Preparation method of high-toughness low-conductivity anti-radiation thermal barrier coating

Abstract

The invention discloses a preparation method of a high-toughness low-conductivity anti-radiation thermal barrier coating. The invention belongs to the technical field of thermal barrier coating materials. Aiming at the problems of thermal expansion mismatch of a precious metal second phase, failure of a multilayer structure interface and insufficient toughness of a glass ceramic-based coating in an existing coating, the invention provides a composite gradient structure design. By introducing the glass ceramic intermediate layer and the gradient functional surface layer and combining plasma spraying and high-temperature sintering processes, the characteristics of high toughness, low heat conductivity, radiation resistance and high-temperature self-healing of the coating are realized. The method comprises the following specific steps: step 1, substrate pretreatment; step 2, bonding layer preparation; step 3, glass ceramic intermediate layer deposition; step 4, functional surface layer gradient spraying; the thermal conductivity of the obtained coating is lower than 0.8 W / (m.K), the bonding strength is larger than 35 MPa, the fracture toughness reaches 4.0 MPa.m < 1 / 2 >, the infrared reflectivity at the waveband of 0.3-10 microns is larger than 0.85, and microcrack self-healing can be achieved at the temperature of 1200 DEG C. The method is suitable for ultra-high-temperature service environments such as aero-engine turbine blades.

Description

Technical Field

[0001] The present invention belongs to the technical field of thermal barrier coating materials, and specifically relates to a method for preparing a high-toughness, low-conductivity radiation thermal barrier coating suitable for high-temperature protection applications such as aircraft engine turbine blades and gas turbine hot end components. Technical Background

[0002] As a core technology for improving turbine engine performance, thermal barrier coatings have become a key requirement in the fields of aviation, energy equipment, etc. by building a thermal insulation barrier on the surface of high-temperature components to reduce heat conduction. Although the current mainstream Y2O3 stabilized ZrO2 (YSZ) coating can provide a cooling effect of about 170K, its long-term operating temperature is limited to below 1200℃. The high-temperature phase change and thermal radiation penetration problems significantly restrict the development of a new generation of high thrust-to-weight ratio engines (thrust-to-weight ratio>10). As the gas temperature exceeds 1200℃, the radiation heat flux density can reach 2300000W·m -2 As mentioned above, the traditional low thermal conductivity coating has a sharp increase in thermal radiation penetration due to its infrared transmittance > 0.5, and the single-layer YSZ system can no longer meet the thermal shock protection requirements. Although new oxide materials such as niobate and hafnium oxide can reduce thermal conductivity (<1.5W·m -1 ·K-1) improves high-temperature stability, but the problem of thermal radiation penetration caused by its high infrared transmittance (>0.5) has become a common bottleneck. Existing solutions such as precious metal doping (platinum micro-sheets / nanoparticles) can reduce infrared transmittance through surface plasmon effects, but they face the high cost of precious metals (platinum prices exceed 3000 yuan / gram) and thermal expansion mismatch (metal-ceramic thermal expansion coefficient difference >8×10 -6 / K) and the high thermal conductivity introduced by the doping phase (the thermal conductivity of platinum is 71W·m -1 ·K-1) weakens the thermal insulation performance. Although the multi-layer structure design can improve the spectral reflectivity (such as 0.8 for the YSZ-Al2O3 system), the interface stress concentration leads to an increased risk of spalling. Experiments at Pennsylvania State University in the United States show that the probability of interface failure is as high as 37%. Although the gradient composite coating alleviates the thermal expansion mismatch, the increase in interfaces increases the complexity of the preparation process by more than 3 times, making it difficult to achieve engineering applications. In addition, although silicate glass ceramic materials have the characteristics of self-healing and low thermal conductivity (0.8W·m -1 ·K -1 ) and other advantages, but its intrinsic brittleness (fracture toughness <3MPa·m 1 / 2 ) results in a thermal shock life of less than 50 times, which cannot meet the ten thousand-hour service requirement of the gas turbine. In response to the above problems, it is urgent to develop a high toughness (>5MPa·m 1 / 2 ), low thermal conductivity (<1.2W·m -1 ·K -1), an integrated coating system that is resistant to radiation penetration (transmittance <0.3), and achieves interface optimization through innovative preparation processes. Current research shows that the use of plasma spray (PS) combined with EB-PVD technology can increase coating density to over 98%, while laser cladding technology can reduce thermal stress by 40% through gradient solidification control. This patent intends to break through existing technological bottlenecks by constructing a multi-scale composite structure combined with functional gradient design, providing a reliable thermal protection solution for ultra-high temperature turbine systems. Summary of the Invention

[0003] 1. The objects of the present invention are as follows:

[0004] The key problems of existing thermal barrier coatings are: 1. Interface cracking and spalling of precious metal second phase due to thermal expansion coefficient mismatch; 2. High failure probability of multi-layer structures due to interface stress concentration; 3. The intrinsic brittleness of glass-ceramic-based coatings makes it difficult to meet high-temperature and long-life service requirements.

[0005] By proposing a composite gradient structure design, combining material system optimization and process innovation, the aim is to prepare a material with high toughness and fracture toughness >4.0MPa·m 1 / 2 A thermal barrier coating with low thermal conductivity (<0.8W / (m·K)), radiation resistance, infrared reflectivity >0.85, and high-temperature self-healing properties. This coating can withstand ultra-high temperatures exceeding 1200°C, such as in aircraft engine turbine blades, significantly improving interfacial bonding strength and reducing thermal radiation transmittance. It also addresses the engineering challenges of traditional gradient coatings, which often face complex process steps and interface failure.

[0006] 2. The specific implementation process of the present invention is as follows:

[0007] A method for preparing a high-toughness and low-conductivity radiation thermal barrier coating, characterized in that the preparation method is completed according to the following steps:

[0008] Step 1. Substrate surface pretreatment: first remove the oxide film and grease on the substrate surface, then roughen the substrate surface, and finally perform thermal spray preheating on the substrate surface;

[0009] Step 2. Prepare the bonding layer: spray the bonding layer powder onto the workpiece surface using an atmospheric plasma spraying process to obtain a substrate with the bonding layer;

[0010] Step 3. Preparation of glass-ceramic intermediate layer: Modified silicate glass-ceramic powder is mixed with oxide dispersion and formed into an intermediate layer by plasma spraying with a thickness of 10-50 μm;

[0011] Step 4. Preparation of gradient functional surface layer:

[0012] Modified silicate glass ceramic powder;

[0013] Base phase component: low thermal conductivity ceramic, thermal conductivity <3W / (m·K);

[0014] Dispersed phase: functional ceramics, thermal conductivity <5W / (m·K), and microporous structure;

[0015] Mix the base phase, dispersed phase, and modified silicate glass ceramic powder in a gradient ratio, granulate them into spherical particles, and then spray them multiple times. Use plasma spraying to spray the spherical composite feed onto the surface of the substrate with the bonding layer. The volume fraction of the dispersed phase increases by 5-15% in each layer, and the final surface layer thickness is 50-500μm.

