Niobium alloy surface thermal spraying coating, preparation method and application

Abstract

The invention relates to the technical field of coating preparation, in particular to a niobium alloy surface thermal spraying coating, a preparation method and application, according to the method, a silicide coating is prepared on the niobium alloy surface, halide reaction embedding siliconizing treatment is conducted, and the niobium alloy surface thermal spraying coating is obtained; the silicide coating is prepared on the surface of the niobium alloy through the thermal spraying technology, the rough surface can be formed, anchoring sites are provided for follow-up halide reaction embedding siliconizing treatment, in the follow-up halide reaction embedding siliconizing treatment process, silicon is diffused to a base body to react to form a siliconizing diffusion layer, and metallurgical bonding of a coating-base body interface is achieved. In addition, a continuous transition area is formed between the siliconizing diffusion layer and the silicide coating, stress concentration caused by component mutation is reduced, the risk of interface cracking is effectively reduced, the service life of the coating is prolonged, and the problems that in the prior art, the interface bonding force between a thermal spraying MoSi2-based silicide coating and a base body is poor, and the service life is short are solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of coating preparation, in particular to a hot sprayed coating on the surface of a niobium alloy, a preparation method and application. BACKGROUND

[0002] Niobium alloy is widely used in aerospace thermal structure field due to its high melting point (>2400℃), excellent high-temperature mechanical properties and low density. However, the insufficient oxidation resistance of niobium alloy is a key problem in the process of thermal service application, especially under the condition of higher than 600℃, the alloy surface is easy to form a brittle and low melting point Nb2O5 oxide layer, which leads to rapid failure of the material. To solve this problem, silicide coating, especially MoSi2-based coating, is considered as the most potential thermal protection scheme due to its excellent high-temperature oxidation resistance, matching thermal expansion coefficient with niobium alloy and the ability to form a self-healing SiO2 protective film at high temperature.

[0003] In recent years, hot sprayed MoSi2-based silicide coating has been widely used in the oxidation resistance of niobium alloy due to its high deposition efficiency, strong designability, small thermal damage to the substrate and easy industrial production. The Chinese invention patent with the authorization publication number CN107190261B discloses a high-temperature oxidation-resistant composite silicide coating on the surface of niobium alloy and a preparation method, which uses halide vapor pack infiltration method to prepare NbSi2 inner coating containing Al2O3 adsorption particles; uses atmospheric inner powder supersonic plasma spraying method to prepare MoSi2 outer coating. The Chinese invention patent with the authorization publication number CN115652302B discloses a high-temperature environmental barrier coating for niobium alloy and a preparation method, which uses halide reaction pack cementation to prepare a roughened Nb-Si coating, uses supersonic atmospheric plasma spraying process to prepare Mo-Si-Al-O oxidation-resistant coating and Yb-Si-Al-O environmental barrier coating. The above-mentioned patents both use halide activation pack cementation process and plasma spraying technology two-step method to prepare NbSi2-MoSi2 double-layer silicide oxidation-resistant coating on Nb521 type niobium alloy, and spray MoSi2 outer layer on the rough NbSi2 transition layer. Although the interface bonding of the sprayed coating is improved, the interface bonding strength is increased by 20% compared with that of single sprayed MoSi2 coating (14.6±2.1MPa), reaching 20.9±5.4MPa, and the coating system shows excellent oxidation resistance at 1500℃. However, the above-mentioned hot sprayed MoSi2-based silicide coating and niobium alloy substrate are mechanically bonded, which easily leads to coating / substrate interface debonding, coating cracking or peeling during high-low temperature thermal cycle service, seriously affecting its long-term service performance. SUMMARY

[0004] In view of the poor interface bonding force between the thermal spraying MoSi2-based silicide coating and the substrate and the short service life in the prior art, the application provides a niobium alloy surface thermal spraying coating, a preparation method and application.

[0005] To achieve the above object, the application adopts the following technical scheme: The application provides a preparation method of a niobium alloy surface thermal spraying coating, comprising: Preparation of a silicide coating on the surface of the niobium alloy to obtain a first combination; Halide reaction embedding silicon treatment of the first combination to obtain the niobium alloy surface thermal spraying coating.

[0006] Optionally, the method for preparing the silicide coating on the surface of the niobium alloy to obtain the first combination is: Preparation of a silicide spray drying slurry by using a silicide solid powder, a PVA aqueous solution, anhydrous ethanol and water; Atomization drying of the silicide spray drying slurry and sieving to obtain a thermal spraying solid powder; Deposition of the thermal spraying solid powder to the surface of the niobium alloy by using a plasma spraying process to obtain the first combination.

[0007] Optionally, the silicide solid powder is a MoSi2 and / or HfO2 modified MoSi2 solid powder, wherein the content of the modified component HfO2 in the HfO2 modified MoSi2 solid powder is less than or equal to 20wt.%.

