An ultra-high temperature thermal environmental barrier coating for silicon carbide substrates, a method of making the same, and a silicon carbide composite substrate

Abstract

The application provides a super-high-temperature thermal environmental barrier coating for a silicon carbide substrate and a preparation method thereof and a silicon carbide composite substrate, and relates to the field of thermal spraying coatings. The super-high-temperature thermal environmental barrier coating for the silicon carbide substrate comprises a gradient transition layer, a bonding layer, a dynamic stress regulation layer and a protective layer which are sequentially stacked; the gradient transition layer comprises Al2O3 and TiC; the bonding layer comprises an Al-Co-Cr-Fe-Ni-Ti-Si-B alloy; the dynamic stress regulation layer comprises a Ni-Ti-Hf alloy; the protective layer comprises Gd-Yb-Sm-Dy-Lu-Zr2O7 and SiC; a microcapsule repair layer is further arranged between the dynamic stress regulation layer and the protective layer, and the microcapsule repair layer comprises a microcapsule repair agent; the microcapsule repair agent comprises a SiC core and a glassy SiO2 arranged on the surface of the SiC core. The coating forms a "buffer-regulation-protection-repair" system through five layers, and solves the problems of interface mismatch and insufficient protection.

Description

Technical Field

[0001] This application relates to the field of thermal spray coatings, and more particularly to an ultra-high temperature thermal environment barrier coating for silicon carbide substrates, a method for preparing the same, and a silicon carbide composite substrate. Background Technology

[0002] Silicon carbide (SiC)-based composites, with their low density, high specific strength, and excellent high-temperature stability, have become core candidate materials for ultra-high temperature hot-end components in the aerospace field (such as turbine engine blades and combustion chamber liners). However, the service environment of such components is extremely harsh: they must not only withstand continuous high-temperature thermal shock above 1400°C, but also resist high-temperature combustion gas erosion, CMAS (calcium magnesium aluminum silicate) molten salt corrosion, and frequent thermal cycling from room temperature to 1500°C. This places multiple key demands on the thermal protective coating on the substrate surface—it must have low thermal conductivity (≤0.7 W / m•K) to effectively block high temperatures, and it must also ensure the structural stability with the SiC substrate and the functional layers inside the coating to avoid substrate ablation or mechanical property degradation due to protective failure.

[0003] To meet these requirements, thermal barrier coating technology has evolved from early single ceramic layers (such as YSZ coatings) to multi-layer composite systems. Typical architectures include a two-layer structure of "adhesive layer + ceramic protective layer" and a three-layer structure of "transition layer + adhesive layer + protective layer". The transition layer often uses ceramic materials such as Al2O3 and TiC, whose core function is to buffer the thermal expansion mismatch between the SiC substrate and the subsequent coating. The adhesive layer is mainly composed of MCrAlY (M=Ni, Co) alloy, used to improve the interfacial bonding between the coating and the transition layer. The protective layer is mainly composed of rare earth zirconates such as Gd2Zr2O7 and Yb2Zr2O7, relying on their high melting point to resist ultra-high temperature corrosion. However, existing multi-layer composite systems still suffer from a fundamental bottleneck of interfacial mismatch failure, severely restricting their performance: on the one hand, traditional transition layers are mostly single homogeneous structures, and the difference in thermal expansion coefficients between the SiC substrate and the adhesive / protective layer often exceeds 1.5 × 10⁻⁶. -6 / K, the tensile and compressive stresses generated at the interface during thermal cycling far exceed the coating bonding strength (≤30MPa). For example, a coating using a single Al2O3 transition layer developed through-cracks after 500 cycles of 1400℃-room temperature. On the other hand, there is a lack of effective stress regulation mechanism between the bonding layer and the protective layer. Although the protective layer has good corrosion resistance due to its high density, its strain tolerance is extremely low and it cannot absorb thermal expansion deformation at high temperatures. The interface is prone to failure due to "rigid collision". More importantly, in environments above 1400℃, the Cr and Fe elements in the bonding layer and the rare earth elements in the protective layer are prone to interdiffusion, forming low-melting-point phases such as CrZrO4. Moreover, traditional coatings have no self-repair capability, and microcracks will quickly expand into macroscopic defects, further aggravating interface deterioration.

