A high temperature environment barrier coating for niobium alloy and preparation method thereof

Abstract

The present invention relates to a high-temperature environmental barrier coating for niobium alloy and a preparation method thereof. The coating system sequentially comprises a Nb-Si bonding layer, a Mo-Si-Al-O anti-oxidation layer and a Yb-Si-Al-O environmental barrier outer layer on the surface of the niobium alloy. The coating preparation comprises: preparing a surface roughened Nb-Si coating by halide reaction embedding infiltration, and preparing a Mo-Si-Al-O anti-oxidation coating and a Yb-Si-Al-O environmental barrier coating by supersonic atmospheric plasma spraying. Yb 2 SiO 5 、MoSi 2 As well as the good thermophysical compatibility of niobium alloys, Yb 2 SiO 5 High toughness of doped components and Yb 2 SiO 5 Excellent water vapor corrosion resistance gives the coating better bonding strength and adaptability to high-temperature water vapor environments, improves the damage tolerance of the coating, and enhances the high-temperature water-oxygen corrosion protection effect of niobium alloy at 1500°C.

Description

Technical Field

[0001] The invention belongs to the technical field of coatings and relates to a high-temperature environment barrier coating for niobium alloys and a preparation method thereof. Background Art

[0002] Niobium alloy is considered to be the first choice material for the blades of the new generation of aircraft engines, replacing nickel-based single crystal alloys. Although a variety of high-efficiency silicide coatings have been developed to address the high-temperature oxidation problem of niobium alloys, the protective effect of the coating system with silicide as the working layer is poor in the face of oxygen, water vapor and other corrosive media in the harsh engine environment. Therefore, in order to ensure the long-term stable service of niobium alloys, it is necessary to apply an environmental barrier coating on its surface to isolate it from the harsh environment of the engine and to match its thermomechanical properties.

[0003] MoSi2 is widely used in protective coatings for niobium alloys in high-temperature oxygen-containing environments because of its similar thermal expansion coefficient to that of Nb alloys and the ability to generate a dense and protective SiO2 oxygen barrier film at high temperatures. However, in environments above 1200°C, the production of crystalline SiO2 will increase the number of defects such as cracks in the oxide film and reduce the protective ability of the silicide coating. Studies have shown that by adding a certain amount of mullite to the silicide coating, the above process can be effectively inhibited and the service life of the coating can be extended (G. Zhang, J. Sun, Q. Fu, Effect of mullite on the microstructure and oxidation behavior of thermal-sprayed MoSi2 coating at 1500°C [J], Ceramics International, 2020, 46 (6): 10058-10066.). In addition, due to the presence of high-temperature water vapor in the engine environment, the generated oxygen barrier layer SiO2 will be consumed to generate gaseous Si(OH)4 and lose its protective effect (E.Sooby Wood, SS Parker, AT Nelson, SA Maloy, MoSi2 Oxidation in 670-1498K Water Vapor, Journal of the American Ceramic Society, 2016, 99(4): 1412-1419.). Therefore, in order to achieve stable service of niobium alloy in such multiple oxidation (oxygen, water vapor) environments, it is necessary to deposit an environmental barrier coating material with low SiO2 activity on the surface of the oxygen barrier silicide coating to improve the high-temperature environment adaptability of the coating system.

[0004] Ytterbium silicate (Yb2SiO5, Yb2Si2O7) is widely used as environmental barrier coating materials due to its good comprehensive performance (D.Tejero-Martin, C.Bennett, T.Hussain, A review on environmental barrier coatings: History, current state of the art and future developments, Journal of the European Ceramic Society, 2021, 41(3): 1747-1768.). Among them, Yb2SiO5 has excellent water-oxygen corrosion resistance (Z.Tian, ​​J.Zhang, L.Sun, L.Zheng, J.Wang, Robust hydrophobicity and evaporation inertness of rare-earth monosilicates in hot steam at very high temperature, Journal of the American Ceramic Society, 2019, 102(6): 3076-3080.) and a thermal expansion coefficient similar to that of MoSi2 and Nb alloys (Yb2SiO5: 7~8×10 -6 K -1 ; MoSi2: 8~9×10 -6 K -1 ; Nb alloy: 7.6~8.5K -1 ), can be used as an environmental barrier coating material on the surface of Nb alloys. Compared with Yb2SiO5, although the difference in thermal expansion coefficient between Yb2Si2O7 and niobium alloys is larger, it has higher toughness (X.Wang, Z.Xue, Z.Zhou, E.Byon, S.Zhang, Influence of Yb2Si2O7 doping concentration on mechanical propertiesand thermal conductivity of Yb2SiO5-Yb2Si2O7 composite ceramics, Journal ofAlloys and Compounds, 2022, 889:161718.).