[0008] Optionally, the mass ratio of the silicide solid powder, the PVA aqueous solution, the anhydrous ethanol and the water is 4:4:1:1.

[0009] Optionally, the particle size of the thermal spraying solid powder is 200-300 mesh.

[0010] Optionally, the method further comprises roughening treatment of the surface of the niobium alloy, which is: Roughening treatment of the surface of the niobium alloy by using a sand blasting machine, wherein the sand blasting pressure of the sand blasting machine is 0.5-0.6MPa, the sand blasting angle is 70-90° and the sand blasting distance is 80-100mm.

[0011] Optionally, the method for halide reaction embedding silicon treatment of the first combination to obtain the niobium alloy surface thermal spraying coating is: Embedding of the first combination in embedding powder and placing in an Ar atmosphere at 900-1100℃ for 2-3h for halide reaction embedding silicon treatment to obtain the niobium alloy surface thermal spraying coating.

[0012] Optionally, the embedding powder comprises 15wt.%-25wt.% of Si, 15wt.%-25wt.% of NH4F and 50-70wt.% of Al2O3.

[0013] A niobium alloy surface thermal spraying coating prepared by the preparation method of the niobium alloy surface thermal spraying coating, and the bonding strength between the niobium alloy surface thermal spraying coating and the surface of the niobium alloy is 39-43MPa.

[0014] The preparation method of the niobium alloy surface thermal spraying coating or the application of the niobium alloy surface thermal spraying coating in the preparation of aerospace devices.

[0015] Compared with the prior art, the present application has the following beneficial effects: The present application provides a preparation method of a niobium alloy surface thermal spraying coating, which comprises the following steps: preparing a silicide coating on the surface of the niobium alloy to obtain a first combination, and carrying out halide reaction embedding siliconizing treatment to obtain the niobium alloy surface thermal spraying coating; wherein the silicide coating is prepared on the surface of the niobium alloy by a thermal spraying process, which can form a rough surface to provide an anchoring site for the subsequent halide reaction embedding siliconizing treatment; during the subsequent halide reaction embedding siliconizing treatment, Si atoms react with the niobium matrix to form a siliconizing diffusion layer, thereby realizing the metallurgical bonding of the coating-substrate interface and improving the interface bonding strength. In addition, a continuous transition zone is formed between the siliconizing diffusion layer and the silicide coating, which reduces the stress concentration caused by the composition mutation and effectively reduces the risk of interface cracking. This technology provides a reliable interface bonding solution for the application of niobium alloys in high-temperature extreme environments, and is especially suitable for key fields such as aeroengines and spacecraft thermal protection.

[0016] The method for preparing the silicide coating on the surface of the niobium alloy to obtain the first combination comprises the following steps: preparing a silicide spray-dried slurry by using silicide solid powder, polyvinyl alcohol (PVA) aqueous solution, anhydrous ethanol and water; then, performing atomization drying on the silicide spray-dried slurry, and performing screening to obtain thermal spraying solid powder; and finally, depositing the thermal spraying solid powder onto the surface of the niobium alloy by using a plasma spraying process to obtain the first combination. The PVA aqueous solution acts as a binder to form a uniform and stable slurry together with the silicide solid powder, the anhydrous ethanol and the water. The spray-drying process causes the slurry to be rapidly atomized into tiny droplets, and the droplets are rapidly dried into solid particles under the action of hot air. This process can accurately control the particle size distribution and morphology of the particles, and the thermal spraying solid powder with high sphericity and uniform particle size is obtained. The spherical particles have good fluidity in the plasma spraying process, are easy to transport and accelerate, and are beneficial to the formation of a uniform and dense coating. The cooperation of the spray-drying granulation and the plasma spraying process can ensure that the powder is fully melted, and the bonding strength between the coating and the substrate is improved. The method is suitable for silicide powders with different compositions and particle sizes, and can prepare coatings meeting different working condition requirements by adjusting the slurry formula and the process parameters of the spray-drying and plasma spraying processes.

[0017] The silicide solid powder is MoSi2 and / or HfO2 modified MoSi2 solid powder. In the HfO2 modified MoSi2 solid powder, the content of the modified component HfO2 is less than or equal to 20wt.%. MoSi2 and HfO2 modified MoSi2 have high melting points and good high-temperature oxidation resistance, which can effectively improve the oxidation resistance, high-temperature stability and mechanical properties of the coating on the surface of the niobium alloy. The scheme has process adaptability and cost effectiveness.

