Superhigh-temperature coating for turbine blade and preparation method of superhigh-temperature coating

Abstract

The invention provides a superhigh-temperature coating for a steam turbine blade and a preparation method thereof, and relates to the technical field of material surface treatment. Comprising the following components in parts by mass: 20-30 parts of yttrium-stabilized zirconia, 15-20 parts of titanium aluminum nitride, 10-15 parts of lanthanum magnesium aluminate spinel, 5-10 parts of nano cerium oxide, 10-15 parts of cobalt-based alloy, 1-5 parts of a rare earth element mixture, 5-10 parts of hexagonal boron nitride, 5-10 parts of SiC nanoparticles and 2-5 parts of chromium carbide. Through the synergistic effect of the lanthanum magnesium aluminate spinel and the rare earth mixture, the grain growth rate of the coating is greatly reduced at a high temperature, so that the stability of the coating at an extreme temperature is improved, the chromium carbide is decomposed to form a protective layer, and the protective layer and the SiC nanoparticles jointly inhibit sulfur erosion, so that the stability is further improved, and the performance of the coating at the high temperature is ensured.

Description

Technical Field

[0001] The present invention relates to the technical field of material surface treatment, and in particular to an ultra-high temperature coating for a steam turbine blade and a preparation method thereof. Background Art

[0002] Steam turbine blades are the core components of the key power equipment, the steam turbine, with sophisticated design and vital functions. They are usually installed on the rim of the turbine rotor, rotating at a high circumferential speed, and are directly responsible for efficiently converting the thermal energy of the steam into mechanical energy. When the steam turbine is running, the high-temperature and high-pressure steam impacts the blades, driving them to rotate and drive the rotor, which in turn drives the generator to generate electricity or perform other mechanical work. Steam turbine blades not only withstand extremely high temperatures, pressures and centrifugal forces, but also face severe challenges such as impurities in the steam, corrosion, and wear and fatigue caused by long-term operation. Therefore, its material selection, structural design, manufacturing process and protective measures are extremely critical, and are directly related to the efficiency, reliability and service life of the steam turbine. Modern steam turbine blades are mostly made of advanced alloy materials, and use precise processing technology and surface coating treatment technology to ensure that they can still maintain excellent performance under extreme working conditions;

[0003] In the coating of turbine blades, traditional MCrAlY coatings are prone to forming loose Al2O3 films under high temperature conditions. Since the loose Al2O3 film cannot effectively protect the interior of the coating from oxidation, the coating material will gradually be oxidized, resulting in performance degradation and shortened service life. Traditional ceramic coatings, due to the difference in thermal expansion coefficient with the metal substrate, lead to interfacial stress concentration, which is prone to thermal shock peeling. In summary, traditional coatings have limited high-temperature stability. Therefore, the present invention proposes an ultra-high temperature coating for turbine blades and a preparation method thereof to solve the problems existing in the prior art. Summary of the Invention

[0004] In response to the above problems, the present invention proposes an ultra-high temperature coating for turbine blades and a preparation method thereof. The ultra-high temperature coating for turbine blades greatly reduces the grain growth rate of the coating at high temperatures through the synergistic effect of lanthanum magnesium aluminum spinel and a rare earth mixture, thereby improving the stability at extreme temperatures.

[0005] To achieve the purpose of the present invention, the present invention is implemented by the following technical solution: a super-high temperature coating for a steam turbine blade, comprising the following components by mass ratio: 20-30 parts of yttrium-stabilized zirconia (Y-ZrO2), 15-20 parts of titanium aluminum nitride (TiAlN), 15-20 parts of lanthanum magnesium aluminum spinel (LaMgAl 11 O 19) 10-15 parts, nano cerium oxide (CeO2) 5-10 parts, cobalt-based alloy (Co-Cr-Al-Y) 10-15 parts, rare earth element mixture 1-5 parts, hexagonal boron nitride (h-BN) 5-10 parts, SiC nanoparticles 5-10 parts, chromium carbide (Cr3C2) 2-5 parts.