[0005] There are few studies on water-oxygen corrosion protection of Nb alloys in the prior art. Studies have shown that Y2SiO5 can be used for short-term protection of Nb alloys in a 1300°C, high-speed steam (about 5m / s) environment (after 1h of corrosion, the coating will decompose and peel off quickly) (A. Lange, R. Braun, P. Mechnich, CCBüttner, U. Schulz, L. Portebois, S. Mathieu, M. Vilasi, S. Drawin, Y2SiO5 environmental barrier coatings for niobium silicidebased materials, Materials at High Temperatures, 2015, 32 (1-2): 74-80.). High air inlet temperature plays an important role in ensuring the high efficiency of the engine, so it is necessary to explore the water-oxygen corrosion protection of Nb alloys at higher temperatures.

[0006] In summary, Yb2SiO5 can be used as an ideal high-temperature environmental barrier coating material on the surface of Nb alloy due to its excellent high-temperature water-oxygen corrosion resistance and good thermophysical compatibility with Nb alloy. However, the low fracture toughness of Yb2SiO5 and the poor water-oxygen corrosion resistance of the spray decomposition product Yb2O3 will limit its thermal cycling service life at higher temperatures. Therefore, improving the toughness of Yb2SiO5 environmental barrier coating and reducing the content of spray decomposition product Yb2O3 are of great significance for improving the high-temperature environment adaptability of Nb alloy surface coating system. Summary of the invention

[0007] Technical issues to be solved

[0008] In order to avoid the shortcomings of the prior art, the present invention proposes a high-temperature environmental barrier coating for niobium alloy and a preparation method thereof, which ensures the water-oxygen corrosion protection of Nb alloy at higher temperatures and makes up for the shortcomings of pure Yb2SiO5 as a raw material for plasma spray environmental barrier coating (low toughness of pure Yb2SiO5 and poor water-oxygen corrosion resistance of decomposition product Yb2O3). The Nb-Si bonding layer, Mo-Si-Al-O anti-oxidation layer and Yb-Si-Al-O outer layer are prepared on the surface of niobium alloy by halide reaction embedding and plasma spraying processes in sequence. The environmental barrier coating constructed by the present invention has a thermal expansion coefficient matching that of the substrate, and at the same time, Yb2Si2O7 and Mullite (in-situ reaction to generate Yb3Al5O 12 ) improves the toughness of the coating and enhances the high-temperature water-oxygen corrosion protection effect of the niobium alloy at 1500°C.

[0009] Technical Solution

[0010] A high-temperature environmental barrier coating for niobium alloy, characterized in that it comprises a bonding layer, an anti-oxidation layer and an environmental barrier outer layer, wherein the surface of the niobium alloy is a Nb-Si bonding layer, the middle is a Mo-Si-Al-O anti-oxidation layer, and the outer layer is a Yb-Si-Al-O environmental barrier outer layer; the Mo-Si-Al-O anti-oxidation layer adopts MoSi2-5wt.% Mullite solid powder; the Yb-Si-Al-O environmental barrier outer layer adopts Yb2SiO5-10wt.% Yb2Si2O7-10wt.% Mullite, Yb2SiO5 or Yb2SiO5-10wt.% Yb2Si2O7 solid powder.