[0018] The method for preparing the thermal spraying coating on the surface of the niobium alloy further comprises roughening treatment on the surface of the niobium alloy. The surface of the niobium alloy is roughened by using a sandblasting machine. The sandblasting pressure of the sandblasting machine is 0.5-0.6 MPa, the sandblasting angle is 70-90°, and the sandblasting distance is 80-100 mm. By the impact of high-pressure abrasive, micron-sized pits and protrusions can be formed on the surface of the niobium alloy, the surface roughness is significantly increased, more mechanical anchoring points are provided for the coating particles, and the mechanical bonding force between the coating and the substrate is enhanced. At the same time, after the roughening treatment, the actual contact area of the substrate surface is increased, the friction and van der Waals force between the coating and the substrate are enhanced, and the bonding strength is further improved.

[0019] The method for performing halide reaction embedding silicon treatment on the first combination to obtain the thermal spraying coating on the surface of the niobium alloy comprises the following steps: The first combination is buried in the embedding powder and placed in an Ar atmosphere at 900-1100 DEG C for 2-3 hours to perform halide reaction embedding silicon treatment, thereby obtaining a niobium alloy surface thermal spraying coating. The embedding powder comprises 15-25 wt.% of Si, 15-25 wt.% of NH4F and 50-70 wt.% of Al2O3. By performing halide reaction embedding silicon treatment in an Ar atmosphere at 900-1100 DEG C, silicon diffuses to the surface of the niobium alloy to form a siliconized diffusion layer, which can significantly improve the bonding strength of the coating and the substrate. Meanwhile, the silicide coating can form a stable SiO2 glass layer at high temperature, effectively blocking the diffusion of oxygen and significantly improving the oxidation resistance of the coating.

[0020] A niobium alloy surface thermal spraying coating prepared by the above-mentioned method for preparing a niobium alloy surface thermal spraying coating, wherein the bonding strength of the coating and the surface of the niobium alloy is 39-43 MPa. Due to the higher interfacial bonding strength of the coating and the surface of the niobium alloy, the coating has a longer service life in extreme environments, has low maintenance cost and can be used in key components such as turbine blades and combustion chambers, thereby improving the reliability and durability of the engine and reducing the maintenance cost.

[0021] The above-mentioned method for preparing a niobium alloy surface thermal spraying coating or the above-mentioned niobium alloy surface thermal spraying coating is applied in the preparation of aerospace devices. The application of the niobium alloy surface thermal spraying coating can meet the high requirements of the aerospace and energy fields for high-temperature component protection, has a wide application prospect and market value, the high bonding strength not only prolongs the service life of the component but also reduces the maintenance cost, and is an important breakthrough in high-temperature coating technology. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 It is a flow chart of the method for preparing a niobium alloy surface thermal spraying coating.

[0023] Figure 2 It is a tensile test result graph of the niobium alloy surface thermal spraying coating prepared in Example 1.

[0024] Figure 3 It is a tensile test result graph of the niobium alloy surface thermal spraying coating prepared in Example 2. DETAILED DESCRIPTION

[0025] In order for those skilled in the art to understand the characteristics and effects of the present application, the following is a general description and definition of the terms and phrases mentioned in the specification and claims. Unless otherwise specified, all technical and scientific words used in the text are the usual meanings understood by those skilled in the art of the present application, and in case of conflict, the definition in the specification shall prevail.

[0026] The theories or mechanisms described and disclosed herein, whether correct or incorrect, should not limit the scope of the present invention in any way, that is, the present invention can be implemented without being limited by any specific theory or mechanism.

[0027] All features, such as values, amounts, amounts, and concentrations, described herein as numerical ranges or percentage ranges are provided for simplicity and convenience only. Accordingly, the description of numerical ranges or percentage ranges should be considered to include and specifically disclose all possible subranges and individual values ​​within the range (including integers and fractions).

[0028] In this document, unless otherwise specified, “include,” “including,” “contains,” “has” or similar terms cover the meanings of “consisting of” and “mainly consisting of,” for example, “A includes a” covers the meanings of “A includes a and other” and “A only includes a.”

[0029] In this document, for the sake of brevity, not all possible combinations of the various technical features in each embodiment or example are described. Therefore, as long as there are no contradictions in the combination of these technical features, the various technical features in each embodiment or example can be combined in any way, and all possible combinations should be considered to be within the scope of this specification.

[0030] Below in conjunction with specific embodiment, further set forth the present invention.Should be understood that these embodiments are only used to illustrate the present invention and are not used in limiting the scope of the present invention.In addition, should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall equally within the scope limited by the appended claims of the application.

[0031] The following examples were prepared using conventional instruments and equipment in the art. Experimental methods in the following examples, where specific conditions are not specified, were generally performed under conventional conditions or according to the conditions recommended by the manufacturer. The various raw materials used in the following examples, unless otherwise specified, were conventional commercially available products, with specifications conventional in the art. In the present specification and the following examples, unless otherwise specified, "%" indicates percentage by weight, "part" indicates parts by weight, and "ratio" indicates weight ratio.