[0006] The further improvement is that it includes the following mass ratio components: yttrium stabilized zirconia (Y-ZrO2) 25 parts, titanium aluminum nitride (TiAlN) 18 parts, lanthanum magnesium aluminum spinel (LaMgAl 11 O 19 ) 12 parts, nano cerium oxide (CeO2) 8 parts, cobalt-based alloy (Co-Cr-Al-Y) 12 parts, rare earth element mixture 3 parts, hexagonal boron nitride (h-BN) 8 parts, SiC nanoparticles 7 parts, chromium carbide (Cr3C2) 3 parts.

[0007] Further improvements are: the Y2O3 content in the yttrium-stabilized zirconia is 8%, and the particle size is 1-5 μm; the Al content in the titanium aluminum nitride is 60-70%, and the particle size is ≤10 μm.

[0008] Further improvements are: the atomic ratio of La:Mg:Al in the lanthanum magnesium aluminum spinel is 1:1:11; the particle size of the nano-cerium oxide is 5-10nm, and the purity is ≥99.9%; and the mass ratio of Co:Cr:Al:Y in the cobalt-based alloy is 70:20:8:2.

[0009] Further improvements are: in the rare earth element mixture, the mass ratio of La:Ce:Nb is 4:4:2; the purity of the hexagonal boron nitride is ≥98%, and the thickness of the layer is ≤1 μm.

[0010] A method for preparing an ultra-high temperature coating for a steam turbine blade comprises the following steps:

[0011] S1: The cobalt-based alloy is subjected to hydrogen reduction treatment, and titanium aluminum nitride and chromium carbide are ball-milled under argon;

[0012] S2: Add each component to anhydrous ethanol according to the ratio, ultrasonically disperse, then ball mill, and spray dry to obtain spherical composite powder;

[0013] S3: Using supersonic flame spraying method to spray the composite powder onto the turbine blade to form a coating;

[0014] S4: performing vacuum nitriding treatment and gradient annealing on the coating to solidify the coating.

[0015] Further improvement lies in that: in the S1, the cobalt-based alloy powder is subjected to hydrogen reduction treatment, the treatment is carried out at 600 DEG C for 2h, the flow rate of H2 is controlled to be 2L / min, the titanium aluminum nitride and the chromium carbide are subjected to ball milling treatment under argon, the ball milling is carried out for 4h, the ball-to-material ratio is controlled to be 8:1, and the rotating speed is 450 rpm.

[0016] Further improvement lies in that: in the S2, the components are added into anhydrous ethanol according to the proportion, the ultrasonic dispersion is carried out for 2h, then ball milling is carried out for 8h, spray drying is carried out to obtain spherical composite powder, the particle size distribution is controlled to be 20-80mu m, and the fluidity is controlled to be less than or equal to 25s / 50g.

[0017] Further improvement lies in that: in the S3, when the supersonic flame spraying method is adopted, the spraying fuel is C3H6 / O2 mixed gas, the flow rate ratio is 1:1.2, the fuel flow rate is controlled to be 250L / h, the spraying distance is 300mm, the sprayed substrate is preheated to 500 DEG C, and the thickness of the sprayed coating is controlled to be 150±15mu m.

[0018] Further improvement lies in that: in the S4, in the vacuum nitriding treatment, the temperature is controlled to be 1050 DEG C, the treatment is carried out for 3h, the nitrogen pressure is controlled to be 0.5MPa, and the gradient annealing includes the following stages: the treatment is carried out at 1200 DEG C for 1h under argon protection; the treatment is carried out at 800 DEG C for 4h under vacuum environment; and air cooling is carried out to room temperature.

[0019] The beneficial effects of the present application are:

[0020] 1. The present application realizes the synergistic effect of lanthanum magnesium aluminum spinel and rare earth mixture, greatly reduces the grain growth rate of the coating at high temperature, thereby improving the stability at extreme temperature, adopts chromium carbide to form a protective layer, and SiC nanoparticles are used to jointly inhibit sulfur corrosion, thereby further improving the stability and ensuring the performance of the coating under high temperature conditions.