[0011] A method for preparing a high temperature environment barrier coating for niobium alloys, characterized by the following steps:

[0012] Step 1: placing the sandblasted niobium alloy in a crucible, and evenly filling the embedding powder into the crucible, placing the crucible in a high-temperature tubular heat treatment furnace, and performing halide reaction embedding siliconization treatment at 1000-1100° C. in an Ar atmosphere to prepare a Nb-Si bonding layer;

[0013] The embedding powder is: 10-20wt.% Si powder, 10-20wt.% NH4F and 60-80wt.% Al2O3 powder; made by ball milling;

[0014] Step 2: MoSi2-5wt.% Mullite solid powder, PVA aqueous solution with a solid content of 2wt.%, anhydrous ethanol and deionized water are mixed and ball-milled into a slurry at a solid-liquid mass ratio of 4:4:1:1 to obtain a Mo-Si-Al-O anti-oxidation layer spray drying slurry;

[0015] Then, the slurry is physically and chemically dried at a temperature of 320 to 350° C., and the dried powder is sieved using a screen to obtain a solid powder of a Mo-Si-Al-O anti-oxidation layer spray drying slurry for spraying;

[0016] Step 3: using a plasma spraying process to deposit a Mo-Si-Al-O anti-oxidation layer on the Nb-Si bonding layer on the surface of the niobium alloy that has been Si-infiltrated in step 1;

[0017] Step 4: Yb2SiO5-10wt.% Yb2Si2O7-10wt.% Mullite solid powder, PVA aqueous solution with a solid content of 2wt.%, anhydrous ethanol and deionized water are mixed and ball-milled at a solid-liquid mass ratio of 4:4:1:1 to obtain a Yb-Si-Al-O environmental barrier outer layer spray-dried slurry;

[0018] Then, the slurry is physically and chemically dried at a temperature of 320-350° C., and the dried powder is sieved using a screen to obtain a solid powder after spray-drying the Yb-Si-Al-O environmental barrier outer layer slurry for spraying;

[0019] Step 5: Depositing a Yb-Si-Al-O environmental barrier outer layer on the surface of the niobium alloy on which the Mo-Si-Al-O anti-oxidation layer is deposited by a plasma spraying process.

[0020] The Yb2SiO5-10wt.% Yb2Si2O7-10wt.% Mullite solid powder in step 4 is replaced by Yb2SiO5 or Yb2SiO5-10wt.% Yb2Si2O7 solid powder.

[0021] The sandblasting roughening treatment of the niobium alloy is as follows: the sandblasting pressure is 0.5-0.6 MPa, the sandblasting angle is 70-90°, and the sandblasting distance is 80-100 mm.

[0022] The ball milling time for preparing the embedding powder in step 1 is 1 to 3 hours.

[0023] The ball milling time for preparing the slurry in step 2 is 3 to 5 hours.

[0024] The ball milling time for preparing the slurry in step 2 and step 4 is 3 to 5 hours.

[0025] The physical and chemical drying in step 2 and step 4 is performed using a spray dryer, and the rotation speed of the spray dryer nozzle is set to 30-40 rpm.

[0026] The spraying power in step 3 is 40-45 kW, and the spraying distance is 80-100 mm.

[0027] The spraying power in step 5 is 40-50 kW, and the spraying distance is 80-100 mm.

[0028] Beneficial Effects

[0029] The present invention proposes a high-temperature environmental barrier coating for niobium alloy and a preparation method thereof, wherein the coating system sequentially comprises a Nb-Si bonding layer, a Mo-Si-Al-O anti-oxidation layer and a Yb-Si-Al-O environmental barrier outer layer on the surface of the niobium alloy. The coating preparation comprises: preparing a surface-roughened Nb-Si coating by halide reaction embedding infiltration, and preparing a Mo-Si-Al-O anti-oxidation coating and a Yb-Si-Al-O environmental barrier coating by supersonic atmospheric plasma spraying. The good thermophysical compatibility of Yb2SiO5, MoSi2 and niobium alloy, the high toughness of the Yb2SiO5 doped component and the excellent water vapor corrosion resistance of Yb2SiO5 give the coating better bonding strength and adaptability to high-temperature water vapor environment, improve the damage tolerance of the coating, and enhance the high-temperature water oxygen corrosion protection effect of the niobium alloy at 1500°C.