[0032] The present invention will be further described in detail below with reference to specific embodiments, which are intended to explain the present invention rather than to limit it.

[0033] See also Figure 1 A method for preparing a thermal spray coating on a niobium alloy surface comprises: S1: Preparing a silicide coating on the surface of the niobium alloy to obtain a first assembly, specifically: S1.1: Roughening treatment of niobium alloy surface: The surface of the niobium alloy is roughened by a sandblasting machine, the sandblasting pressure of the sandblasting machine is 0.5-0.6 MPa, the sandblasting angle is 70-90°, and the sandblasting distance is 80-100 mm.

[0034] S1.2: A silicide spray drying slurry is prepared by using a silicide solid powder, a PVA aqueous solution, anhydrous ethanol and water; the silicide solid powder is MoSi2 and / or HfO2 modified MoSi2 solid powder, wherein the content of the modified component HfO2 in the HfO2 modified MoSi2 solid powder is less than or equal to 20 wt.%; the mass ratio of the silicide solid powder, the PVA aqueous solution, the anhydrous ethanol and the water is 4:4:1:1; the concentration of the PVA aqueous solution is 2 wt.%; S1.3: The silicide spray drying slurry is atomized and dried, and sieved to obtain a thermal spraying solid powder: The atomization and drying are performed by using a spray dryer, the rotation speed of the spray drying nozzle is set to 30-40 r / min, the inlet temperature is 330-360℃, and the outlet temperature is 100-110℃; the dried powder is sieved by using a 200-300 mesh sieve to obtain the thermal spraying solid powder.

[0035] S1.4: The thermal spraying solid powder is deposited onto the roughened surface of the niobium alloy by using a plasma spraying process to obtain a first assembly: During spraying, the spraying power is 42-45 kW, the powder feeding rate is 1.4-1.6 r / min, the spraying pass is 6-7, and the spraying distance is 80-100 mm.

[0036] S2: The first assembly is subjected to halide reaction embedding silicon treatment to obtain a niobium alloy surface thermal spraying coating, specifically: The first assembly is placed in a graphite crucible and uniformly filled with a silicide solid powder, the crucible is wrapped with graphite paper and placed in an Ar atmosphere at 900-1100℃ for halide reaction embedding silicon treatment to achieve silicon enrichment, thereby obtaining a niobium alloy surface thermal spraying coating, wherein the embedding powder comprises 15-25 wt.% Si, 15-25 wt.% NH4F and 50-70 wt.% Al2O3.

[0037] Example 1 A Nb521 type niobium alloy sample in the form of a circular disc with a diameter of 20 mm and a thickness of 3 mm is obtained by using a wire cutting device, and a sandblasting device is used to roughen the surface of the pretreated sample, the sandblasting pressure is 0.6 MPa, the sandblasting angle is 90°, and the sandblasting distance is 100 mm; the sandblasted sample is again ultrasonically cleaned in anhydrous ethanol for 30 min and dried at 80℃; The MoSi2 solid powder, the PVA aqueous solution with a solid content of 2wt.%, anhydrous ethanol and deionized water are mixed in a mass ratio of 4:4:1:1 and put into a ball mill tank containing zirconia beads, and then ball milling is performed for 4h to obtain a silicide spray drying slurry; The silicide spray drying slurry is subjected to spray drying treatment, and the spray drying device nozzle rotation speed is set to 35r / min, and the feeding inlet temperature is 330℃; the dried powder is sieved using a 200 mesh screen to obtain a thermal spraying solid powder; The MoSi2 layer is deposited on the roughened Nb alloy surface by supersonic plasma spraying process to obtain a first combination; the spraying power is about 44kW, the powder feeding rate is 1.5r / min, the spraying pass is 6, and the spraying distance is 80mm; The first combination and the embedding powder are uniformly filled into a graphite crucible, and the embedding powder is composed of 20wt.% Si powder, 20wt.% NH4F and 60wt.% Al2O3 powder; the graphite crucible is placed in a high-temperature tube furnace, and the temperature is raised to 1100℃ at a rate of 5℃ / min under Ar atmosphere and kept for 2h, and then the temperature is lowered to 600℃ at a rate of 10℃ / min and naturally cooled to room temperature; the siliconized sample is taken out, ultrasonically cleaned in clean water for 30min, and dried at 80℃ to obtain a Nb alloy surface thermal spraying coating.