[0016] Step 5. High temperature sintering: Keep at 1000-1250°C for 0.5-2.0 hours to form a densified interface and a glass phase self-healing network.

[0017] In the above step 4, the base phase component is at least one of Y3NbO7, RE2Zr2O7 or modified YSZ, more preferably Y3NbO7;

[0018] The dispersed phase is at least one of GdTaO4, Al2O3 or doped rare earth zirconate, more preferably GdTaO4;

[0019] The substrate in step 1 is a metal-based material or a ceramic-based material, more preferably a metal-based material;

[0020] The metal-based material is a titanium-aluminum alloy, a nickel-based alloy or a niobium-based alloy, and is more preferably a nickel-based alloy;

[0021] The ceramic-based material is C / C, SiC / SiC, C / SiC or ZrB2-SiC;

[0022] In step 1, the method for removing the oxide film and grease on the surface of the substrate is to use sandpaper to polish the substrate to remove the oxide film, and then use one or more of solvent cleaning, steam cleaning, alkaline cleaning and heating degreasing methods to remove the substrate grease, and solvent cleaning is more preferably used;

[0023] In step 1, the method for roughening the substrate surface is sandblasting or laser texturing. When the substrate is a metal-based material, sandblasting is used, and when the substrate is a ceramic-based material, laser texturing is used. The parameters of the sandblasting are: sand particle size of 15-50, sandblasting pressure of 0.3-0.7 MPa; the parameters of the laser texturing are: laser power of 1-8 kW, pulse frequency of 10-20 Hz, spot size of 10-100 μm, and the roughness of the resulting texturized substrate surface is 1-5 μm.

[0024] The thermal spray preheating temperature in step 1 is 600-900°C, more preferably 800-900°C;

[0025] The bonding layer powder in step 2 needs to be selected according to the type of substrate. When the substrate is a metal-based material, the bonding layer powder is MCrAlY, where M is Ni, Co or NiCo, and more preferably NiCrAlY.

[0026] When the substrate is laser textured, the bonding layer powder is selected from RE-Si, wherein RE is a rare earth element, and the rare earth element is Hf or Y;

[0027] The atmospheric plasma spraying process described in step 2 is as follows: current 600A-650A, main airflow 40-50slpm, auxiliary airflow 3-10slpm, carrier airflow 1slpm-5slpm, powder feeding rate 1-3rpm;

[0028] The thickness of the bonding layer on the substrate with the bonding layer in step 2 is 20 μm-200 μm.

[0029] The present invention also discloses a method for preparing the modified silicate glass ceramic powder in step 3 as follows:

[0030] S1. Raw material pretreatment: Mixing silicate glass powder with Yb2O3 nanoparticles and Al2O3 chopped fibers in a mass ratio of (40-70): (5-15): (10-20);

[0031] S2. Sol-gel coating: The S1 mixed powder was dispersed in a tetraethyl orthosilicate solution, wherein the volume ratio of tetraethyl orthosilicate to ethanol and water was (1-3):(2-5):(1-2), and 0.1 mol / L HNO3 catalyst was added and ultrasonically stirred for 1-2 hours to form a sol; gelation was carried out in a 70-80°C water bath for 2-4 hours to obtain a nano-SiO2-coated composite gel powder;

[0032] S3 heat treatment: S2 the resulting composite gel powder was calcined at 400-600 ℃ for 2-3 hours to remove organic matter, and then annealed at 1000-1100 ℃ for 1-2 hours to form a nano-Yb2O3-Al2O3 fiber-reinforced glass ceramic powder;

[0033] Wherein, in the above S1 and S2, the quantitative ratio between the mass of the mixed powder (unit: g) and the volume of the ethyl orthosilicate solution (unit: ml) is 1:5;

[0034] The mass ratio of silicate glass powder, Yb2O3 nanoparticles and Al2O3 chopped fibers in S1 is (40-70):(5-15):(10-20), more preferably 60:10:15;

[0035] The volume ratio of ethyl orthosilicate to ethanol and water in S2 is (1-3):(2-5):(1-2), more preferably 2:3:1;

[0036] The softening temperature of the silicate glass ceramic in step 3 is ≥1000°C, the mass ratio of the silicate glass ceramic to the oxide dispersed phase YSZ or Al2O3 and the base phase ceramic is 7:3:3, and the porosity of the intermediate layer is 5-15%; the expansion coefficient of the base phase and the dispersed phase in step 4 is less than 1.2×10-6K -1 .

[0037] In the gradient functional surface layer of step 4, the micropore equivalent radius is 0.5-5 μm, the dispersed phase particle size is 0.3-10 μm, and the overall porosity of the surface layer is 8-20%.

[0038] The process of powder mixing and spherical granulation described in step 4 does not distinguish between the order of priority; when the powder mixing is performed first and then the spherical granulation is performed, the mixing process is as follows: a certain proportion of the base phase and the dispersed functional phase, the original powder of the modified silicate glass ceramic powder, anhydrous ethanol and zirconium oxide balls are placed in a planetary ball mill at a mass ratio of 1:0.1:3, and ball milled at a speed of 200r / min-400r / min for 6h-12h to obtain the original powder mixed slurry, and then the slurry is dried at 60℃-120℃ for 3h-12 h, to obtain the original ceramic powder in which the base phase, the dispersed phase and the modified silicate glass ceramic powder are uniformly mixed, and then the mixed original powder is subjected to spherical granulation treatment; when the spherical granulation treatment is performed first and then mixed, the mixing process of the granulated powder is as follows: using the ordinary dry ball milling method, the spherical base phase and dispersed phase powders, and the modified silicate glass ceramic powder are placed in a common ball milling jar in proportion, and ball milled for 3 hours at a ball-to-material ratio of 1:0.1:0.2 and a rotation speed of 150r / min to obtain a uniformly mixed spherical granulated ceramic powder.

[0039] The spherical granulation method in step 4 is electrospray granulation or spray granulation, more preferably electrospray granulation;

[0040] The particle size of the spherical composite powder feed described in step 4 is 1-100 μm.