[0030] The three-layer coating of the present invention has a thermal expansion coefficient that matches that of the substrate, and the coating interface is well bonded (the bonding strength of the plasma sprayed Yb2SiO5 / MoSi2-Mullite interface reaches 22MPa). By adding Yb2Si2O7 and Mullite to the Yb2SiO5 outer layer, the content of Yb2O3, a decomposition product of Yb2SiO5 spraying, in the outer layer can be effectively reduced, and the porosity of the outer layer is reduced. The coating samples all show a weight gain state during the 1500°C water-oxygen environment test. In addition, when Yb2Si2O7 and Mullite are co-doped, the formation of a low-melting-point eutectic product of Yb2Si2O7 and Mullite during the spraying process reduces the microcracks introduced in the sprayed coating due to the difference in the thermal expansion coefficients of Yb2Si2O7 and Yb2SiO5. At the same time, during the oxidation process, due to the in-situ dispersion generation of Yb3Al5O 12 , enhancing the toughness of the outer layer and effectively inhibiting the initiation and expansion of microcracks. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 The tensile test data of Yb2SiO5 / MoSi2-Mullite prepared by plasma spraying in Example 1 of the present invention are as follows:

[0032] (a) Tensile force-displacement curve;

[0033] (b) Interface bonding strength and macroscopic morphology of fracture interface. It can be seen that the sample is completely fractured along the Yb2SiO5 / MoSi2-Mullite interface after tensile testing, and the calculated interface bonding strength is 22MPa.

[0034] Figure 2 The cross-sectional microstructure of the sample prepared in the embodiment of the present invention is as follows:

[0035] (a) Sample with Yb2SiO5 as the outer layer;

[0036] (b) Sample with outer layer of Yb2SiO5-Yb2Si2O7;

[0037] (c) Sample with the outer layer being Yb2SiO5-Yb2Si2O7-Mullite.

[0038] Figure 3 The mass change and outer layer porosity of the sample in the embodiment of the present invention after being oxidized at 1500°C in a 50vol.% O2+50vol.% H2O environment for 20h:

[0039] (a) Mass change; (b) outer layer porosity.

[0040] Figure 4 The phase composition and microstructure of the sample in Example 3 of the present invention after being oxidized at 1500°C in a 50 vol.% O2+50 vol.% H2O environment for 20 hours:

[0041] (a) Cross-sectional backscattering morphology and corresponding element line scan data;

[0042] (b) Enlarged morphology of the outer layer and near the outer layer;

[0043] (c) The enlarged morphology and corresponding phase composition of the corresponding part of (b). Yb3Al5O with high fracture toughness is generated in situ in the outer layer. 12 , enhancing the cyclic service stability of the coating. DETAILED DESCRIPTION

[0044] The present invention will now be further described with reference to the embodiments and the accompanying drawings:

[0045] Embodiment 1:

[0046] Step 1: Use wire cutting equipment to obtain a size of 10×10×3mm 3 The niobium alloy samples were polished by a grinder to remove the surface oxide scale and sharp edges, and then ultrasonically cleaned in anhydrous ethanol for 20 minutes and dried at 80°C. The pre-treated samples were sandblasted to roughen the surface with a sandblasting pressure of 0.6MPa, a sandblasting angle of 90°, and a sandblasting distance of 100mm. The sandblasted samples were ultrasonically cleaned in anhydrous ethanol for 30 minutes and dried at 80°C.