[0038] To test the bonding strength of the Nb alloy surface thermal spraying coating of the present application, a high-temperature adhesive is coated on both sides of a tensile mold, and the Nb alloy surface thermal spraying coating sample is placed in the mold, and then placed in a 100℃ oven for 4h to fully cure the high-temperature adhesive; After curing, the coating bonding strength is tested by using a CMT5304-30KN microcomputer control electronic universal testing machine, and the calculated bonding strength of the pure MoSi2 sprayed coating after silicon enrichment treatment with the Nb alloy substrate is 39MPa. See Figure 2 From the tensile force-displacement curve and the macroscopic morphology of the fracture interface, it can be seen that the pure MoSi2 sprayed coating after silicon enrichment treatment has strong interface bonding with the substrate, and there is siliconization phenomenon at the fracture.

[0039] Example 2 A Nb521 type Nb alloy sample in the form of a disc with a diameter of 20mm and a thickness of 3mm is obtained by using a wire cutting equipment, and the pretreated sample is subjected to sand blasting surface roughening by using a sand blasting equipment, the sand blasting pressure is 0.6MPa, the sand blasting angle is 90°, and the sand blasting distance is 100mm; the sand blasted sample is again ultrasonically cleaned in anhydrous ethanol for 30min and dried at 80℃; MoSi2 modified by HfO2, the content of modified component HfO2 is 20wt.% solid powder, the solid content of PVA aqueous solution is 2wt.%, the content of anhydrous ethanol is 4wt.%, and the content of deionized water is 1wt.%; the mixture is put into a ball mill tank containing zirconia balls, and ball milling is carried out for 4h to obtain a silicide spray drying slurry; The silicide spray drying slurry is subjected to spray drying treatment, and the rotation speed of the spray head of the spray drying equipment is set to 35r / min, and the inlet temperature of the feeding material is set to 330℃; the dried powder is sieved using a 200 mesh sieve to obtain a thermal spraying solid powder; A MoSi2-20wt.% HfO2 layer is deposited on the surface of the roughened niobium alloy by supersonic plasma spraying process to obtain a first combination; the spraying power is about 44kW, the powder feeding rate is 1.5r / min, the spraying pass is 6, and the spraying distance is 80mm; The first combination and the embedding powder are uniformly filled into a graphite crucible, and the embedding powder is composed of 20wt.% Si powder, 20wt.% NH4F and 60wt.% Al2O3 powder; the graphite crucible is placed in a high-temperature tubular heat treatment furnace, and heated to 1100℃ at a heating rate of 5℃ / min under Ar atmosphere and kept for 2h, and then cooled to 600℃ at a cooling rate of 10℃ / min and naturally cooled to room temperature; the siliconized sample is taken out, ultrasonically cleaned in clean water for 30min, and dried at 80℃ to obtain a niobium alloy surface thermal spraying coating.

[0040] In order to test the bonding strength of the niobium alloy surface thermal spraying coating of the present application, a high-temperature adhesive is coated on both sides of a tensile mold, and the niobium alloy surface thermal spraying coating sample is placed in the middle of the mold, and then placed in a 100℃ oven for 4h to fully cure the high-temperature adhesive; After curing, the experiment is carried out, and the tensile sample is subjected to coating bonding strength test by using a CMT5304-30KN microcomputer controlled electronic universal testing machine, and calculation shows that the bonding strength of the pure MoSi2 sprayed coating after silicon enrichment treatment with the Nb alloy substrate is 43MPa. See Figure 3 From the tensile force-displacement curve and the macroscopic morphology of the fracture interface, it can be seen that the interface bonding of the 20wt.% HfO2 modified MoSi2 based sprayed coating after silicon enrichment treatment is further enhanced, and there is obvious siliconization phenomenon in the fracture.

[0041] Comparative Example 1 Different from Example 2, the mass fraction of HfO2 in the silicide solid powder is 50wt.%. The presence of a large amount of HfO2 will change the thermal expansion coefficient of the MoSi2 based silicide coating, further induce thermal stress concentration and layer cracking, and is not conducive to improving the bonding strength of the sprayed coating.