[0021] 2. The cubic crystal structure of yttrium stabilized zirconium oxide and the face-centered cubic structure of titanium aluminum nitride form an atomic-level coherent interface, crack propagation is inhibited through the interface stress transmission mechanism, the coating fracture toughness is improved, the continuous gradient transition structure of lanthanum magnesium aluminum spinel and cobalt-based alloy effectively relieves the thermal stress concentration of the coating-substrate interface, the number of thermal shock cycles is improved, the layered crystal structure of hexagonal boron nitride provides self-lubricating function, and a lubricating film-reinforced phase composite system is formed with SiC nanoparticles, thereby reducing the wear rate and enhancing the erosion resistance. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 The flow chart of the present application. DETAILED DESCRIPTION

[0023] In order to deepen the understanding of the present application, the present application will be further described below in conjunction with examples, which are only used to explain the present application and do not constitute a limitation on the scope of protection of the present application.

[0024] Example 1

[0025] According to Figure 1 The present embodiment proposes a steam turbine blade ultra-high temperature coating, characterized by comprising the following mass ratio components: yttrium stabilized zirconia (Y-ZrO2) 20 parts, titanium aluminum nitride (TiAlN) 15 parts, lanthanum magnesium aluminum spinel (LaMgAl 11 O 19 ) 10 parts, nano cerium oxide (CeO2) 5 parts, cobalt-based alloy (Co-Cr-Al-Y) 10 parts, rare earth element mixture 1 part, hexagonal boron nitride (h-BN) 5 parts, SiC nanoparticles 5 parts, chromium carbide (Cr3C2) 2 parts.

[0026] Yttrium stabilized zirconia: through the doping of yttrium, the crystal form of zirconia is stabilized, and its thermal stability and oxidation resistance are improved. Titanium aluminum nitride: forms a hard phase, significantly improving the hardness and wear resistance of the coating. Lanthanum magnesium aluminum spinel: optimizes the microstructure of the coating, improves the thermal shock stability and oxidation resistance. Nano cerium oxide: as an oxidizing agent scavenger, effectively reduces oxidation damage. Cobalt-based alloy: provides high temperature strength and toughness, ensuring strong bonding of the coating and the substrate. Rare earth element mixture: optimizes coating performance, improves oxidation resistance and corrosion resistance. Hexagonal boron nitride: as a solid lubricant, reduces wear and extends the service life of the coating. SiC nanoparticles: enhance the hardness and wear resistance of the coating, improve the thermal stability. Chromium carbide: forms a hard phase, improves the hardness and oxidation resistance of the coating.

[0027] The Y2O3 content in the yttrium stabilized zirconia is 8%, and the particle size is 1-5 μm; the Al content in the titanium aluminum nitride is 60-70%, and the particle size is ≤10 μm. The atomic ratio of La:Mg:Al in the lanthanum magnesium aluminum spinel is 1:1:11; the particle size of the nano cerium oxide is 5-10 nm, and the purity is ≥99.9%; the mass ratio of Co:Cr:Al:Y in the cobalt-based alloy is 70:20:8:2. The mass ratio of La:Ce:Nb in the rare earth element mixture is 4:4:2; the purity of the hexagonal boron nitride is ≥98%, and the lamella thickness is ≤1 μm.

[0028] A preparation method of a steam turbine blade ultra-high temperature coating, comprising the following steps:

[0029] The cobalt-based alloy was subjected to hydrogen reduction treatment, and titanium aluminum nitride and chromium carbide were ball-milled under argon. The cobalt-based alloy powder was subjected to hydrogen reduction treatment at 600°C for 2 hours, with the flow rate of H2 controlled at 2 L / min, and titanium aluminum nitride and chromium carbide were ball-milled under argon for 4 hours, with a ball-to-material ratio of 8:1 and a rotation speed of 450 rpm.

[0030] The components were added to anhydrous ethanol according to the ratio, ultrasonically dispersed, ball milled, and spray-dried to obtain spherical composite powders; the components were added to anhydrous ethanol according to the ratio, ultrasonically dispersed for 2 hours, ball milled for 8 hours, and spray-dried to obtain spherical composite powders with a controlled particle size distribution of 20-80 μm and a flowability of ≤25 s / 50 g;

[0031] The composite powder was sprayed onto the turbine blades using a supersonic flame spraying method to form a coating. When using the supersonic flame spraying method, the spraying fuel was a C3H6 / O2 mixed gas with a flow ratio of 1:1.2. The fuel flow rate was controlled at 250 L / h, the spraying distance was 300 mm, the sprayed substrate was preheated to 500°C, and the coating thickness after spraying was controlled to 150±15 μm.

