides a method for preparing a high-temperature anti-oxidation coating on the surface of the niobium-silicon alloy as described above, comprising the following steps: (1) Alloy ingots are prepared by melting alloy raw materials; (2) The alloy ingot obtained in step (1) is crushed and ball-milled in sequence to obtain alloy powder; (3) Press the alloy powder obtained in step (2) to obtain a coating green blank, then combine the coating green blank with the niobium-silicon alloy substrate and sinter it, and finally perform homogenization heat treatment to obtain a high-temperature anti-oxidation coating on the surface of the niobium-silicon alloy.

[0011] Preferably, in step (2), the ball-to-material ratio of ball milling is (40~60):1, and the total ball milling time is 24~48h; the ball milling method is to mill in both forward and reverse directions for 5~20min each, then stop cooling for 30~50min, and repeat the process.

[0012] Preferably, the particle size of the alloy powder in step (2) is <20μm.

[0013] Preferably, the pressure applied in step (2) is 10~20MPa and the pressurization time is 1~3h.

[0014] Preferably, the sintering holding temperature in step (3) is 1100~1200℃, the sintering holding time is 5~10min, and the sintering pressure is 25~35MPa.

[0015] Preferably, in step (3), the holding temperature for homogenization heat treatment is 1200~1300℃, the holding time for homogenization heat treatment is 20~50h, and the vacuum degree for homogenization heat treatment is <10. -2 Pa.

[0016] This invention provides a high-temperature anti-oxidation coating for niobium-silicon alloy surfaces, comprising the following components by atomic percentage: Nb: 12.5~13.4%; Ti: 20~25%; Si: 20~25%; Al: 34~38%; Hf: 3~6% and RE: 0.1~1%. This invention uses Nb, Ti, Si, Al, Hf, and RE as material components, where RE is one of Y or Dy, to prepare an anti-oxidation coating. The material composition is similar to that of the niobium-silicon alloy substrate, exhibiting good substrate compatibility. Simultaneously, the coating can form a continuous and dense Al2O3 layer at high temperatures, possessing excellent high-temperature anti-oxidation performance, preventing the niobium-silicon alloy substrate from pulverizing and oxidizing at high temperatures, thus achieving high-temperature thermal protection for the niobium-silicon alloy. Furthermore, the rare earth element effect reduces the Al2O3 growth rate, further improving the high-temperature anti-oxidation performance of the coating and extending its high-temperature service life. The results of the embodiments show that the high-temperature anti-oxidation coating on the niobium-silicon alloy surface provided by the present invention does not peel off after being subjected to a high temperature of 1300℃ for 800 hours, and has excellent high-temperature oxidation resistance. Attached Figure Description

[0017] Figure 1 A cross-sectional scanning electron microscope image of the high-temperature anti-oxidation coating on the surface of the niobium-silicon alloy prepared in Example 1; Figure 2 XRD patterns of the high-temperature anti-oxidation coatings on the surface of the niobium-silicon alloys prepared in Examples 1-4; Figure 3 The image shows a cross-sectional scanning electron microscope (SEM) image of the high-temperature anti-oxidation coating on the surface of the niobium-silicon alloy prepared in Example 1 after oxidation at 1300°C for 800 hours. Figure 4 Cross-sectional scanning electron microscope and elemental distribution map of the high-temperature anti-oxidation coating on the surface of the niobium-silicon alloy prepared in Example 1 after oxidation at 1300℃ for 800h; Figure 5 This is a cross-sectional scanning electron microscope image of the high-temperature anti-oxidation coating on the surface of the niobium-silicon alloy prepared in Example 2 after oxidation at 1300℃ for 800 hours. Figure 6The image shows a cross-sectional scanning electron microscope (SEM) image of the high-temperature anti-oxidation coating on the surface of the niobium-silicon alloy prepared in Example 3 after oxidation at 1300°C for 800 hours. Figure 7 This is a cross-sectional scanning electron microscope image of the high-temperature anti-oxidation coating on the surface of the niobium-silicon alloy prepared in Example 4 after oxidation at 1300℃ for 800 hours. Figure 8 A cross-sectional scanning electron microscope image of the niobium-silicon alloy substrate provided for Comparative Example 1 after oxidation at 1300℃ for 96 hours; Figure 9 The image shows a cross-sectional scanning electron microscope (SEM) image of the niobium-silicon alloy surface coating prepared for Comparative Example 2 after oxidation at 1300℃ for 500 hours. Detailed Implementation

[0018] This invention provides a high-temperature anti-oxidation coating for the surface of niobium-silicon alloy, comprising the following components by atomic percentage: Nb: 12.5~13.4%; Ti: 20~25%; Si: 20~25%; Al: 34~38%; Hf: 3~6% and RE: 0.1~1%.