[0042] Nb521 type niobium alloy samples in the form of a disc with a diameter of 20 mm and a thickness of 3 mm are obtained by using a wire cutting device, and the pretreated samples are subjected to sand blasting roughening of the surface by using a sand blasting device, the sand blasting pressure is 0.6 MPa, the sand blasting angle is 90°, and the sand blasting distance is 100 mm; the samples subjected to sand blasting treatment are again subjected to ultrasonic cleaning in anhydrous ethanol for 30 min, and are dried at 80℃; The MoSi2 is modified by HfO2, the content of the modified component HfO2 is 50wt.% solid powder, the solid content of the PVA aqueous solution is 2wt.%, and the contents of anhydrous ethanol and deionized water are 4:4:1:1 by mass ratio, which are mixed and placed in a ball mill tank containing zirconia balls, and then 4h ball milling is performed to obtain a silicide spray drying slurry; The silicide spray drying slurry is subjected to spray drying treatment, the spray drying device nozzle rotation speed is set to 35r / min, and the inlet temperature of the feeding material is set to 330℃; the dried powder is sieved using a 200 mesh sieve to obtain a thermal spraying solid powder; A MoSi2-50wt.% HfO2 layer is deposited on the roughened niobium alloy surface by using supersonic plasma spraying process to obtain a first combination; the spraying power is about 44kW, the powder feeding rate is 1.5r / min, the spraying pass is 6, and the spraying distance is 80mm; The first combination and the embedding powder are uniformly filled into a graphite crucible, the embedding powder is composed of 20wt.% Si powder, 20wt.% NH4F and 60wt.% Al2O3 powder; the graphite crucible is placed in a high-temperature tube furnace, and is heated to 1100℃ at a heating rate of 5℃ / min under Ar atmosphere and is kept for 2h, and then is cooled to 600℃ at a cooling rate of 10℃ / min and is naturally cooled to room temperature; the siliconized sample is taken out, is ultrasonically cleaned in clean water for 30min, and is dried at 80℃ to obtain a niobium alloy surface thermal spraying coating.

[0043] In order to test the bonding strength of the niobium alloy surface thermal spraying coating of the present application, a high-temperature adhesive is coated on both sides of a tensile mold, the niobium alloy surface thermal spraying coating sample is placed in the middle of the mold, and then is placed in a 100℃ oven for 4h to allow the high-temperature adhesive to fully cure; after curing, the experiment is carried out, the tensile sample is subjected to coating bonding strength test by using a CMT5304-30KN microcomputer controlled electronic universal testing machine, and the calculated bonding strength of the 50wt.% HfO2 modified MoSi2 based spraying coating after silicon enrichment treatment with the Nb alloy substrate is 19MPa.

[0044] Example 3 Nb521 type niobium alloy sample with a diameter of 20 mm and a thickness of 3 mm is obtained by using a wire cutting device, and the pretreated sample is subjected to sand blasting roughening surface by using a sand blasting device, the sand blasting pressure is 0.5 MPa, the sand blasting angle is 80°, and the sand blasting distance is 90 mm; the sample treated by sand blasting is ultrasonically cleaned in anhydrous ethanol for 30 min again, and dried at 80℃; The MoSi2 solid powder, the PVA aqueous solution with a solid content of 2wt.%, anhydrous ethanol and deionized water are mixed in a mass ratio of 4:4:1:1, and then put into a ball mill tank containing zirconia balls, and then ball milled for 4h to obtain a silicide spray drying slurry; The silicide spray drying slurry is subjected to spray drying treatment, and the spray drying device nozzle rotation speed is set to 30r / min, and the feeding inlet temperature is 360℃; the dried powder is sieved by using a 300 mesh sieve to obtain a thermal spraying solid powder; The MoSi2 layer is deposited on the roughened niobium alloy surface by using supersonic plasma spraying process to obtain a first combination; the spraying power is about 42kW, the powder feeding rate is 1.4r / min, the spraying pass is 7, and the spraying distance is 90mm; The first combination and the embedding powder are uniformly filled into a graphite crucible, and the embedding powder is composed of 15wt.% Si powder, 15wt.% NH4F and 70wt.% Al2O3 powder; the graphite crucible is placed in a high-temperature tube furnace, and heated to 1000℃ at a heating rate of 5℃ / min under Ar atmosphere and kept for 2h, and then cooled to 600℃ at a cooling rate of 10℃ / min and naturally cooled to room temperature; the siliconized sample is taken out, ultrasonically cleaned in clean water for 30min, and dried at 80℃ to obtain a niobium alloy surface thermal spraying coating.

[0045] In order to test the bonding strength of the niobium alloy surface thermal spraying coating of the present application, a high-temperature adhesive is coated on both sides of a tensile mold, and the niobium alloy surface thermal spraying coating sample is placed in the middle of the mold, and then placed in a 100℃ oven for 4 hours to fully cure the high-temperature adhesive; After curing, the experiment is carried out, and the tensile sample is tested for coating bonding strength by using a CMT5304-30KN microcomputer controlled electronic universal testing machine, and the calculated bonding strength of the pure MoSi2 sprayed coating after silicon enrichment treatment with the Nb alloy substrate is 40MPa.