[0047] Step 2: uniformly fill the sandblasted sample and the embedding powder obtained in step 1 into a graphite crucible, wherein the embedding powder consists of 20wt.% Si powder, 20wt.% NH4F and 60wt.% Al2O3 powder; place the graphite crucible in a high-temperature tubular heat treatment furnace, heat the temperature to 1100°C at a heating rate of 5°C / min under an Ar atmosphere and keep it warm for 2h, then cool the temperature to 400°C at a cooling rate of 10°C / min and naturally cool to room temperature; take out the siliconized sample, ultrasonically clean it in anhydrous ethanol for 30min, and dry it at 80°C;

[0048] Step 3: Mix MoSi2-5wt.% Mullite solid powder, PVA aqueous solution with a solid content of 2wt.%, anhydrous ethanol and deionized water in a mass ratio of 4:4:1:1 and put them into a ball mill filled with zirconia balls, and ball mill them for 4 hours to obtain a bonding layer 2 slurry; mix Yb2SiO5 solid powder, PVA aqueous solution with a solid content of 2wt.%, anhydrous ethanol and deionized water in a mass ratio of 4:4:1:1 and put them into a ball mill filled with zirconia balls, and ball mill them for 4 hours to obtain an outer layer slurry;

[0049] Step 4: spray-dry the bonding layer 2 and the outer layer slurry obtained in step 3, set the nozzle speed of the spray drying equipment to 35 rpm, and the feed inlet temperature to 330°C; use a 200-mesh screen to sieve the dried powder to obtain MoSi2-5wt.% Mullite and Yb2SiO5 solid powders for spraying;

[0050] Step 5: Deposit a MoSi2-5wt.% Mullite bonding layer 2 on the surface of the Si-infiltrated sample obtained in step 2 by supersonic plasma spraying, with a spraying power of 40kW and a spraying distance of 100mm; Continue to deposit a Yb2SiO5 outer layer on the surface of the MoSi2-5wt.% Mullite bonding layer 2 by plasma spraying, with a spraying power of 50kW and a spraying distance of 100mm ( Figure 2 (as shown in (a)).

[0051] Step 6: The above sample was oxidized at 1500℃, 50vol.%O2+50vol.%H2O environment for 20h and showed a weightless state, with a mass change of -2.28mg / cm 2 ( Figure 3 (as shown in (a)).

[0052] Embodiment 2:

[0053] Step 1: Use wire cutting equipment to obtain a size of 10×10×3mm 3The niobium alloy samples were polished by a grinder to remove the surface oxide scale and sharp edges, and then ultrasonically cleaned in anhydrous ethanol for 20 minutes and dried at 80°C. The pre-treated samples were sandblasted to roughen the surface with a sandblasting pressure of 0.6MPa, a sandblasting angle of 90°, and a sandblasting distance of 100mm. The sandblasted samples were ultrasonically cleaned in anhydrous ethanol for 30 minutes and dried at 80°C.

[0054] Step 2: uniformly fill the sandblasted sample and the embedding powder obtained in step 1 into a graphite crucible, wherein the embedding powder consists of 20wt.% Si powder, 20wt.% NH4F and 60wt.% Al2O3 powder; place the graphite crucible in a high-temperature tubular heat treatment furnace, heat the temperature to 1100°C at a heating rate of 5°C / min under an Ar atmosphere and keep it warm for 2h, then cool the temperature to 400°C at a cooling rate of 10°C / min and naturally cool to room temperature; take out the siliconized sample, ultrasonically clean it in anhydrous ethanol for 30min, and dry it at 80°C;

[0055] Step 3: Mix MoSi2-5wt.% Mullite solid powder, PVA aqueous solution with a solid content of 2wt.%, anhydrous ethanol and deionized water in a mass ratio of 4:4:1:1 and put them into a ball mill filled with zirconia balls, and ball mill them for 4 hours to obtain a bonding layer 2 slurry; mix Yb2SiO5-10wt.% Yb2Si2O7 solid powder, PVA aqueous solution with a solid content of 2wt.%, anhydrous ethanol and deionized water in a mass ratio of 4:4:1:1 and put them into a ball mill filled with zirconia balls, and ball mill them for 4 hours to obtain an outer layer slurry;

[0056] Step 4: spray-dry the bonding layer 2 and the outer layer slurry obtained in step 3, set the nozzle speed of the spray drying equipment to 35 rpm, and the feed inlet temperature to 330°C; use a 200-mesh sieve to sieve the dried powder to obtain MoSi2-5wt.%Mullite and Yb2SiO5-10wt.%Yb2Si2O7 solid powders for spraying;

[0057] Step 5: Deposit a MoSi2-5wt.% Mullite bonding layer 2 on the surface of the Si-infiltrated sample obtained in step 2 by supersonic plasma spraying, with a spraying power of 40kW and a spraying distance of 100mm; Continue to deposit a Yb2SiO5-10wt.% Yb2Si2O7 outer layer on the surface of the MoSi2-5wt.% Mullite bonding layer 2 by plasma spraying, with a spraying power of 45kW and a spraying distance of 100mm ( Figure 2 (as shown in (b)).