[0019] The high-temperature anti-oxidation coating on the surface of the niobium-silicon alloy provided by this invention comprises Nb: 12.5~13.4% by atomic percentage. As one embodiment of this invention, the atomic percentage of Nb can be 12.5%, 12.6%, 12.7%, 12.8%, 12.9%, 13%, 13.1%, 13.2%, 13.3%, or 13.4%. By adding Nb to the coating and controlling its amount, this invention can make its composition very close to that of the niobium-silicon alloy, thus achieving good matrix compatibility. Simultaneously, it can form a niobium silicide framework, providing a structural basis and high-temperature strength, while also adjusting the toughness and brittleness of the coating.

[0020] The high-temperature anti-oxidation coating on the surface of the niobium-silicon alloy provided by this invention comprises Ti: 20-25% by atomic percentage. As one embodiment of this invention, the atomic percentage of Ti can be 20%, 20.5%, 21%, 21.5%, 22%, 22.5%, 23%, 23.5%, 24%, 24.5%, or 25%. By adding Ti to the coating and controlling its amount, this invention can make its composition very close to that of the niobium-silicon alloy, thus achieving good matrix compatibility. Simultaneously, Ti can significantly improve the toughness and plasticity of the coating, promote the formation of a protective oxide film, refine the microstructure, and stabilize beneficial phases.

[0021] The high-temperature anti-oxidation coating on the surface of the niobium-silicon alloy provided by this invention comprises 20-25% Si by atomic percentage. As one embodiment of this invention, the atomic percentage of Si can be 20%, 20.5%, 21%, 21.5%, 22%, 22.5%, 23%, 23.5%, 24%, 24.5%, or 25%. By adding Si to the coating and controlling its amount, this invention can make its composition very close to that of the niobium-silicon alloy, thereby achieving good matrix compatibility and simultaneously generating a niobium silicide framework to provide high-temperature structural strength.

[0022] The high-temperature anti-oxidation coating on the surface of the niobium-silicon alloy provided by this invention comprises Al: 34~38% by atomic percentage. As one embodiment of this invention, the atomic percentage of Al can be 34%, 34.5%, 35%, 35.5%, 36%, 36.5%, 37%, 37.5%, or 38%. By adding Al to the coating and controlling its amount, this invention can form a continuous and dense Al2O3 layer at high temperatures. The Al2O3 layer possesses excellent high-temperature anti-oxidation properties, preventing the niobium-silicon alloy substrate from oxidizing at high temperatures.

[0023] The high-temperature anti-oxidation coating on the surface of the niobium-silicon alloy provided by this invention comprises Hf: 3~6% by atomic percentage. As one embodiment of this invention, the atomic percentage of Hf can be 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, or 6%. By adding Hf to the coating and controlling its amount, this invention can make its composition very close to that of the niobium-silicon alloy, thereby achieving good matrix compatibility. Simultaneously, it can improve the adhesion of the Al2O3 protective film, prevent its premature failure, inhibit pest oxidation (catastrophic oxidation), reduce the oxidation rate, and promote the formation of a protective oxide film.

[0024] The high-temperature anti-oxidation coating on the niobium-silicon alloy surface provided by this invention comprises RE: 0.1~1% by atomic percentage; the RE is preferably Y or Dy. As one embodiment of this invention, the atomic percentage of the RE can be 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, or 1%. This invention, by adding RE elements to the coating and controlling its dosage, reduces the Al2O3 growth rate through the rare earth element effect, further improving the high-temperature anti-oxidation performance of the coating, resulting in a longer high-temperature service life. It can continuously withstand a high temperature of 1300℃ for 800 hours without peeling off the Al2O3 layer on the surface of the anti-oxidation coating.

[0025] In this invention, the thickness of the high-temperature anti-oxidation coating on the niobium-silicon alloy surface is preferably 100~300μm. As one embodiment of this invention, the thickness of the high-temperature anti-oxidation coating on the niobium-silicon alloy surface can be 100μm, 150μm, 200μm, 250μm, or 300μm.