[0046] Example 4 Nb521 type niobium alloy sample with a diameter of 20 mm and a thickness of 3 mm is obtained by using a wire cutting device, and the pretreated sample is subjected to sand blasting roughening surface by using a sand blasting device, the sand blasting pressure is 0.5 MPa, the sand blasting angle is 80°, and the sand blasting distance is 90 mm; the sample treated by sand blasting is ultrasonically cleaned in anhydrous ethanol for 30 min again, and dried at 80℃; MoSi2 solid powder, PVA aqueous solution with solid content of 2wt.%, anhydrous ethanol and deionized water were mixed in a mass ratio of 4:4:1:1 and put into a ball mill tank containing zirconia beads, and then ball milling was carried out for 4h to obtain a silicide spray drying slurry; The silicide spray drying slurry was subjected to spray drying treatment, and the spray drying device nozzle rotation speed was set to 35r / min, and the feeding inlet temperature was 330℃; the dried powder was sieved using a 200 mesh screen to obtain a thermal spraying solid powder; A MoSi2 layer was deposited on the roughened Nb alloy surface by supersonic plasma spraying process to obtain a first combination; the spraying power was about 44kW, the powder feeding rate was 1.5r / min, the spraying pass was 6, and the spraying distance was 80mm; The first combination and the embedding powder were uniformly filled into a graphite crucible, and the embedding powder was composed of 20wt.% Si powder, 20wt.% NH4F and 60wt.% Al2O3 powder; the graphite crucible was placed in a high-temperature tube furnace, and the temperature was raised to 1100℃ at a rate of 5℃ / min under Ar atmosphere and kept for 2h, and then the temperature was lowered to 600℃ at a rate of 10℃ / min and naturally cooled to room temperature; the siliconized sample was taken out, ultrasonically cleaned in clean water for 30min, and dried at 80℃ to obtain a Nb alloy surface thermal spraying coating.

[0047] To test the bonding strength of the Nb alloy surface thermal spraying coating of the present application, a high-temperature adhesive was coated on both sides of a tensile mold, and the Nb alloy surface thermal spraying coating sample was placed in the middle of the mold, and then placed in a 100℃ oven for 4h to fully cure the high-temperature adhesive; After curing, the experiment was carried out, and the tensile sample was tested for coating bonding strength by using a CMT5304-30KN microcomputer controlled electronic universal testing machine, and the calculated bonding strength of the pure MoSi2 sprayed coating after silicon enrichment treatment with the Nb alloy substrate was 42.3MPa.

[0048] Example 5 A Nb521 type Nb alloy sample in the form of a circular disc with a diameter of 20mm and a thickness of 3mm was obtained by using a wire cutting equipment, and the pretreated sample was subjected to sandblasting surface roughening by using a sandblasting equipment, the sandblasting pressure was 0.5MPa, the sandblasting angle was 80°, and the sandblasting distance was 90mm; the sandblasted sample was again ultrasonically cleaned in anhydrous ethanol for 30min and dried at 80℃; MoSi2 solid powder, PVA aqueous solution with solid content of 2wt.%, anhydrous ethanol and deionized water were mixed in a mass ratio of 4:4:1:1 and put into a ball mill tank containing zirconia beads, and then ball milling was carried out for 4h to obtain a silicide spray drying slurry; The silicide spray drying slurry is subjected to spray drying treatment, the rotation speed of the spray drying device nozzle is set to 40 r / min, and the feeding inlet temperature is 350℃; the dried powder is sieved using a 300 mesh screen to obtain the thermal spraying solid powder; A MoSi2 layer is deposited on the roughened niobium alloy surface by supersonic plasma spraying process to obtain a first assembly; the spraying power is about 43 kW, the powder feeding rate is 1.6 r / min, the spraying pass is 7, and the spraying distance is 100 mm. The first assembly and the embedding powder are uniformly filled into a graphite crucible, the embedding powder is composed of 25 wt.% Si powder, 20 wt.% NH4F and 55 wt.% Al2O3 powder; the graphite crucible is placed in a high-temperature tube furnace, heated to 1000℃ at a heating rate of 5℃ / min under Ar atmosphere and kept for 2 h, then cooled to 600℃ at a cooling rate of 10℃ / min and naturally cooled to room temperature; the siliconized sample is taken out, ultrasonically cleaned in clean water for 30 min, and dried at 80℃ to obtain the niobium alloy surface thermal spraying coating.

[0049] To test the bonding strength of the niobium alloy surface thermal spraying coating of the present application, a high-temperature adhesive is coated on both sides of a tensile mold, the niobium alloy surface thermal spraying coating sample is placed in the middle of the mold, and then placed in a 100℃ oven for 4 hours to allow the high-temperature adhesive to fully cure; After curing, the experiment is carried out, the tensile sample is tested for coating bonding strength by CMT5304-30KN microcomputer control electronic universal testing machine, and the calculated bonding strength of the pure MoSi2 sprayed coating after silicon enrichment treatment with the Nb alloy substrate is 39.5 MPa.