[0058] Step 6: The above sample was oxidized at 1500℃, 50vol.%O2+50vol.%H2O for 20h and showed a weight gain state, with a mass change of 1.35mg / cm 2 ( Figure 3 (as shown in (a)).

[0059] Embodiment three:

[0060] Step 1: Use wire cutting equipment to obtain a size of 10×10×3mm 3 The niobium alloy samples were polished by a grinder to remove the surface oxide scale and sharp edges, and then ultrasonically cleaned in anhydrous ethanol for 20 minutes and dried at 80°C. The pre-treated samples were sandblasted to roughen the surface with a sandblasting pressure of 0.6MPa, a sandblasting angle of 90°, and a sandblasting distance of 100mm. The sandblasted samples were ultrasonically cleaned in anhydrous ethanol for 30 minutes and dried at 80°C.

[0061] Step 2: uniformly fill the sandblasted sample and the embedding powder obtained in step 1 into a graphite crucible, wherein the embedding powder consists of 20wt.% Si powder, 20wt.% NH4F and 60wt.% Al2O3 powder; place the graphite crucible in a high-temperature tubular heat treatment furnace, heat the temperature to 1100°C at a heating rate of 5°C / min under an Ar atmosphere and keep it warm for 2h, then cool the temperature to 400°C at a cooling rate of 10°C / min and naturally cool to room temperature; take out the siliconized sample, ultrasonically clean it in anhydrous ethanol for 30min, and dry it at 80°C;

[0062] Step 3: Mix MoSi2-5wt.% Mullite solid powder, PVA aqueous solution with a solid content of 2wt.%, anhydrous ethanol and deionized water in a mass ratio of 4:4:1:1 and put them into a ball mill filled with zirconium oxide balls, and ball mill them for 4 hours to obtain a bonding layer 2 slurry; Mix Yb2SiO5-10wt.% Yb2Si2O7-10wt.% Mullite solid powder, PVA aqueous solution with a solid content of 2wt.%, anhydrous ethanol and deionized water in a mass ratio of 4:4:1:1 and put them into a ball mill filled with zirconium oxide balls, and ball mill them for 4 hours to obtain an outer layer slurry;

[0063] Step 4: spray-dry the bonding layer 2 and the outer layer slurry obtained in step 3, set the nozzle speed of the spray drying equipment to 35 rpm, and the feed material inlet temperature to 330°C; use a 200-mesh sieve to sieve the dried powder to obtain MoSi2-5wt.% Mullite and Yb2SiO5-10wt.% Yb2Si2O7-10wt.% Mullite solid powders for spraying;

[0064] Step 5: Deposit a MoSi2-5wt.% Mullite bonding layer 2 on the surface of the Si-infiltrated sample obtained in step 2 by supersonic plasma spraying, with a spraying power of 40kW and a spraying distance of 100mm; Continue to deposit a Yb2SiO5-10wt.% Yb2Si2O7-10wt.% Mullite outer layer on the surface of the MoSi2-5wt.% Mullite bonding layer 2 by plasma spraying, with a spraying power of 45kW and a spraying distance of 100mm ( Figure 2 (c)).

[0065] Step 6: The above sample was oxidized at 1500℃, 50vol.%O2+50vol.%H2O environment for 20h and showed a weight gain state, with a mass change of 0.05mg / cm 2 ( Figure 3 (a) Figure 4 shown).