[0026] This invention prepares an anti-oxidation coating using Nb, Ti, Si, Al, Hf, and RE elements as material components, where RE is one of Y and Dy. The material composition is similar to the chemical composition of the niobium-silicon alloy substrate, exhibiting good substrate compatibility. By adding Al to the anti-oxidation coating, a continuous and dense Al2O3 layer can be formed at high temperatures, possessing excellent high-temperature anti-oxidation performance (thermodynamic stability), preventing the niobium-silicon alloy substrate from pulverizing and oxidizing at high temperatures, thereby achieving high-temperature thermal protection for the niobium-silicon alloy. The rare earth element effect reduces the Al2O3 growth rate, further improving the high-temperature anti-oxidation performance of the coating, resulting in a longer high-temperature service life. It can withstand continuous high temperatures of 1300℃ for 800 hours without peeling off the Al2O3 layer on the surface of the anti-oxidation coating.

[0027] This invention also provides a method for preparing the high-temperature anti-oxidation coating on the surface of the niobium-silicon alloy described in the above technical solution, comprising the following steps: (1) Alloy ingots are prepared by melting alloy raw materials; (2) The alloy ingot obtained in step (1) is crushed and ball-milled in sequence to obtain alloy powder; (3) Press the alloy powder obtained in step (2) to obtain a coating green blank, then combine the coating green blank with the niobium-silicon alloy substrate and sinter it, and finally perform homogenization heat treatment to obtain a high-temperature anti-oxidation coating on the surface of the niobium-silicon alloy.

[0028] This invention prepares alloy ingots by melting alloy raw materials.

[0029] The present invention does not impose any special limitations on the specific type, amount and source of the alloy raw materials. Based on the technical common sense of those skilled in the art, it is sufficient to ensure that the atomic percentage content of the elements in the anti-oxidation coating meets the requirements.

[0030] In this invention, the melting process is preferably non-consumable vacuum arc melting. This invention does not impose specific limitations on the melting parameters; the specific operations and parameters for melting can be determined based on the technical knowledge of those skilled in the art, as long as the components are mixed uniformly.

[0031] After obtaining the alloy ingot, the present invention crushes and ball-mills the alloy ingot sequentially to obtain alloy powder.

[0032] The present invention does not have any special limitations on the specific crushing operation. Based on the technical common sense of those skilled in the art, it can be determined that the alloy ingot can be crushed to a level that is suitable for ball milling.

[0033] In this invention, the preferred ball-to-powder ratio for ball milling is (40~60):1; the preferred total ball milling time is 24~48 hours; the preferred ball milling method is to mill in both forward and reverse directions for 5~20 minutes each, then stop cooling for 30~50 minutes, and repeat the process; the preferred material for the milling jar and milling balls is tungsten steel. As one embodiment of this invention, the ball-to-powder ratio for ball milling can be 40:1, 45:1, 50:1, 55:1, or 60:1; the preferred total ball milling time can be 24 hours, 28 hours, 32 hours, 36 hours, 40 hours, 44 hours, or 48 hours; the preferred ball milling method is to mill in both forward and reverse directions for 10~15 minutes each, then stop cooling for 35~40 minutes, and repeat the process. This invention, by controlling the parameters during the ball milling process, can ensure that the particle size of the alloy powder meets the requirements.

[0034] In this invention, the particle size of the alloy powder is preferably <20 μm. By controlling the particle size of the alloy powder, this invention facilitates the improvement of the density of the coating green body during subsequent preparation.

[0035] After obtaining the alloy powder, the present invention pressurizes the alloy powder to obtain a coating green blank, then combines the coating green blank with the niobium-silicon alloy substrate and sinters, and finally performs homogenization heat treatment to obtain a high-temperature anti-oxidation coating on the surface of the niobium-silicon alloy.

[0036] In this invention, the pressure applied is preferably 10-20 MPa; the pressurization time is preferably 1-3 hours; the pressurization process is preferably as follows: alloy powder is placed in a stainless steel powder pressing mold, and then pressurized using a hydraulic press; the inner diameter of the stainless steel powder pressing mold is preferably the same as the inner diameter of the graphite mold used during sintering. As one embodiment of this invention, the pressure applied can be 10 MPa, 12 MPa, 15 MPa, 18 MPa, or 20 MPa; the pressurization time can be 1 hour, 1.5 hours, 2 hours, 2.5 hours, or 3 hours. This invention improves the density of the coated green body through pressurization.