[0050] A niobium alloy surface thermal spraying coating prepared by the above-mentioned niobium alloy surface thermal spraying coating preparation method, the bonding strength of the niobium alloy surface thermal spraying coating with the niobium alloy surface is 39-43 MPa. Due to the higher interfacial bonding strength of the coating with the niobium alloy surface, the coating has a longer service life in extreme environments, low maintenance cost, and can be used for key components such as turbine blades and combustion chambers, improving the reliability and durability of the engine and reducing maintenance costs.

[0051] The above-mentioned niobium alloy surface thermal spraying coating preparation method or the above-mentioned application of the niobium alloy surface thermal spraying coating in the preparation of aerospace devices. The application of the niobium alloy surface thermal spraying coating can meet the high requirements of aerospace, energy and other fields for high-temperature component protection, has a broad application prospect and market value, and its high bonding strength not only prolongs the service life of the component, but also reduces the maintenance cost, which is an important breakthrough in high-temperature coating technology.

[0052] In summary, the present application proposes a niobium alloy surface thermal spraying coating, a preparation method and an application, taking niobium alloy as a substrate, preparing a silicide coating through a plasma spraying process, and further adopting a halide activation embedding method to perform silicon enrichment treatment on the sprayed coating, so as to improve the interface bonding strength of the thermal spraying silicide coating and the niobium alloy substrate. The method can provide an efficient and reliable solution for the engineering application of the niobium alloy ultrahigh-temperature oxidation-resistant coating, and has important application value in the field of aerospace hot end components.

[0053] The above merely describes the preferred embodiments of the present application and is not intended to limit the technical solutions of the present application in any way, and those skilled in the art should understand that the technical solutions can be simply modified and replaced without departing from the spirit and principles of the present application, and these modifications and replacements also belong to the protection scope covered by the claims.

Claims

1. A method for preparing a thermal spray coating on a niobium alloy surface, characterized in that: include: preparing a silicide coating on the surface of the niobium alloy to obtain a first assembly; The first assembly is subjected to a halide reaction embedding siliconization treatment to obtain a niobium alloy surface thermal spray coating.

2. The method for preparing a thermal spray coating on a niobium alloy surface according to claim 1, characterized in that: The method for preparing a silicide coating on the surface of the niobium alloy to obtain the first assembly is: Silicide spray drying slurry is prepared by using silicide solid powder, PVA aqueous solution, anhydrous ethanol and water; Atomizing and drying the silicide spray drying slurry, and sieving it to obtain a thermal spray solid powder; A plasma spraying process is used to deposit thermal spray solid powder onto the surface of the niobium alloy to obtain a first assembly.

3. The method for preparing a thermal spray coating on a niobium alloy surface according to claim 2, characterized in that: The silicide solid powder is MoSi2 and / or HfO2 modified MoSi2 solid powder, wherein: In the HfO2-modified MoSi2 solid powder, the content of the modified component HfO2 is less than or equal to 20 wt.%.

4. The method for preparing a thermal spray coating on a niobium alloy surface according to claim 2, characterized in that: The mass ratio of the silicate solid powder, PVA aqueous solution, anhydrous ethanol and water is 4:4:1:

1.

5. The method for preparing a thermal spray coating on a niobium alloy surface according to claim 1, characterized in that: The particle size of the thermal spraying solid powder is 200-300 meshes.

6. The method for preparing a thermal spray coating on a niobium alloy surface according to claim 1, characterized in that: The method also includes roughening the surface of the niobium alloy by: The surface of the niobium alloy is roughened by a sandblasting machine, the blasting pressure of the sandblasting machine is 0.5-0.6 MPa, the blasting angle is 70°-90°, and the blasting distance is 80-100 mm.

7. The method for preparing a thermal spray coating on a niobium alloy surface according to claim 1, characterized in that: The method of subjecting the first assembly to a halide reaction embedding siliconization treatment to obtain a thermal spray coating on the niobium alloy surface is: The first assembly is embedded in embedding powder and placed in an Ar atmosphere at 900° C. to 1100° C. for 2 to 3 hours to perform a halide reaction embedding siliconization treatment to obtain a thermal spray coating on the niobium alloy surface.

8. The method for preparing a thermal spray coating on a niobium alloy surface according to claim 7, characterized in that: The embedding powder comprises 15 wt.% to 25 wt.% of Si, 15 wt.% to 25 wt.% of NH4F and 50 to 70 wt.% of Al2O3.

9. A niobium alloy surface thermal spray coating prepared by the method for preparing a niobium alloy surface thermal spray coating according to any one of claims 1 to 8, characterized in that: The bonding strength between the thermal spray coating on the niobium alloy surface and the niobium alloy surface is 39-43 MPa.

10. The method for preparing the thermal spray coating on the surface of a niobium alloy according to any one of claims 1 to 8 or use of the thermal spray coating on the surface of a niobium alloy according to claim 9 in the preparation of aerospace components.

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