[0066] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Improvements and modifications without departing from the principle of the present invention should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing a high temperature environment barrier coating for niobium alloy, characterized in that Here are the steps: Step 1: placing the sandblasted niobium alloy in a crucible, and evenly filling the embedding powder into the crucible, placing the crucible in a high-temperature tubular heat treatment furnace, and performing halide reaction embedding siliconization treatment at 1000-1100° C. in an Ar atmosphere to prepare a Nb-Si bonding layer; The embedding powder is: 10-20wt.% Si powder, 10-20wt.% NH4F and 60-80wt.% Al2O3 powder; made by ball milling; Step 2: MoSi2-5wt.% Mullite solid powder, PVA aqueous solution with a solid content of 2wt.%, anhydrous ethanol and deionized water are mixed and ball-milled into a slurry at a solid-liquid mass ratio of 4:4:1:1 to obtain a Mo-Si-Al-O anti-oxidation layer spray drying slurry; Then, the slurry is physically and chemically dried at a temperature of 320 to 350° C., and the dried powder is sieved using a screen to obtain a solid powder of a Mo-Si-Al-O anti-oxidation layer spray drying slurry for spraying; Step 3: using a plasma spraying process to deposit a Mo-Si-Al-O anti-oxidation layer on the Nb-Si bonding layer on the surface of the niobium alloy that has been Si-infiltrated in step 1; Step 4: Yb2SiO5-10wt.% Yb2Si2O7-10wt.% Mullite solid powder, PVA aqueous solution with a solid content of 2wt.%, anhydrous ethanol and deionized water are mixed and ball-milled at a solid-liquid mass ratio of 4:4:1:1 to obtain a Yb-Si-Al-O environmental barrier outer layer spray-dried slurry; Then, the slurry is physically and chemically dried at a temperature of 320-350° C., and the dried powder is sieved using a screen to obtain a solid powder after spray-drying the Yb-Si-Al-O environmental barrier outer layer slurry for spraying; Step 5: Depositing a Yb-Si-Al-O environmental barrier outer layer on the surface of the niobium alloy on which the Mo-Si-Al-O anti-oxidation layer is deposited by a plasma spraying process.

2. The method according to claim 1, characterized in that: The Yb2SiO5-10wt.% Yb2Si2O7-10wt.% Mullite solid powder in step 4 is replaced by Yb2SiO5 or Yb2SiO5-10wt.% Yb2Si2O7 solid powder.

3. The method according to claim 1, characterized in that: The sandblasting roughening treatment of the niobium alloy is as follows: the sandblasting pressure is 0.5-0.6 MPa, the sandblasting angle is 70-90°, and the sandblasting distance is 80-100 mm.

4. The method according to claim 1, characterized in that: The ball milling time for preparing the embedding powder in step 1 is 1 to 3 hours.

5. The method according to claim 1, characterized in that: The ball milling time for preparing the slurry in step 2 is 3 to 5 hours.

6. The method according to claim 1, characterized in that: The ball milling time for preparing the slurry in step 2 and step 4 is 3 to 5 hours.

7. The method according to claim 1, characterized in that: The physical and chemical drying in step 2 and step 4 is performed using a spray dryer, and the rotation speed of the spray dryer nozzle is set to 30-40 rpm.

8. The method according to claim 1, characterized in that: The spraying power in step 3 is 40-45 kW, and the spraying distance is 80-100 mm.

9. The method according to claim 1, characterized in that: The spraying power in step 5 is 40-50 kW, and the spraying distance is 80-100 mm.

10. A high temperature environment barrier coating for niobium alloy prepared by the method according to any one of claims 1 to 9, characterized in that It comprises a bonding layer, an anti-oxidation layer and an environmental barrier outer layer, wherein the surface of the niobium alloy is a Nb-Si bonding layer, the middle is a Mo-Si-Al-O anti-oxidation layer, and the outer layer is a Yb-Si-Al-O environmental barrier outer layer; the Mo-Si-Al-O anti-oxidation layer adopts MoSi2-5wt.%Mullite solid powder; the Yb-Si-Al-O environmental barrier outer layer adopts Yb2SiO5-10wt.%Yb2Si2O7-10wt.%Mullite, Yb2SiO5 or Yb2SiO5-10wt.%Yb2Si2O7 solid powder.

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