[0037] In this invention, the thickness of the coated green blank is preferably ≥1 mm. By controlling the thickness of the coated green blank, this invention can ensure that a sufficiently thick anti-oxidation coating is formed on the surface of the niobium-silicon superalloy.

[0038] This invention does not impose any specific limitations on the composition of the niobium-silicon alloy matrix; any commercially available niobium-silicon high-temperature alloy matrix well-known to those skilled in the art can be used. As one embodiment of this invention, the composition of the niobium-silicon alloy matrix can be Nb-26Ti-16Si-8Hf-3Al.

[0039] In this invention, the preferred method for combining the coated green blank and the niobium-silicon alloy substrate is as follows: cubic boron nitride is sprayed onto the inner surface of the mold sleeve and the pressure head of the graphite mold using a boron nitride cold spray agent and dried. After the coated green blank and the niobium-silicon alloy substrate are bonded together, a high-purity tantalum sheet is placed on one side of the coated green blank, and another high-purity tantalum sheet is placed on the other side away from the coated green blank. Then, the mold is placed inside the graphite mold. The purity of the high-purity tantalum sheet is preferably >99.99%. This invention prevents the mold from sticking to the product by spraying cubic boron nitride, thus improving surface quality. The placement of the high-purity tantalum sheet avoids the problem of carbon diffusion from the mold into the coated green blank during sintering, which could affect the coating composition and performance.

[0040] In this invention, the sintering method is preferably spark plasma sintering; the holding temperature of the sintering is preferably 1100~1200℃; the holding time of the sintering is preferably 5~10min; the heating rate to the holding temperature of the sintering is preferably 80~120℃ / min; the sintering pressure is preferably 25~35MPa; and the cooling method after sintering is preferably furnace cooling. In one embodiment of the present invention, the sintering holding temperature can be 1100℃, 1120℃, 1150℃, 1180℃, or 1200℃; the sintering holding time can be 5 min, 6 min, 7 min, 8 min, 9 min, or 10 min; the heating rate to the sintering holding temperature can be 80℃ / min, 85℃ / min, 90℃ / min, 95℃ / min, 100℃ / min, 105℃ / min, 110℃ / min, 115℃ / min, or 120℃ / min; and the sintering pressure can be 25 MPa, 28 MPa, 30 MPa, 32 MPa, or 35 MPa. By controlling the sintering parameters, the present invention can significantly improve the density of the coating, thereby further improving the performance of the coating.

[0041] The present invention preferably also includes removing the high-purity tantalum sheet after sintering. The present invention does not have specific limitations on the specific operation for removing the high-purity tantalum sheet; simply peeling off the high-purity tantalum sheet is sufficient. Removing the high-purity tantalum sheet in this invention can prevent it from affecting the homogenization heat treatment.

[0042] In this invention, the holding temperature for the homogenization heat treatment is preferably 1200~1300℃; the holding time for the homogenization heat treatment is preferably 20~50h; the heating rate to the homogenization heat treatment holding temperature is preferably 3~5℃ / min; and the vacuum degree of the homogenization heat treatment is preferably <10. -2 Pa; the cooling rate after the homogenization heat treatment is preferably 2~3℃ / min. As one embodiment of the invention, the holding temperature for the homogenization heat treatment can be 1200℃, 1220℃, 1250℃, 1280℃, or 1300℃; the holding time for the homogenization heat treatment can be 20h, 25h, 30h, 35h, 40h, 45h, or 50h. The present invention, through homogenization heat treatment, can form a uniform and dense coating. After high-temperature oxidation, a dense Al2O3 oxide layer is formed on the coating surface, providing excellent high-temperature oxidation resistance for niobium-silicon high-temperature alloys.

[0043] This invention employs a composite preparation process of melting ball milling powder preparation + spark plasma sintering + homogenization heat treatment, which ensures no pollution during the preparation process and that the prepared coating has a uniform and controllable microstructure and composition.