[0032] The coating was cured by vacuum nitriding and gradient annealing. The vacuum nitriding treatment was conducted at a controlled temperature of 1050°C for 3 hours and a nitrogen pressure of 0.5 MPa. The gradient annealing phase consisted of the following stages: 1 hour at 1200°C under argon protection; 4 hours at 800°C under vacuum; and air cooling to room temperature. Nitriding combined with gradient annealing resulted in a continuous Cr2N-TiN layer on the surface, improving wear resistance by threefold (friction coefficient 0.15 → 0.05). Directed h-BN distribution was achieved by controlling the spray angle to achieve parallel arrangement of the h-BN flakes, increasing thermal conductivity to 28 W / (m·K). Under 1400°C gas spray conditions (flow rate 120 m / s), the coating life was ≥5000 hours, and thermal cycling stress was reduced by 72%.

[0033] Example 2

[0034] according to Figure 1 As shown, this embodiment proposes an ultra-high temperature coating for turbine blades, comprising the following components by mass ratio: 25 parts of yttrium-stabilized zirconia (Y-ZrO2), 18 parts of titanium aluminum nitride (TiAlN), and 18 parts of lanthanum magnesium aluminum spinel (LaMgAl 11 O 19 ) 12 parts, nano cerium oxide (CeO2) 8 parts, cobalt-based alloy (Co-Cr-Al-Y) 12 parts, rare earth element mixture 3 parts, hexagonal boron nitride (h-BN) 8 parts, SiC nanoparticles 7 parts, chromium carbide (Cr3C2) 3 parts.

[0035] Yttrium-stabilized zirconia: By doping with yttrium, the crystal form of zirconia is stabilized, and its thermal stability and oxidation resistance are improved. Titanium aluminum nitride: forms a hard phase, significantly improving the hardness and wear resistance of the coating. Lanthanum magnesium aluminum spinel: optimizes the microstructure of the coating, improves thermal shock stability and oxidation resistance. Nano-cerium oxide: acts as an oxidant scavenger, effectively reducing oxidation damage. Cobalt-based alloy: provides high-temperature strength and toughness, ensuring strong bonding between the coating and the substrate. Rare earth element mixture: optimizes coating performance, improves oxidation resistance and corrosion resistance. Hexagonal boron nitride: acts as a solid lubricant, reduces wear, and extends the service life of the coating. SiC nanoparticles: enhance the hardness and wear resistance of the coating, and improve thermal stability. Chromium carbide: forms a hard phase, improving the hardness and oxidation resistance of the coating.

[0036] The yttrium-stabilized zirconia has an 8% Y2O3 content and a particle size of 1-5 μm; the titanium aluminum nitride has an Al content of 60-70% and a particle size of ≤10 μm. The lanthanum magnesium aluminum spinel has an atomic ratio of La:Mg:Al of 1:1:11; the nano-cerium oxide has a particle size of 5-10 nm and a purity of ≥99.9%; the cobalt-based alloy has a Co:Cr:Al:Y mass ratio of 70:20:8:2; the rare earth element mixture has a La:Ce:Nb mass ratio of 4:4:2; and the hexagonal boron nitride has a purity of ≥98% and a flake thickness of ≤1 μm.

[0037] A method for preparing an ultra-high temperature coating for a steam turbine blade comprises the following steps:

[0038] The cobalt-based alloy was subjected to hydrogen reduction treatment, and titanium aluminum nitride and chromium carbide were ball-milled under argon. The cobalt-based alloy powder was subjected to hydrogen reduction treatment at 600°C for 2 hours, with the flow rate of H2 controlled at 2 L / min, and titanium aluminum nitride and chromium carbide were ball-milled under argon for 4 hours, with a ball-to-material ratio of 8:1 and a rotation speed of 450 rpm.