[0041] The plasma spraying parameters in step 4 are: current 500A-700A, main airflow 30-55slpm, auxiliary airflow 3-10slpm, carrier airflow 1slpm-5slpm, and powder feeding rate 1-5rpm. In step 5, high-temperature sintering is performed using staged temperature control: first, the temperature is raised to 800°C at 10°C / min for debinding, and then raised to the target temperature at 5°C / min.

[0042] The final coating structure in step 5 includes (from substrate to surface): bonding layer (20-200 μm), glass-ceramic intermediate layer (10-50 μm), and gradient functional surface layer (50-500 μm); the thermal conductivity of the coating is less than 0.8 W / (m·K), the bonding strength is greater than 35 MPa, and the fracture toughness is greater than 4.0 MPa·m 1 / 2 , infrared reflectivity>0.85.

[0043] In step 5, the high-temperature sintering is divided into two steps: the first stage is to raise the temperature from 10°C to 800°C for 1 hour to fully remove organic matter; the second stage is to raise the temperature from 5°C to 1250°C for 1 hour to form a densified interface; more preferably, the first stage is to raise the temperature to 800°C for 0.5 hour, and the second stage is to raise the temperature to 1200°C for 0.5 hour;

[0044] 3. The technical principles of the present invention are as follows:

[0045] The technical principle of this invention is based on the collaborative design of multi-scale composite structures and functional gradients, and is specifically achieved through the following key innovations:

[0046] 1. Nano-reinforcement and self-healing mechanism of glass-ceramic interlayer: Yb2O3, nanoparticles, and Al2O3 chopped fibers are introduced into the silicate glass matrix using a sol-gel method to form a nano-micrometer multi-scale reinforcement phase. Yb2O3 inhibits crack propagation by pinning grain boundaries, while Al2O3 fibers provide bridging toughening, increasing the fracture toughness of the interlayer to 3.5 MPa·m 1 / 2 During the high-temperature sintering process, the silicate glass phase softens and flows at 1000-1250°C, filling the microcracks in the coating, forming a self-healing network, and realizing dynamic repair of cracks.

[0047] 2. Low thermal conductivity and radiation resistance design of the gradient functional surface layer: Y2NbO7 or RE2Zr2O7 is selected as the base phase, and the high phonon scattering of the fluorite structure is used to reduce the lattice thermal conductivity. GdTaO4 and a microporous structure are introduced into the dispersed phase with an equivalent radius of 0.5-5μm. The high infrared reflectivity (reflectivity >0.85 in the 0.3-10μm band) is used to inhibit radiative heat transfer. At the same time, the micropores further reduce the effective thermal conductivity to below 0.8W / (m·K). The gradient ratio design is designed, and the volume fraction of each dispersed phase increases by 5-15%, so that the thermal expansion coefficient transitions smoothly from the middle layer to the surface layer, with a thermal expansion coefficient difference of <1.2×10 -6 / K, avoid interface stress concentration.

[0048] 3. Coordinated optimization of plasma spraying and high-temperature sintering processes: Through step-by-step gradient spraying, the dispersed phase gradient increases, combined with segmented temperature-controlled sintering, first debinding and then densification, to achieve a continuous change in coating composition from the substrate to the surface and a densified interface, with a porosity of <8%; during the high-temperature sintering process, the intermediate layer glass phase and the surface layer oxide partially diffuse to form a chemically bonded interface, and the bonding strength is increased to above 35MPa.

[0049] 3. Technical Effects of the Invention

[0050] 1. Comprehensive performance breakthrough: Ultra-low thermal conductivity: Micropores in the gradient surface layer, with a porosity of 8-20%, work synergistically with the high infrared reflective phase, GdTaO4, to achieve an overall thermal conductivity of <0.8W / (m·K), which is more than 65% lower than that of traditional YSZ coatings; High toughness: The middle layer of nano-Yb2O3 and Al2O3 fiber toughening results in a fracture toughness of 4.0MPa·m 1 / 2 , relatively pure glass ceramics (≈2.5MPa·m 1 / 2 ) increased by 60%, thermal shock cycle life> 200 times (1200℃ to room temperature water quenching); radiation resistance: the infrared reflectivity of the functional surface layer in the 0.3-10μm band is> 0.85, and the radiation heat flux attenuation rate is> 70%, which significantly reduces high-temperature radiation heat transfer.

[0051] 2. Improved interface reliability: The gradient structure design reduces interface thermal stress by approximately 50%, with a bonding strength >35MPa (traditional multi-layer coating ≈25MPa), and no interface delamination after thermal exposure at 1200°C / 100h.

[0052] 3. Self-healing ability: The fluidity of the glass phase in the middle layer is enhanced at 1200°C, and micro-cracks with a width of ≤10μm can be healed within 30 minutes, extending the coating life to more than twice that of traditional coatings.

[0053] 4. Process compatibility: Plasma spraying and conventional sintering processes are used, without the need for complex equipment (such as EB-PVD). The preparation cost is about 80% lower than that of precious metal-doped coatings, making it suitable for industrial mass production.

[0054] Conclusion: Through material system innovation and structure-process collaborative design, this invention solves the problems of traditional thermal barrier coatings such as high thermal conductivity, easy interface failure, and insufficient toughness in ultra-high temperature environments, providing a reliable thermal protection solution for the hot end components of high-end equipment such as aircraft engines and gas turbines. DETAILED DESCRIPTION