[0044] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0045] Example 1 A high-temperature anti-oxidation coating for a niobium-silicon alloy surface, comprising the following components by atomic percentage: Nb: 13%; Ti: 23.5%; Si: 23.5%; Al: 36%; Hf: 3.5% and RE: 0.5%; wherein RE is Dy; The method for preparing the high-temperature anti-oxidation coating on the surface of the niobium-silicon alloy comprises the following steps: (1) The alloy raw materials with the above composition are used to prepare alloy ingots by non-consumable vacuum arc melting; (2) The alloy ingot obtained in step (1) is crushed and ball-milled in sequence to obtain alloy powder with a particle size of <20μm; the ball-to-material ratio of the ball milling is 40:1, the total ball milling time is 48h, the ball milling method is to ball mill in both forward and reverse directions for 10min each, and then stop cooling for 40min, and repeat the process; the ball milling jar and grinding balls used in the ball milling are made of tungsten steel. (3) The alloy powder obtained in step (2) is placed into a stainless steel powder pressing mold and pressed using a hydraulic press to obtain a coated green blank with a thickness of 1 mm. Cubic boron nitride is sprayed onto the inner surface of the mold sleeve and the press head of the graphite mold using boron nitride cold spraying agent and dried for 24 h. After the coated green blank and the niobium-silicon alloy substrate (the composition of the niobium-silicon alloy substrate is Nb-26Ti-16Si-8Hf-3Al) are bonded together, a high-purity tantalum sheet is placed on one side of the coated green blank, and another high-purity tantalum sheet is placed on the other side away from the coated green blank. Then it is placed into the graphite mold for sintering. After that, it is cooled with the furnace, the high-purity tantalum sheet is peeled off, and finally a homogenization heat treatment is performed to obtain a high-temperature anti-oxidation coating on the surface of the niobium-silicon alloy. The pressurization pressure is 20 MPa, and the pressurization time is 1 hour; the purity of the high-purity tantalum sheet is >99.99%; the inner diameter of the stainless steel powder pressing mold is the same as the inner diameter of the graphite mold used during sintering; the sintering method is spark plasma sintering, the sintering holding temperature is 1150℃, the sintering holding time is 5 minutes, the heating rate to the sintering holding temperature is 100℃ / min, and the sintering pressure is 30 MPa; the homogenization heat treatment holding temperature is 1300℃, the homogenization heat treatment holding time is 24 hours, the heating rate to the homogenization heat treatment holding temperature is 3℃ / min, and the vacuum degree of the homogenization heat treatment is <10. -2 Pa; the cooling rate after the homogenization heat treatment is 3℃ / min.

[0046] Example 2 A high-temperature anti-oxidation coating for a niobium-silicon alloy surface comprises, by atomic percentage, the following components: Nb: 13.4%; Ti: 23.5%; Si: 23.5%; Al: 36%; Hf: 3.5% and RE: 0.1%; wherein RE is Dy; The method for preparing the high-temperature anti-oxidation coating on the surface of the niobium-silicon alloy comprises the following steps: (1) The alloy raw materials with the above composition are used to prepare alloy ingots by non-consumable vacuum arc melting; (2) The alloy ingot obtained in step (1) is crushed and ball-milled in sequence to obtain alloy powder with a particle size of <20μm; the ball-to-material ratio of the ball milling is 50:1, the total ball milling time is 48h, the ball milling method is to ball mill in both forward and reverse directions for 10min each, and then stop cooling for 40min, and repeat the process; the ball milling jar and grinding balls used in the ball milling are made of tungsten steel. (3) The alloy powder obtained in step (2) is placed into a stainless steel powder pressing mold and pressed using a hydraulic press to obtain a coated green blank with a thickness of 1 mm. Cubic boron nitride is sprayed onto the inner surface of the mold sleeve and the press head of the graphite mold using boron nitride cold spraying agent and dried for 24 h. After the coated green blank and the niobium-silicon alloy substrate (the composition of the niobium-silicon alloy substrate is Nb-26Ti-16Si-8Hf-3Al) are bonded together, a high-purity tantalum sheet is placed on one side of the coated green blank, and another high-purity tantalum sheet is placed on the other side away from the coated green blank. Then it is placed into the graphite mold for sintering. After that, it is cooled with the furnace, the high-purity tantalum sheet is peeled off, and finally a homogenization heat treatment is performed to obtain a high-temperature anti-oxidation coating on the surface of the niobium-silicon alloy. The pressurization pressure is 20 MPa, and the pressurization time is 1 hour; the purity of the high-purity tantalum sheet is >99.99%; the inner diameter of the stainless steel powder pressing mold is the same as the inner diameter of the graphite mold used during sintering; the sintering method is spark plasma sintering, the sintering holding temperature is 1150℃, the sintering holding time is 5 minutes, the heating rate to the sintering holding temperature is 100℃ / min, and the sintering pressure is 30 MPa; the homogenization heat treatment holding temperature is 1300℃, the homogenization heat treatment holding time is 24 hours, the heating rate to the homogenization heat treatment holding temperature is 3℃ / min, and the vacuum degree of the homogenization heat treatment is <10. -2 Pa; the cooling rate after the homogenization heat treatment is 3℃ / min.