[0004] With breakthroughs in the thrust-to-weight ratio of aero-engines, the service temperature of hot-end components will further climb to 1600℃. The interface matching defects of existing coatings have become a core obstacle restricting the engineering application of SiC-based composite materials. Therefore, the industry urgently needs a new coating system that can achieve "smooth transition of thermal expansion gradient, dynamic stress control, and long-term interface stability," and solve the interface matching problem through the collaborative design of multi-layer structures to ensure long-term service reliability in ultra-high temperature environments.

[0005] Therefore, there is an urgent need to provide an ultra-high temperature thermal barrier coating for silicon carbide substrates to solve the above problems. Summary of the Invention

[0006] The purpose of this application is to provide an ultra-high temperature thermal environment barrier coating for silicon carbide substrates, a method for preparing the same, and a silicon carbide composite substrate, in order to solve the above-mentioned problems.

[0007] To achieve the above objectives, the first aspect of this application provides an ultra-high temperature thermal environment barrier coating for silicon carbide substrates, comprising a gradient transition layer, an adhesive layer, a dynamic stress control layer, and a protective layer stacked sequentially.

[0008] The gradient transition layer includes Al2O3 and TiC. The Al2O3 content in the gradient transition layer decreases from the side closer to the silicon carbide substrate to the side closer to the adhesive layer, and the TiC content increases from the side closer to the silicon carbide substrate to the side closer to the adhesive layer.

[0009] The adhesive layer comprises an Al-Co-Cr-Fe-Ni-Ti-Si-B alloy;

[0010] The dynamic stress regulation layer comprises a Ni-Ti-Hf alloy;

[0011] The protective layer comprises Gd-Yb-Sm-Dy-Lu-Zr2O7 and SiC;

[0012] The coefficients of thermal expansion of the gradient transition layer, the adhesive layer, the dynamic stress control layer, and the protective layer increase from the direction closest to the silicon carbide substrate to the direction furthest from the silicon carbide substrate;

[0013] A microcapsule repair layer is further disposed between the dynamic stress regulation layer and the protective layer. The microcapsule repair layer includes a microcapsule repair agent. The microcapsule repair agent includes a SiC core and glassy SiO2 disposed on the surface of the SiC core.

[0014] Optionally, the gradient transition layer includes a first transition layer, a second transition layer, and a third transition layer stacked sequentially, wherein the first transition layer is closer to the silicon carbide substrate, and the third transition layer is closer to the adhesive layer, satisfying at least one of the following conditions:

[0015] A. The coefficient of thermal expansion of the first transition layer is 5.0-5.5×10⁻⁶. -6 / K;

[0016] B. The coefficient of thermal expansion of the second transition layer is 6.0-7.0 × 10⁻⁶. -6 / K;

[0017] C. The coefficient of thermal expansion of the third transition layer is 7.5-8.5×10⁻⁶. -6 / K;

[0018] D. The mass percentage of Al2O3 in the first transition layer is 70-80%, and the mass percentage of TiC is 20-30%.

[0019] E. The mass percentage of Al2O3 in the second transition layer is 50-60%, and the mass percentage of TiC is 40-50%.

[0020] F. The mass percentage of Al2O3 in the third transition layer is 30-40%, and the mass percentage of TiC is 60-70%.

[0021] G. The thickness of the gradient transition layer is 30-50 μm;

[0022] H. The difference in the coefficient of thermal expansion between adjacent layers of the gradient transition layer, the adhesive layer, the dynamic stress control layer, and the protective layer is independently ≤0.5×10⁻⁶. -6 / K.