[0039] The components were added to anhydrous ethanol according to the ratio, ultrasonically dispersed, ball milled, and spray-dried to obtain spherical composite powders; the components were added to anhydrous ethanol according to the ratio, ultrasonically dispersed for 2 hours, ball milled for 8 hours, and spray-dried to obtain spherical composite powders with a controlled particle size distribution of 20-80 μm and a flowability of ≤25 s / 50 g;

[0040] The composite powder was sprayed onto the turbine blades using a supersonic flame spraying method to form a coating. When using the supersonic flame spraying method, the spraying fuel was a C3H6 / O2 mixed gas with a flow ratio of 1:1.2. The fuel flow rate was controlled at 250 L / h, the spraying distance was 300 mm, the sprayed substrate was preheated to 500°C, and the coating thickness after spraying was controlled to 150±15 μm.

[0041] The coating is vacuum nitrided and gradient annealed to solidify the coating. In the vacuum nitriding process, the temperature is controlled at 1050°C for 3h, the nitrogen pressure is controlled at 0.5MPa, and the gradient annealing includes the following stages: 1200°C for 1h under argon protection, 800°C for 4h under vacuum, and air cooling to room temperature. Nitriding + gradient annealing: a continuous Cr2N-TiN layer is formed on the surface, the wear resistance is improved by 3 times (friction coefficient 0.15→0.05); h-BN directional distribution: h-BN lamellae are arranged in parallel by controlling the spraying angle, and the thermal conductivity is improved to 28W / (m·K). Under the condition of 1400°C gas scouring (flow rate 120m / s), the coating life is ≥5000h; the thermal cycle stress is reduced by 72%.

[0042] Example Three

[0043] According to Figure 1 The embodiment proposes a super-high-temperature coating for steam turbine blades, including the following components by mass: yttrium-stabilized zirconia (Y-ZrO2) 30 parts, titanium aluminum nitride (TiAlN) 20 parts, lanthanum magnesium aluminum spinel (LaMgAl 11 O 19 ) 15 parts, nano cerium oxide (CeO2) 10 parts, cobalt-based alloy (Co-Cr-Al-Y) 15 parts, rare earth element mixture 5 parts, hexagonal boron nitride (h-BN) 10 parts, SiC nanoparticles 10 parts, and chromium carbide (Cr3C2) 5 parts.

[0044] Yttrium-stabilized zirconia: through yttrium doping, the crystal form of zirconia is stabilized, improving its thermal stability and oxidation resistance. Titanium aluminum nitride: forms a hard phase, significantly improving the hardness and wear resistance of the coating. Lanthanum magnesium aluminum spinel: optimizes the microstructure of the coating, improves the thermal shock stability and oxidation resistance. Nano cerium oxide: as an oxidizing agent scavenger, effectively reduces oxidation damage. Cobalt-based alloy: provides high-temperature strength and toughness, ensuring strong bonding of the coating to the substrate. Rare earth element mixture: optimizes coating performance, improves oxidation resistance and corrosion resistance. Hexagonal boron nitride: as a solid lubricant, reduces wear and extends the service life of the coating. SiC nanoparticles: enhance the hardness and wear resistance of the coating, improve the thermal stability. Chromium carbide: forms a hard phase, improving the hardness and oxidation resistance of the coating.

[0045] The yttrium-stabilized zirconia has an 8% Y2O3 content and a particle size of 1-5 μm; the titanium aluminum nitride has an Al content of 60-70% and a particle size of ≤10 μm. The lanthanum magnesium aluminum spinel has an atomic ratio of La:Mg:Al of 1:1:11; the nano-cerium oxide has a particle size of 5-10 nm and a purity of ≥99.9%; the cobalt-based alloy has a Co:Cr:Al:Y mass ratio of 70:20:8:2; the rare earth element mixture has a La:Ce:Nb mass ratio of 4:4:2; and the hexagonal boron nitride has a purity of ≥98% and a flake thickness of ≤1 μm.

[0046] A method for preparing an ultra-high temperature coating for a steam turbine blade comprises the following steps:

[0047] The cobalt-based alloy was subjected to hydrogen reduction treatment, and titanium aluminum nitride and chromium carbide were ball-milled under argon. The cobalt-based alloy powder was subjected to hydrogen reduction treatment at 600°C for 2 hours, with the flow rate of H2 controlled at 2 L / min, and titanium aluminum nitride and chromium carbide were ball-milled under argon for 4 hours, with a ball-to-material ratio of 8:1 and a rotation speed of 450 rpm.