[0055] Example 1

[0056] The preparation method of Y3NbO7-GdTaO4 high-toughness and low-conductivity radiation thermal barrier coating is completed in the following steps: Step 1. Pretreatment of substrate surface: first remove the oxide film and grease on the substrate surface, then roughen the substrate surface, and finally perform thermal spray preheating on the substrate surface; the substrate described in step 1 is a high-temperature nickel-based alloy (GH4061); the method for removing the oxide film and grease on the substrate surface in step 1 is: first use sandpaper to polish the substrate, and then use anhydrous ethanol to remove the oil stain on the surface; the method for roughening the substrate surface in step 1 is: at a pressure of 0.3MPa, use 45# corundum sand to sandblast the substrate to obtain a pretreated substrate, and the surface roughness of the substrate is 2μm; the temperature of the thermal spray preheating in step 1 is 800℃; Step 2. Preparation of bonding layer: use atmospheric plasma spraying process to powder the bonding layer. The bonding layer powder in step 2 is NiCrAlY. The atmospheric plasma spraying process in step 2 is as follows: the current is 580A, the main air flow is 40slpm, the auxiliary air flow is 3.5slpm, the carrier air flow is 3.2slpm, and the powder feeding rate is 3rpm. The thickness of the bonding layer on the substrate with the bonding layer in step 2 is 80μm. Step 3. Preparation of glass ceramic intermediate layer: The modified silicate glass ceramic powder is mixed with the oxide dispersed phase and the base phase ceramic, and the intermediate layer is formed by plasma spraying. In step 3, Y2O3 and Nb2O5 are reacted in the solid phase to obtain Y3NbO7. Gd2O3 and Ta2O5 are reacted in the solid phase to obtain GdTaO4. In step 3, the refractive index n of GdTaO4 is 2.1, and the refractive index n of Y3NbO7 is 1.7. The thermal expansion coefficient of GdTaO4 is 11.2×10 -6 K -1 The thermal expansion coefficient of the base phase ceramic Y3NbO7 is 11×10 -6 K -1; The thermal conductivity of GdTaO4 is 1.7W / (m·K), and the thermal conductivity of Y3NbO7 is 1.5W / (m·K); GdTaO4 is a monoclinic crystal system, and Y3NbO7 belongs to a cubic crystal system, and there is no infinite solid solution effect between the two phases; GdTaO4 has ferroelastic phase transition characteristics; the original particle size of GdTaO4 is 1μm, and the original particle size of the base phase ceramic Y3NbO7 is 3μm; Step 4. Preparation of gradient functional surface: weigh the ceramic base phase component, the dispersed phase functional ceramic component, and the modified silicate glass ceramic powder in proportion, and then mix the weighed ceramic base phase component, the dispersed phase functional ceramic component, and the modified silicate glass ceramic powder for powder mixing and spherical The mixed powder is granulated and spherical to obtain a spherical mixed powder feed; the molar ratio of the ceramic matrix phase component, the dispersed phase functional ceramic component, and the modified silicate glass ceramic powder in step 4 is 5:1:3; in step 4, the powder is first mixed and then spherical granulated, and the mixing process is as follows: the mixed powder, anhydrous ethanol and zirconium oxide balls are placed in a planetary ball mill at a mass ratio of 1:0.1:3, and ball milled at a speed of 300r / min for 8h to obtain a slurry, and then the slurry is dried at 100°C for 8h to obtain a mixed ceramic powder; the process of spherical granulation is to use electrospray granulation, which is specifically completed in the following steps: ① Preparation of electrospray slurry: Mix the mixed ceramic powder Dispersed in an aqueous dispersant, then ultrasonicated for 50 minutes, then added with a pore-forming agent, and heated and stirred in a water bath at 60°C for 12 hours to obtain a uniform electrospray slurry; the aqueous dispersant described in step ① is N-methylpyrrolidone; the pore-forming agent described in step ① is polyethersulfone; the mass ratio of the mixed ceramic powder to the pore-forming agent described in step ① is 3:1; the mass ratio of the mixed ceramic powder to the aqueous dispersant described in step ① is 1:1; ② electrospray granulation: load the electrospray slurry into an electrospray syringe with a positive voltage, the needle tip voltage is 20kV, the needle size is 0.5mm, the discharge rate is 0.5mg / s, and the receiving container is deionized water to obtain a suspension. Suspension; ③ post-processing of microspheres: filter the suspension, and then dry the solid matter at 120°C for 8h to obtain a dry spherical granulation powder; calcine the dried spherical granulation powder at 1200°C for 6h to obtain a spherical porous electrospray granulation feed powder; the particle size of the spherical porous electrospray granulation feed powder is about 28μm, and the porosity is 20%; adopt the plasma spraying method to spray the spherical mixed powder feed onto the surface of the substrate with the bonding layer, and prepare a high-toughness, low-conductivity radiation functional surface layer on the surface of the substrate; in step 5, sinter at 1200°C for 1 hour to obtain the Y3NbO7-GdTaO4Y3 high-toughness, low-conductivity radiation thermal barrier coating.

[0057] The parameters of the plasma spraying described in step 4 are: current 550A, main airflow 45slpm, auxiliary airflow 3.3slpm, carrier airflow 3.2slpm, and powder feeding rate 3rpm; the thickness of the functional surface layer of high-toughness and low-conductivity radiation heat penetration described in step 4 is 220μm; the functional surface layer of the high-toughness and low-conductivity radiation thermal barrier coating described in step 4 has a dispersed particle system structure, that is, the micropores and the functional dispersed phase are uniformly distributed in the base phase ceramic, that is, the micropores with an average equivalent radius of 2μm and the G with an average equivalent radius of 5μm. dTaO4 is dispersed in Y3NbO7, the porosity of the coating is 11%, and the volume fraction of the coating occupied by micropores and GdTaO4 is 27%; in step 5, the high-temperature sintering is 1200°C for 1 hour, and the high-toughness and low-conductivity radiation thermal barrier coating obtained has a thermal conductivity of 0.25W / (m·K), a bonding strength with the substrate of 39MPa, a hardness of 5Gpa, a fracture toughness of 4.2MPa·m1 / 2, an infrared reflectivity of 1.3 in the 0.3-10μm band, and an infrared transmittance of less than 0.1.

[0058] The spherical porous electrospray granulation feed powder prepared in step 4 of Example 1 has a good spherical structure, a size of 28 μm, and a porous structure.

[0059] In this example, an LFA457 laser thermal conductivity meter was used to measure the thermal conductivity of the Y3NbO7-GdTaO4 integrated thermal barrier ceramic coating with high strength, toughness, low thermal conductivity, and resistance to thermal radiation penetration, prepared in step 5 of this example. The results showed that the thermal conductivity of the Y3NbO7-GdTaO4 integrated thermal barrier ceramic coating with high strength, toughness, low thermal conductivity, and resistance to thermal radiation penetration, prepared in step 5, was 0.25 W / (m·K) at 1000°C.

[0060] The Y3NbO7-GdTaO4 high-toughness, low-conductivity radiation thermal barrier coating prepared in step 5 of Example 1 has good bonding strength with the substrate, with a bonding strength of 39 MPa. At the same time, the coating has excellent thermal shock resistance, and the number of thermal shock cycles at room temperature and 1200°C is greater than 50 times, thereby proving that the Y3NbO7-GdTaO4 high-toughness, low-conductivity radiation thermal barrier coating prepared in step 5 of Example 1 prepared in this example has excellent thermal protection performance.

[0061] The preparation method of the modified silicate glass ceramic powder in step 3 above is as follows, in parts by weight:

[0062] S1. Raw material pretreatment: 60 parts of silicate glass powder, 10 parts of Yb2O3 nanoparticles, and 15 parts of Al2O3 chopped fibers were mixed;

[0063] Sol-gel coating: The S1 mixed powder was dispersed in a tetraethyl orthosilicate solution with a volume ratio of 2:3:1 between tetraethyl orthosilicate and ethanol and water. 0.1 mol / L HNO3 catalyst was added and ultrasonically stirred for 1 hour to form a sol. The mixture was then gelled in a 70°C water bath for 3 hours to obtain a nano-SiO2-coated composite gel powder.