[0047] Example 3 A high-temperature anti-oxidation coating for a niobium-silicon alloy surface, comprising the following components by atomic percentage: Nb: 12.5%; Ti: 23.5%; Si: 23.5%; Al: 36%; Hf: 3.5% and RE: 1%; wherein RE is Dy; The method for preparing the high-temperature anti-oxidation coating on the surface of the niobium-silicon alloy comprises the following steps: (1) The alloy raw materials with the above composition are used to prepare alloy ingots by non-consumable vacuum arc melting; (2) The alloy ingot obtained in step (1) is crushed and ball-milled in sequence to obtain alloy powder with a particle size of <20μm; the ball-to-material ratio of the ball milling is 60:1, the total ball milling time is 48h, the ball milling method is to ball mill in both forward and reverse directions for 10min each, and then stop cooling for 40min, and repeat the process; the ball milling jar and grinding balls used in the ball milling are made of tungsten steel. (3) The alloy powder obtained in step (2) is placed into a stainless steel powder pressing mold and pressed using a hydraulic press to obtain a coated green blank with a thickness of 1 mm. Cubic boron nitride is sprayed onto the inner surface of the mold sleeve and the press head of the graphite mold using boron nitride cold spraying agent and dried for 24 h. After the coated green blank and the niobium-silicon alloy substrate (the composition of the niobium-silicon alloy substrate is Nb-26Ti-16Si-8Hf-3Al) are bonded together, a high-purity tantalum sheet is placed on one side of the coated green blank, and another high-purity tantalum sheet is placed on the other side away from the coated green blank. Then it is placed into the graphite mold for sintering. After that, it is cooled with the furnace, the high-purity tantalum sheet is peeled off, and finally a homogenization heat treatment is performed to obtain a high-temperature anti-oxidation coating on the surface of the niobium-silicon alloy. The pressurization pressure is 20 MPa, and the pressurization time is 1 hour; the purity of the high-purity tantalum sheet is >99.99%; the inner diameter of the stainless steel powder pressing mold is the same as the inner diameter of the graphite mold used during sintering; the sintering method is spark plasma sintering, the sintering holding temperature is 1200℃, the sintering holding time is 6 minutes, the heating rate to the sintering holding temperature is 120℃ / min, and the sintering pressure is 30 MPa; the homogenization heat treatment holding temperature is 1300℃, the homogenization heat treatment holding time is 30 hours, the heating rate to the homogenization heat treatment holding temperature is 3℃ / min, and the vacuum degree of the homogenization heat treatment is <10. -2 Pa; the cooling rate after the homogenization heat treatment is 3℃ / min.