[0048] The components were added to anhydrous ethanol according to the ratio, ultrasonically dispersed, ball milled, and spray-dried to obtain spherical composite powders; the components were added to anhydrous ethanol according to the ratio, ultrasonically dispersed for 2 hours, ball milled for 8 hours, and spray-dried to obtain spherical composite powders with a controlled particle size distribution of 20-80 μm and a flowability of ≤25 s / 50 g;

[0049] The composite powder was sprayed onto the turbine blades using a supersonic flame spraying method to form a coating. When using the supersonic flame spraying method, the spraying fuel was a C3H6 / O2 mixed gas with a flow ratio of 1:1.2. The fuel flow rate was controlled at 250 L / h, the spraying distance was 300 mm, the sprayed substrate was preheated to 500°C, and the coating thickness after spraying was controlled to 150±15 μm.

[0050] The coating was cured by vacuum nitriding and gradient annealing. The vacuum nitriding treatment was conducted at a controlled temperature of 1050°C for 3 hours and a nitrogen pressure of 0.5 MPa. The gradient annealing phase consisted of the following stages: 1 hour at 1200°C under argon protection; 4 hours at 800°C under vacuum; and air cooling to room temperature. Nitriding combined with gradient annealing resulted in a continuous Cr2N-TiN layer on the surface, improving wear resistance by threefold (friction coefficient 0.15 → 0.05). Directed h-BN distribution was achieved by controlling the spray angle to achieve parallel arrangement of the h-BN flakes, increasing thermal conductivity to 28 W / (m·K). Under 1400°C gas spray conditions (flow rate 120 m / s), the coating life was ≥5000 hours, and thermal cycling stress was reduced by 72%.

[0051] According to the first, second and third embodiments, it can be concluded that the present invention adopts the following mass ratio components: yttrium stabilized zirconia (Y-ZrO2) 20-30 parts, titanium aluminum nitride (TiAlN) 15-20 parts, lanthanum magnesium aluminum spinel (LaMgAl 11 O 19 ) 10-15 parts, nano cerium oxide (CeO2) 5-10 parts, cobalt-based alloy (Co-Cr-Al-Y) 10-15 parts, rare earth element mixture 1-5 parts, hexagonal boron nitride (h-BN) 5-10 parts, SiC nanoparticles 5-10 parts, chromium carbide (Cr3C2) 2-5 parts, the prepared coating has stronger stability under extreme temperatures.

[0052] Verification example:

[0053]

[0054] The present invention utilizes the synergistic effect of lanthanum magnesium aluminum spinel and a rare earth mixture to reduce the coating's grain growth rate by 80% at high temperatures, thereby improving stability at extreme temperatures. The decomposition of chromium carbide to form a protective layer, which, together with SiC nanoparticles, inhibits sulfur corrosion, further improving stability and ensuring the coating's performance under high-temperature conditions. Furthermore, the cubic crystal structure of the yttrium-stabilized zirconia and the face-centered cubic structure of titanium aluminum nitride form an atomically coherent interface, inhibiting crack propagation through an interfacial stress transfer mechanism and improving the coating's fracture toughness. The lanthanum magnesium aluminum spinel and the cobalt-based alloy form a continuous gradient transition structure, effectively alleviating thermal stress concentration at the coating-substrate interface and increasing the number of thermal shock cycles. The layered crystal structure of hexagonal boron nitride provides self-lubrication and, together with the SiC nanoparticles, forms a lubricating film-reinforcement phase composite system, reducing wear rate while enhancing erosion resistance.

[0055] The basic principles, main features, and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the foregoing embodiments. The foregoing embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and modifications are intended to fall within the scope of the present invention. The scope of protection claimed in the present invention is defined by the appended claims and their equivalents.

Claims

1. An ultra-high temperature coating for a steam turbine blade, characterized in that: The composition includes the following mass ratio: yttrium stabilized zirconia (Y-ZrO2) 20-30 parts, titanium aluminum nitride (TiAlN) 15-20 parts, lanthanum magnesium aluminum spinel (LaMgAl 11 O 19 ) 10-15 parts, nano cerium oxide (CeO2) 5-10 parts, cobalt-based alloy (Co-Cr-Al-Y) 10-15 parts, rare earth element mixture 1-5 parts, hexagonal boron nitride (h-BN) 5-10 parts, SiC nanoparticles 5-10 parts, chromium carbide (Cr3C2) 2-5 parts.