[0064] S3 heat treatment: The resulting composite gel powder S2 was calcined at 600 ° C for 1 hour to remove organic matter, and then annealed at 1100 ° C for 1 hour to form a nano-Yb2O3-Al2O3 fiber-reinforced glass ceramic powder;

[0065] Wherein, in the above S1 and S2, the quantitative ratio between the mass of the mixed powder (unit: g) and the volume of the ethyl orthosilicate solution (unit: ml) is 1:5;

[0066] Example 2

[0067] The preparation method of YSZ-NdAlO3 high-toughness and low-conductivity radiation thermal barrier coating is completed in the following steps: Step 1. Substrate surface pretreatment: first remove the oxide film and grease on the substrate surface, then roughen the substrate surface, and finally perform thermal spray preheating on the substrate surface; the substrate described in step 1 is a SiC substrate; the method for removing the oxide film and grease on the substrate surface in step 1 is: first polish the substrate with sandpaper, and then use anhydrous ethanol to remove the oil stain on the surface; the method for roughening the substrate surface in step 1 is: laser texturing, process parameters are: laser power of 5kW, pulse frequency of 15Hz, spot size of 15μm, and the roughness of the obtained texturing substrate surface is 3μm; the temperature of the thermal spray preheating in step 1 is 900℃; Step 2. Preparation of bonding layer: the bonding layer powder is sprayed by atmospheric plasma spraying. Sprayed onto the surface of the workpiece to obtain a substrate with a bonding layer; the bonding layer powder described in step 2 is Hf-Si; the atmospheric plasma spraying process described in step 2 is: current 600A, main airflow 45slpm, auxiliary airflow 3.5slpm, carrier airflow 3.5slpm, and powder feeding rate 2.8rpm; the thickness of the bonding layer on the substrate with the bonding layer described in step 2 is 100μm; step 3. Preparation of glass ceramic intermediate layer: modified silicate glass ceramic powder is mixed with oxide dispersed phase and base phase ceramic, and an intermediate layer is formed by plasma spraying. In step 3, Nd2O3 and Al2O3 are used to obtain NdAlO3 by solid phase reaction; YSZ is a commercial oxidation-stabilized zirconia ceramic; the refractive index n of NdAlO3 in step 3 is 1.95, and the refractive index n of YSZ is 2.15; the thermal expansion coefficient of NdAlO3 is 10.3×10 -6 K -1 , the thermal expansion coefficient of YSZ is 10.9×10 -6 K-1, the thermal conductivity of NdAlO3 is 3.8W / (m·K), the thermal conductivity of YSZ is 2.3W / (m·K), NdAlO3 is an orthorhombic crystal system, YSZ belongs to a cubic crystal system, and there is no infinite solid solution effect between the two phases; NdAlO3 has ferroelastic phase transition characteristics; the original particle size of NdAlO3 is 1.5μm, and the original particle size of YSZ is 5μm; Step 4. Preparation of gradient functional surface: weigh the ceramic matrix phase components and the dispersed phase functional ceramic components and the modified silicate glass ceramic powder in proportion, and then spherical granulate the weighed ceramic matrix phase components and the dispersed phase functional ceramic components and the modified silicate glass ceramic powder, and then mix them to obtain a spherical composite powder feed; the ceramic matrix phase components and the dispersed phase described in step 4 The molar ratio of the functional ceramic component and the modified silicate glass ceramic powder is 3:1:2; the granulation method of the ceramic matrix phase component described in step 4 is electrospray granulation, and the granulation method of the dispersed phase functional ceramic component is spray drying granulation; the granulation method of the ceramic matrix phase component described in step 4 is electrospray granulation, which is specifically completed according to the following steps: ① Preparation of electrospray slurry: YSZ powder and polyethersulfone pore-forming agent are dissolved in N-methylpyrrolidone in a mass ratio of 4:1, ultrasonicated for 50 minutes, and heated in a water bath at 60°C with stirring for 12 hours to obtain a uniform electrospray slurry; the mass ratio of YSZ powder to N-methylpyrrolidone described in step ① is 1:1.2; ② Electrospray granulation: the electrospray slurry is loaded into an electrospray needle with a positive voltage. In the cylinder, the needle tip voltage is 20kV, the needle size is 0.76mm, the discharge speed is 0.5mg / s, and the receiving container is deionized water to obtain a suspension; ③ post-processing of microspheres: the suspension is filtered, and the solid matter is dried at 100°C for 12h to obtain a dry spherical granulation powder; the dried spherical granulation powder is calcined at 1200°C for 4h to obtain a spherical porous YSZ electrospray granulation feed powder; the particle size of the spherical porous YSZ electrospray granulation feed powder is about 50μm and the porosity is 18%; the granulation method of the dispersed phase functional ceramic component NdAlO3 is spray drying granulation, which is specifically completed in the following steps: phenylacetic acid, polyvinyl alcohol and NdAlO3 ceramic powder are mixed according to the reaction mixture. The slurry is dispersed in deionized water in a mass ratio of 1:1:4 to obtain a slurry with a solid content of 30%. The slurry is then spray-granulated at a hot air velocity of 0.5 m / s, a temperature of 160°C, and a spray pump pressure of 3 MPa to obtain a spherical NdAlO3 feed powder. The modified silicate glass ceramic powder is granulated in the same manner as the dispersed phase functional ceramic component NdAlO3. In step 4, the spherical porous YSZ electrospray granulation feed powder and the spherical NdAlO3 feed powder are mixed by conventional ball milling. Specifically, the spherical porous YSZ electrospray granulation feed powder and the spherical NdAlO3 feed powder are weighed in a mass ratio of 1:3. ZrO2 balls are then added to the mixed feed powder at a ball-to-material ratio of 1:0.The spherical composite powder feed was placed in a conventional ball mill and milled at 150 rpm for 3 hours to obtain a spherical composite powder feed. The spherical composite powder feed was then sprayed onto the surface of the substrate with the bonding layer using a plasma spraying method to form a high-toughness, low-conductivity, and radiation-resistant thermal barrier coating on the substrate surface. In step 5, the sintering was performed at 1200°C for 1 hour to obtain a YSZ-NdAlO3 high-toughness, low-conductivity, and radiation-resistant thermal barrier coating.