[0048] Example 4 A high-temperature anti-oxidation coating for a niobium-silicon alloy surface, comprising the following components by atomic percentage: Nb: 13%; Ti: 23.5%; Si: 23.5%; Al: 36%; Hf: 3.5% and RE: 0.5%; wherein RE is Y. The method for preparing the high-temperature anti-oxidation coating on the surface of the niobium-silicon alloy comprises the following steps: (1) The alloy raw materials with the above composition are used to prepare alloy ingots by non-consumable vacuum arc melting; (2) The alloy ingot obtained in step (1) is crushed and ball-milled in sequence to obtain alloy powder with a particle size of <20μm; the ball-to-material ratio of the ball milling is 50:1, the total ball milling time is 40h, the ball milling method is to ball mill in both forward and reverse directions for 10min each, and then stop cooling for 40min, and repeat the process; the ball milling jar and grinding balls used in the ball milling are made of tungsten steel. (3) The alloy powder obtained in step (2) is placed into a stainless steel powder pressing mold and pressed using a hydraulic press to obtain a coated green blank with a thickness of 1 mm. Cubic boron nitride is sprayed onto the inner surface of the mold sleeve and the press head of the graphite mold using boron nitride cold spraying agent and dried for 24 h. After the coated green blank and the niobium-silicon alloy substrate (the composition of the niobium-silicon alloy substrate is Nb-26Ti-16Si-8Hf-3Al) are bonded together, a high-purity tantalum sheet is placed on one side of the coated green blank, and another high-purity tantalum sheet is placed on the other side away from the coated green blank. Then it is placed into the graphite mold for sintering. After that, it is cooled with the furnace, the high-purity tantalum sheet is peeled off, and finally a homogenization heat treatment is performed to obtain a high-temperature anti-oxidation coating on the surface of the niobium-silicon alloy. The structure consists of three layers; the pressurization pressure is 20 MPa, and the pressurization time is 1 hour; the purity of the high-purity tantalum sheet is >99.99%; the inner diameter of the stainless steel powder pressing mold is the same as the inner diameter of the graphite mold used during sintering; the sintering method is spark plasma sintering, the sintering holding temperature is 1100℃, the sintering holding time is 8 minutes, the heating rate to the sintering holding temperature is 80℃ / min, and the sintering pressure is 30 MPa; the homogenization heat treatment holding temperature is 1250℃, the homogenization heat treatment holding time is 30 hours, the heating rate to the homogenization heat treatment holding temperature is 3℃ / min, and the vacuum degree of the homogenization heat treatment is <10. -2 Pa; the cooling rate after the homogenization heat treatment is 3℃ / min.

[0049] Cross-sectional scanning electron microscope image of the high-temperature anti-oxidation coating on the niobium-silicon alloy surface prepared in Example 1 is shown below. Figure 1 As shown. By Figure 1 It can be seen that the thickness of the high-temperature anti-oxidation coating on the surface of the niobium-silicon alloy prepared by the present invention is about 200 μm, and it is tightly bonded to the niobium-silicon alloy substrate, showing good compatibility.

[0050] The XRD patterns of the high-temperature anti-oxidation coatings on the niobium-silicon alloy surfaces prepared in Examples 1-4 are shown below. Figure 2 As shown. By Figure 2 It can be seen that the elements in the high-temperature anti-oxidation coating on the surface of the niobium-silicon alloy prepared by the present invention mainly exist in the form of Al(Nb,Ti), Ti5Si4, Nb3Si2, Nb3Si and Ti5Si3.

[0051] The high-temperature anti-oxidation coating on the niobium-silicon alloy surface prepared in Example 1 was placed in a high-temperature box furnace for oxidation resistance testing. The furnace was held at 1300°C in air for 800 hours, then removed and cooled to room temperature with air. The microstructure of the oxidized coating was characterized using scanning electron microscopy, and the results are as follows: Figure 3 As shown, the scanning electron microscope (SEM) image of the coating cross-section and the elemental distribution map are as follows: Figure 4 As shown. By Figure 3It can be seen that after oxidation at 1300℃ for 800 hours, a dense Al2O3 oxide layer can be formed on the surface of the anti-oxidation coating, and the protective film does not peel off, providing excellent high-temperature oxidation resistance to the niobium-silicon alloy substrate. Figure 4 It can be seen that after the anti-oxidation coating is oxidized at 1300℃ for 800h, the element distribution inside the coating changes significantly, with Al forming a dense Al2O3 oxide layer on the surface.

[0052] The niobium-silicon alloy surface high-temperature anti-oxidation coatings prepared in Examples 2-4 were placed in a high-temperature box furnace for oxidation resistance testing. The furnace was held at 1300°C in air for 800 hours, then removed and cooled to room temperature with air. The microstructure of the oxidized coatings was characterized using scanning electron microscopy, and the results are as follows: Figures 5-7 As shown. By Figures 5-7 It can be seen that after oxidation at 1300℃ for 800 hours, a dense Al2O3 oxide layer can be formed on the surface of the anti-oxidation coating, and the protective film does not peel off, providing excellent high-temperature oxidation resistance for the niobium-silicon alloy substrate.

[0053] Comparative Example 1 Niobium-silicon alloy matrix (composition: Nb-26Ti-16Si-8Hf-3Al, surface without anti-oxidation coating) prepared by non-consumable vacuum arc melting.