2. The ultra-high temperature coating for steam turbine blades according to claim 1, characterized in that: The material includes the following components by weight: 25 parts of yttrium stabilized zirconia (Y-ZrO2), 18 parts of titanium aluminum nitride (TiAlN), 18 parts of lanthanum magnesium aluminum spinel (LaMgAl 11 O 19 ) 12 parts, nano cerium oxide (CeO2) 8 parts, cobalt-based alloy (Co-Cr-Al-Y) 12 parts, rare earth element mixture 3 parts, hexagonal boron nitride (h-BN) 8 parts, SiC nanoparticles 7 parts, chromium carbide (Cr3C2) 3 parts.

3. The ultra-high temperature coating for steam turbine blades according to claim 1, characterized in that: The Y2O3 content in the yttrium-stabilized zirconia is 8%, and the particle size is 1-5 μm; the Al content in the titanium aluminum nitride is 60-70%, and the particle size is ≤10 μm.

4. The ultra-high temperature coating for steam turbine blades according to claim 1, characterized in that: The atomic ratio of La:Mg:Al in the lanthanum magnesium aluminum spinel is 1:1:11; the particle size of the nano-cerium oxide is 5-10nm, and the purity is ≥99.9%; and the mass ratio of Co:Cr:Al:Y in the cobalt-based alloy is 70:20:8:

2.

5. The ultra-high temperature coating for steam turbine blades according to claim 1, characterized in that: In the rare earth element mixture, the mass ratio of La:Ce:Nb is 4:4:2; the purity of the hexagonal boron nitride is ≥98%, and the thickness of the sheet is ≤1 μm.

6. A method for preparing an ultra-high temperature coating for a steam turbine blade, applied to the ultra-high temperature coating for a steam turbine blade according to any one of claims 1 to 5, characterized in that: The following steps are involved: S1: The cobalt-based alloy is subjected to hydrogen reduction treatment, and titanium aluminum nitride and chromium carbide are ball-milled under argon; S2: Add all components into anhydrous ethanol according to the ratio, ultrasonically disperse, then ball mill, and spray dry to obtain spherical composite powder; S3: Using supersonic flame spraying method to spray the composite powder onto the turbine blade to form a coating; S4: performing vacuum nitriding treatment and gradient annealing on the coating to solidify the coating.

7. The method for preparing an ultra-high temperature coating for a steam turbine blade according to claim 6, characterized in that: In S1, the cobalt-based alloy powder is subjected to hydrogen reduction treatment at 600° C. for 2 h, with the H2 flow rate controlled at 2 L / min, and titanium aluminum nitride and chromium carbide are ball-milled under argon for 4 h, with the ball-to-material ratio controlled at 8:1 and the rotation speed at 450 rpm.

8. The method for preparing an ultra-high temperature coating for a steam turbine blade according to claim 6, wherein: In S2, each component is added to anhydrous ethanol according to the ratio, ultrasonically dispersed for 2 hours, ball milled for 8 hours, and spray-dried to obtain a spherical composite powder with a controlled particle size distribution of 20-80 μm and a fluidity of ≤25 s / 50 g.

9. The method for preparing an ultra-high temperature coating for a steam turbine blade according to claim 6, characterized in that: In S3, when the supersonic flame spraying method is used, the spraying fuel is a C3H6 / O2 mixed gas with a flow ratio of 1:1.2, the fuel flow is controlled at 250L / h, the spraying distance is 300mm, the sprayed substrate is preheated to 500°C, and the coating thickness after spraying is controlled to 150±15μm.

10. The method for preparing an ultra-high temperature coating for a steam turbine blade according to claim 6, characterized in that: In the S4, during the vacuum nitriding treatment, the temperature is controlled at 1050° C. for 3 hours, the nitrogen pressure is controlled at 0.5 MPa, and the gradient annealing includes the following stages: treatment at 1200° C. for 1 hour with argon protection; treatment at 800° C. for 4 hours in a vacuum environment; and air cooling to room temperature.

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