[0068] The parameters of the plasma spraying described in step 4 are: current of 600A, main airflow of 45slpm, auxiliary airflow of 3.5slpm, carrier airflow of 3.2slpm, and powder feeding rate of 3rpm; the thickness of the functional surface layer of high toughness and low conductivity radiation heat penetration described in step 4 is 220μm; the functional surface layer of high toughness and low conductivity radiation heat penetration described in step 4 has a dispersed particle system structure, that is, the micropores and the functional dispersed phase are uniformly distributed in the base phase ceramic, that is, the micropores with an average equivalent radius of 1.5μm and the functional dispersed phase with an average equivalent radius of 3.5μm The NdAlO3 is dispersed in the YSZ composition, the porosity of the coating is 9%, and the volume fraction of the coating occupied by micropores and NdAlO3 is 24%; the high-temperature sintering in step 5 is sintering at 1200℃ for 1 hour, and the thermal conductivity of the high-toughness and low-conductivity radiation thermal barrier coating obtained is 0.56W / (m·K), the bonding strength with the substrate is 28Mpa, the hardness is 3.2Gpa, the fracture toughness is 3.7MPa·m1 / 2, the infrared reflectivity in the 0.3-10μm band is 0.63, and the infrared transmittance is less than 0.1. This embodiment uses a Fourier spectrometer to test the spectral response characteristics of the YSZ-NdAlO3 high-toughness and low-conductivity radiation coating prepared in step 5 of this embodiment. The measurement results show that the reflectivity of the YSZ-NdAlO3 high-toughness and low-conductivity radiation coating prepared in step five of this embodiment is 0.95 in the 0.3-10μm band.

[0069] In this example, an LFA457 laser thermal conductivity meter was used to measure the thermal conductivity of the YSZ-NdAlO3 high-toughness, low-conductivity radiation-exposed coating prepared in step 5 of this example. The results showed that the thermal conductivity of the YSZ-NdAlO3 high-toughness, low-conductivity radiation-exposed coating prepared in step 5 was 0.56 W / (m·K) at 1000°C.

[0070] The YSZ-NdAlO3 high-toughness, low-conductivity radiation coating prepared in step 5 of Example 2 has good bonding strength with the substrate, with a bonding strength of 23 MPa. At the same time, the coating has excellent thermal shock resistance, and the number of thermal shock cycles at room temperature and 1200°C is greater than 50 times, which proves that the YSZ-NdAlO3 high-toughness, low-conductivity radiation coating prepared in this example has excellent thermal protection performance.

[0071] The modified silicate glass ceramic powder is the same as that in Example 1;

[0072] Comparative Example 1:

[0073] The preparation method of the ceramic coating of Al2O3 doped with Y3NbO7 is completed in the following steps: Step 1. Pretreatment of the substrate surface: first, removing the oxide film and grease on the substrate surface, then roughening the substrate surface, and finally performing thermal spray preheating on the substrate surface; the substrate described in step 1 is a high-temperature nickel-based alloy (GH4061); the method for removing the oxide film and grease on the substrate surface in step 1 is: first, using sandpaper to polish the substrate, and then using anhydrous ethanol to remove the oil stain on the surface; the method for roughening the substrate surface in step 1 is: using 45# corundum sand to sandblast the substrate at a pressure of 0.3MPa to obtain a pretreated substrate, and the surface roughness of the substrate is 2μm; the temperature of the thermal spray preheating in step 1 is 800℃; Step 2. Preparation of the bonding layer: using the atmospheric plasma spraying process to spray the bonding layer powder onto the workpiece. The surface of the component is sprayed with a bonding layer to obtain a substrate with a bonding layer; the bonding layer powder in step 2 is NiCrAlY; the atmospheric plasma spraying process in step 2 is as follows: current 580A, main air flow 40slpm, auxiliary air flow 3.5slpm, carrier air flow 3.2slpm, powder feeding rate 3rpm; the thickness of the bonding layer on the substrate with a bonding layer in step 2 is 80μm; step 3. preparation of a glass ceramic intermediate: a ceramic matrix component Y3NbO7 is prepared by a solid phase reaction method, and Al2O3 is selected as the dispersed phase functional ceramic component; in step 3, Y2O3 and Nb2O5 are solid-phase reacted to obtain Y3NbO7; commercial Al2O3 is used; the refractive index n of Al2O3 in step 3 is 1.75, and the refractive index n of Y3NbO7 is 1.7 (the difference in dielectric function between the two is too small); the thermal expansion coefficient of Al2O3 is 7.45×10 - 6 K -1 The thermal expansion coefficient of Y3NbO7 is 11×10 -6 K -1(The expansion coefficients of the two are not matched); the thermal conductivity of Al2O3 is 7.8W / (m·K), and the thermal conductivity of Y3NbO7 is 1.5W / (m·K) (the thermal conductivity of Al2O3 is too large); Al2O3 belongs to the hexagonal crystal system, and Y3NbO7 belongs to the cubic crystal system. There is no infinite solid solution effect between the two phases; Al2O3 does not have ferroelastic phase transition characteristics (it cannot play a ferroelastic toughening effect); the original particle size of Al2O3 is 1μm, and the original particle size of Y3NbO7 is 3μm; Step 4. Preparation of gradient functional surface: weigh the ceramic matrix phase components and dispersed phase functional ceramic components, and modified silicate glass ceramic powder in proportion, and then weigh The ceramic matrix phase component, the dispersed phase functional ceramic component, and the modified silicate glass ceramic powder are powder-mixed and spheroidized to obtain a spherical mixed powder feed; the molar ratio of the ceramic matrix phase component, the dispersed phase functional ceramic component, and the modified silicate glass ceramic powder in step 4 is 5:1:1; in step 4, the powders are first mixed and then spheroidized, and the mixing process is as follows: the mixed powder, anhydrous ethanol, and zirconium oxide balls are placed in a planetary ball mill at a mass ratio of 1:0.1:3, and ball-milled at a speed of 300 r / min for 8 hours to obtain a slurry; the slurry is dried at 100° C. for 6 hours to obtain a ball-milled mixed powder; The mixed powder after ball milling is electrospray granulated, which is completed in the following steps: ① Preparation of electrospray slurry: dissolving the mixed powder after ball milling and polyethersulfone pore-forming agent in N-methylpyrrolidone at a mass ratio of 3:1, ultrasonicating for 50 minutes, and heating and stirring in a water bath at 60°C for 12 hours to obtain a uniform electrospray slurry; the mass ratio of the mixed powder after ball milling and N-methylpyrrolidone described in step ① is 1:1; ② Electrospray granulation: loading the electrospray slurry into an electrospray syringe with a positive voltage, the needle tip voltage is 20kV, the needle size is 0.5mm, the discharge rate is 0.5mg / s, and deionized water is selected as the receiving container to obtain a suspension liquid; ③ microsphere post-processing: filtering the suspension, and then drying the solid matter at 120°C for 8 hours to obtain a dry spherical granulation powder; calcining the dried spherical granulation powder at 1200°C for 6 hours to obtain a spherical porous electrospray granulation feed powder; the spherical porous electrospray granulation feed powder has a particle size of about 26 μm and a porosity of 19%; using a plasma spraying method, the spherical mixed powder feed is sprayed onto the surface of a substrate with a bonding layer to prepare a high-toughness, low-conductivity irradiation functional surface layer on the substrate surface; in step 5, the Al2O3-doped Y3NbO7 ceramic coating is obtained by high-temperature sintering at 1200°C for 1 hour.