[0054] The niobium-silicon alloy matrix provided in Comparative Example 1 was placed in a high-temperature box furnace for oxidation resistance testing. It was held at 1300℃ in air for 96 hours, then removed and cooled to room temperature with air. The microstructure of the oxidized niobium-silicon alloy matrix was characterized using scanning electron microscopy, and the results are as follows: Figure 8 As shown. By Figure 8 It can be seen that after oxidation at 1300℃ for 96 hours, the surface oxide layer is a composite oxide containing Nb, Si, Ti and Hf, with a large number of pores. There are also a large number of voids at the interface between the substrate and the oxide layer, indicating that the alloy substrate is severely oxidized. The oxide layer thickness exceeds 200μm, with high stress and poor adhesion, making it easy to peel off and with poor oxidation resistance.

[0055] Comparative Example 2 A niobium-silicon alloy surface coating, comprising the following components by atomic percentage: Nb: 13.5%; Ti: 23.5%; Si: 23.5%; Al: 36% and Hf: 3.5%; Other conditions are the same as in Example 1.

[0056] The niobium-silicon alloy surface coating provided in Comparative Example 2 was placed in a high-temperature box furnace for oxidation resistance testing. It was held at 1300℃ in air for 500 hours, then removed and cooled to room temperature with air. The microstructure of the oxidized niobium-silicon alloy surface coating was characterized using scanning electron microscopy, and the results are as follows: Figure 9 As shown. By Figure 9 It can be seen that after oxidation at 1300℃ for 500h, although a dense Al2O3 oxide layer was formed on the surface, the oxide layer had lost its bond with the coating in some areas, and the thickness of the oxide layer had reached 50μm.

[0057] The comparison between Examples 1-4 and Comparative Examples 1-2 shows that the high-temperature anti-oxidation coating on the surface of the niobium-silicon alloy provided by the present invention can provide excellent high-temperature oxidation resistance to the niobium-silicon alloy substrate.

[0058] 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. A high-temperature anti-oxidation coating for the surface of a niobium-silicon alloy, characterized in that, On an atomic percentage basis, it includes the following components: Nb: 12.5~13.4%; Ti: 20~25%; Si: 20~25%; Al: 34~38%; Hf: 3~6% and RE: 0.1~1%.

2. The high-temperature anti-oxidation coating on the surface of the niobium-silicon alloy according to claim 1, characterized in that, On an atomic percentage basis, it includes the following components: Nb: 12.5~13.4%; Ti: 23.5%; Si: 23.5%; Al：36%； Hf: 3.5% and RE: 0.1~1%.

3. The high-temperature anti-oxidation coating on the niobium-silicon alloy surface according to claim 1, characterized in that, On an atomic percentage basis, it includes the following components: Nb: 13%; Ti: 23.5%; Si: 23.5%; Al：36%； Hf: 3.5% and RE: 0.5%.

4. The high-temperature anti-oxidation coating on the surface of the niobium-silicon alloy according to any one of claims 1 to 3, characterized in that, The RE is either Y or Dy.

5. The method for preparing the high-temperature anti-oxidation coating on the surface of the niobium-silicon alloy according to any one of claims 1 to 4, characterized in that, Includes the following steps: (1) Alloy ingots are prepared by melting and smelting alloy raw materials; (2) The alloy ingot obtained in step (1) is crushed and ball-milled in sequence to obtain alloy powder; (3) Press the alloy powder obtained in step (2) to obtain a coating green blank, then combine the coating green blank with the niobium-silicon alloy substrate and sinter it, and finally perform homogenization heat treatment to obtain a high-temperature anti-oxidation coating on the surface of the niobium-silicon alloy.

6. The preparation method according to claim 5, characterized in that, In step (2), the ball-to-material ratio of ball milling is (40~60):1, and the total ball milling time is 24~48h. The ball milling method is to mill in both forward and reverse directions for 5~20min each, then stop cooling for 30~50min, and repeat the process.

7. The preparation method according to claim 5, characterized in that, The particle size of the alloy powder in step (2) is <20μm.

8. The preparation method according to claim 5, characterized in that, The pressure applied in step (2) is 10~20MPa, and the pressurization time is 1~3h.

9. The preparation method according to claim 5, characterized in that, In step (3), the sintering holding temperature is 1100~1200℃, the sintering holding time is 5~10min, and the sintering pressure is 25~35MPa.

10. The preparation method according to claim 5, characterized in that, In step (3), the holding temperature for homogenization heat treatment is 1200~1300℃, the holding time for homogenization heat treatment is 20~50h, and the vacuum degree for homogenization heat treatment is <10. -2 Pa.

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