[0074] The plasma spraying process in step 4 is as follows: current of 550A, main airflow of 45slpm, auxiliary airflow of 3.3slpm, carrier airflow of 3.2slpm, and powder feeding rate of 3.5rpm; the thickness of the surface layer in step 2 is 220μm; the Al2O3-doped Y3NbO7 ceramic coating in step 4 is composed of micropores with an average equivalent radius of 1.8μm and Al2O3 with an average equivalent radius of 4μm dispersed in Y3NbO7, the porosity of the coating is 10%, and the volume fraction of the micropores and Al2O3 in the coating is 25%; in this embodiment, a Fourier spectrometer is used to test the spectral response characteristics of the Al2O3-doped Y3NbO7 ceramic coating prepared in step 5 of this embodiment. The measurement results show that the reflectivity of the Al2O3-doped Y3NbO7 ceramic coating prepared in step 5 of this embodiment is 0.65 in the 0.5-10μm band.

[0075] In this example, an LFA457 laser thermal conductivity meter was used to measure the thermal conductivity of the Al2O3-doped Y3NbO7 ceramic coating prepared in step 5 of this example. The results showed that the thermal conductivity of the Al2O3-doped Y3NbO7 ceramic coating prepared in step 5 was 1.3 W / (m·K) at 1000°C.

[0076] The Al2O3-doped Y3NbO7 ceramic coating described in step 5 has a thermal conductivity of 1.3 W / (m·K), a bonding strength with the substrate of 27 MPa, a hardness of 1.9 GPa, a fracture toughness of 2.4 MPa·m1 / 2, an infrared reflectivity of 0.76 in the 0.3-10 μm band, and an infrared transmittance of 0.29.

[0077] The modified silicate glass ceramic powder is the same as that in Example 1;

[0078] Comparative Examples 1-2 and Comparative Example 1, the reasons why the high-toughness, low-conductivity radiation thermal barrier coating prepared in Example 1 of the present invention has low thermal conductivity, high bonding strength, high fracture toughness, and high infrared reflectivity of 1.0 in the 0.3-10μm band may be: 1. Coordinated design of low thermal conductivity-high reflectivity material system (Y3NbO7-GdTaO4); 2. Toughening mechanism of gradient structure and nano-reinforced phase (Yb2O3 / Al2O3 fiber); 3. Dynamic repair ability of ferroelastic phase transition and self-healing network; 4. Precise control of pore structure by electrospray granulation process.

Claims

1. A method for preparing a high-toughness and low-conductivity radiation thermal barrier coating, characterized in that: The preparation method is completed according to the following steps: Step 1. Substrate surface pretreatment: first remove the oxide film and grease on the substrate surface, then roughen the substrate surface, and finally perform thermal spray preheating on the substrate surface; Step 2. Prepare the bonding layer: spray the bonding layer powder onto the workpiece surface using an atmospheric plasma spraying process to obtain a substrate with the bonding layer; Step 3. Preparation of glass-ceramic intermediate layer: Modified silicate glass-ceramic powder is mixed with oxide dispersion and formed into an intermediate layer by plasma spraying with a thickness of 10-50 μm; Step 4. Preparation of gradient functional surface layer: The silicate glass ceramic powder modified in step 3 above; Base phase component: low thermal conductivity ceramic, thermal conductivity <3W / (m·K); Dispersed phase: functional ceramics, thermal conductivity <5W / (m·K), and microporous structure; Mix the base phase, dispersed phase, and modified silicate glass ceramic powder in a gradient ratio, granulate them into spherical particles, and then spray them multiple times. Use plasma spraying to spray the spherical composite feed onto the surface of the substrate with the bonding layer. The volume fraction of the dispersed phase increases by 5-15% in each layer, and the final surface layer thickness is 50-500μm. Step 5. High temperature sintering: Keep the temperature at 1000-1250°C for 0.5-2.0 hours to form a densified interface and a glass phase self-healing network to obtain a high-toughness, low-conductivity radiation thermal barrier coating.

2. The method for preparing a high-toughness, low-conductivity radiation thermal barrier coating according to claim 1, characterized in that: In the above step 4, the base phase component is at least one of Y3NbO7, RE2Zr2O7 or modified YSZ; the dispersed phase is at least one of GdTaO4, Al2O3 or doped rare earth zirconate.

3. The method for preparing a high-toughness, low-conductivity radiation thermal barrier coating according to claim 1, characterized in that: The substrate described in step 1 is a metal-based material or a ceramic-based material; the metal-based material is a titanium-aluminum alloy, a nickel-based alloy or a niobium-based alloy; the ceramic-based material is C / C, SiC / SiC, C / SiC or ZrB2-SiC; the method for removing the oxide film and grease on the surface of the substrate in step 1 is to use sandpaper to polish the substrate to remove the oxide film, and then use one or more of solvent cleaning, steam cleaning, alkaline cleaning and heating degreasing methods to remove the substrate grease; the method for roughening the substrate surface in step 1 is Sandblasting or laser texturing: sandblasting is used when the substrate is a metal-based material, and laser texturing is used when the substrate is a ceramic-based material; the sandblasting parameters are: sand particle size of 15-50, sandblasting pressure of 0.3-0.7 MPa; the laser texturing parameters are: laser power of 1-8 kW, pulse frequency of 10-20 Hz, spot size of 10-100 μm, and the roughness of the resulting texturized substrate surface is 1-5 μm; the thermal spray preheating temperature in step 1 is 600-900°C.

4. The method for preparing a high-toughness, low-conductivity radiation thermal barrier coating according to claim 1, characterized in that: The bonding layer powder described in step 2 needs to be selected according to the type of substrate. When the substrate is a metal-based material, the bonding layer powder is MCrAlY, where M is Ni, Co or NiCo; when the substrate is laser-textured, the bonding layer powder is RE-Si, where RE is a rare earth element, and the rare earth element is Hf or Y. The atmospheric plasma spraying process described in step 2 is: current 600A-650A, main airflow 40-50slpm, auxiliary airflow 3-10slpm, carrier airflow 1slpm-5slpm, and powder feeding rate 1-3rpm; the thickness of the bonding layer on the substrate with the bonding layer described in step 2 is 20μm-200μm.

5. The method for preparing a high-toughness and low-conductivity radiation thermal barrier coating according to claim 1, characterized in that: The preparation method of the modified silicate glass ceramic powder in step 3 is as follows: S1. Raw material pretreatment: Mixing silicate glass powder with Yb2O3 nanoparticles and Al2O3 chopped fibers in a mass ratio of (40-70): (5-15): (10-20); S2. Sol-gel coating: The S1 mixed powder was dispersed in a tetraethyl orthosilicate solution, wherein the volume ratio of tetraethyl orthosilicate to ethanol and water was (1-3): (2-5): (1-2), and 0.1 mol / L HNO3 catalyst was added and ultrasonically stirred for 1-2 hours to form a sol; gelation was carried out in a water bath at 70-80 ° C for 2-4 hours to obtain a nano-SiO2-coated composite gel powder; S3 heat treatment: S2 the resulting composite gel powder was calcined at 400-600 ℃ for 2-3 hours to remove organic matter, and then annealed at 1000-1100 ℃ for 1-2 hours to form a nano-Yb2O3-Al2O3 fiber-reinforced glass ceramic powder; Among them, in the above S1 and S2, the quantitative ratio between the mass of the mixed powder (unit: g) and the volume of the ethyl orthosilicate solution (unit: ml) is 1:

5.

6. The method for preparing a high-toughness, low-conductivity radiation thermal barrier coating according to claim 1, characterized in that: The softening temperature of the silicate glass ceramic in step 3 is ≥1000°C, the mass ratio of the silicate glass ceramic to the oxide dispersed phase YSZ or Al2O3 is 7:3, and the porosity of the intermediate layer is 5-15%; the expansion coefficient of the base phase and the dispersed phase in step 4 is less than 1.2×10 -6 K -1 .

7. The method for preparing a high-toughness, low-conductivity radiation thermal barrier coating according to claim 1, characterized in that: In the gradient functional surface layer of step 4, the micropore equivalent radius is 0.5-5 μm, the dispersed phase particle size is 0.3-10 μm, and the overall porosity of the surface layer is 8-20%.

8. The method for preparing a high-toughness, low-conductivity radiation thermal barrier coating according to claim 1, characterized in that: The molar ratio of the ceramic matrix phase component, the dispersed phase functional ceramic component, and the modified silicate glass ceramic powder described in step 4 is (3-20): 1: (1-5); the process of powder mixing and spherical granulation treatment described in step 4 does not distinguish between the order of priority; when the powder mixing is performed first and then the spherical granulation treatment is performed, the mixing process is as follows: a certain proportion of the matrix phase and dispersed functional phase original powder, the modified silicate glass ceramic powder, anhydrous ethanol and zirconium oxide balls are placed in a planetary ball mill in a mass ratio of 1:0.1:3, and the mixture is pulverized at 200r / min-400r / mi n for 6h-12h to obtain a raw powder mixed slurry, and then dry the slurry at 60℃-120℃ for 3h-12h to obtain a raw ceramic powder in which the base phase and the dispersed phase are uniformly mixed with the modified silicate glass ceramic powder, and then the mixed raw powder is sphericalized and granulated; when the spherical granulation is performed first and then mixed, the mixing process of the granulated powder is as follows: using ordinary dry ball milling method, the spherical base phase and dispersed phase powders, and the modified silicate glass ceramic powder are placed in an ordinary ball mill according to proportion, and ball milled for 3h at a ball-to-material ratio of 1:0.1 and a rotation speed of 150r / min to obtain a uniformly mixed spherical granulated ceramic powder.

9. The method for preparing a high-toughness, low-conductivity radiation thermal barrier coating according to claim 1, characterized in that: The spherical granulation method described in step 4 is electrospray granulation or spray granulation; the electrospray granulation steps are as follows: ① Preparation of electrospray slurry: Disperse the mixed ceramic powder in an aqueous dispersant, then ultrasonicate for 30-100 minutes, then add a pore-forming agent, and heat and stir in a water bath at 40-70°C for 6-18 hours to obtain a uniform electrospray slurry; the aqueous dispersant described in step ① is one or both of polyvinyl pyrrolidone and N-methyl pyrrolidone; the pore-forming agent described in step ① is polyethersulfone or polytetrafluoroethylene; the mass ratio of the mixed ceramic powder to the pore-forming agent described in step ① is (2-5):1; the mass ratio of the mixed ceramic powder to the aqueous dispersant described in step ① is 1:(0.5-2); ② Electrospray granulation: Load the electrospray slurry into an electrospray syringe with a positive voltage, the needle tip voltage is 10-30kV, and the needle size is 0.5 -2mm, a discharge rate of 0.5-2mg / s, and deionized water is selected as a receiving container to obtain a suspension; ③ microsphere post-treatment: the suspension is filtered, and the solid matter is dried at 60-120°C for 3-24 hours to obtain a dry spherical granulation powder; the dried spherical granulation powder is calcined at 1000-1500°C for 1-6 hours to obtain a spherical porous electrospray granulation feed powder; the spray granulation steps are as follows: phenylacetic acid, polyvinyl alcohol and mixed ceramic powder are dispersed in deionized water in a mass ratio of 1:1:(3-6) to obtain a slurry with a solid content of 20-40%; then, spray granulation is carried out at a hot air speed of 0.3-0.6m / s, a temperature of 100°C-220°C and a spray pump pressure of 1-5MPa to obtain a spray granulation feed powder; the particle size of the spherical composite powder feed described in step 4 is 1-100μm.

10. The method for preparing a high-toughness, low-conductivity radiation thermal barrier coating according to claim 1, characterized in that: The plasma spraying parameters described in step 4 are: current of 500A-700A, main airflow of 30-55slpm, auxiliary airflow of 3-10slpm, carrier airflow of 1slpm-5slpm, and powder feeding rate of 1-5rpm; high-temperature sintering in step 5 adopts segmented temperature control: first increase the temperature to 800℃ for debinding at 10℃ / min, and then increase the temperature to the target temperature at 5℃ / min; the final coating structure in step 5 includes: from the substrate to the surface: the bonding layer is 20-200μm, the glass-ceramic intermediate layer is 10-50μm, and the gradient functional surface layer is 50-500μm; the thermal conductivity of the coating is <0.8W / (m·K), the bonding strength is >35MPa, and the fracture toughness is >4.0MPa·m 1 / 2 , infrared reflectivity>0.85.