[0023] Optionally, the ultra-high temperature thermal barrier coating for the silicon carbide substrate satisfies at least one of the following conditions:

[0024] A. The Si and B contents in the adhesive layer gradually decrease along the direction from the side closer to the gradient transition layer to the side closer to the dynamic stress control layer, and the Cr and Fe contents in the adhesive layer gradually increase along the direction from the side closer to the gradient transition layer to the side closer to the dynamic stress control layer.

[0025] B. The surface thermal expansion coefficient of the adhesive layer on the side closest to the gradient transition layer is 7.8-8.3×10⁻⁶. -6 / K, the surface thermal expansion coefficient of the adhesive layer on the side closest to the dynamic stress control layer is 8.5×10. -6 / K;

[0026] C. The rate of change of the coefficient of thermal expansion per micrometer of the adhesive layer is ≤0.01×10⁻⁶. -6 / K;

[0027] D. The adhesive layer includes a honeycomb structure;

[0028] E. The porosity of the adhesive layer is 10-15%;

[0029] F. The thickness of the adhesive layer is 0.5-1.0 mm.

[0030] Optionally, the ultra-high temperature thermal barrier coating for the silicon carbide substrate satisfies at least one of the following conditions:

[0031] A. The thickness of the dynamic stress regulation layer is 50-100 μm;

[0032] B. The Ni-Ti-Hf alloy, based on a total mass of 100%, comprises:

[0033] Ni 48-52%, Ti 33-37%, Hf 13-17%;

[0034] C. The phase transition temperature of the dynamic stress regulation layer is 1400-1600℃;

[0035] D. The strain tolerance of the dynamic stress control layer is ≥6%;

[0036] E. The interfacial bonding strength of the dynamic stress control layer is ≥45MPa;

[0037] F. The coefficient of thermal expansion of the dynamic stress-regulating layer is 8-9 × 10⁻⁶. -6 / K.

[0038] Optionally, the ultra-high temperature thermal barrier coating for the silicon carbide substrate satisfies at least one of the following conditions:

[0039] A. The particle size of SiC in the protective layer is 50-100 nm;

[0040] B. The thickness of the protective layer is 0.8-1.5 mm;

[0041] C. The thermal conductivity of the protective layer is ≤0.7 W / m•K;

[0042] D. The density of the protective layer is ≥98%, and the surface roughness is ≤1μm;

[0043] E. The surface thermal expansion coefficient of the protective layer on the side closest to the dynamic stress control layer is 8.5 × 10⁻⁶. -6 / K, the surface thermal expansion coefficient of the protective layer on the side away from the dynamic stress control layer is 8.8-9.0×10. -6 / K;

[0044] F. The protective layer includes a first protective layer, a second protective layer, and a third protective layer stacked sequentially, wherein the first protective layer is the side closer to the dynamic stress control layer, and the third protective layer is the side farther away from the dynamic stress control layer;

[0045] The first protective layer includes Gd 0.2 Yb 0.2 Sm 0.2 Dy 0.2 Lu 0.2 Zr₂O₇ and SiC;

[0046] The second protective layer includes GdYbSmDyLuZr2O7 and SiC, wherein the mass content of Lu, Yb, Sm and Dy decreases in a gradient from the first protective layer to the third protective layer, and the mass content of Gd increases in a gradient from the first protective layer to the third protective layer.

[0047] The third protective layer comprises SiC and Gd2Zr2O7.

[0048] Optionally, the ultra-high temperature thermal barrier coating for the silicon carbide substrate satisfies at least one of the following conditions:

[0049] A. In the second protective layer, the mass contents of Lu, Yb, and Sm decrease independently from 20% of the total metal content to 0% along the direction from the first protective layer to the third protective layer;

[0050] B. In the second protective layer, the decrease rate of Dy is 0.5 times the decrease rate of Lu;

[0051] C. In the second protective layer, the mass content of Gd increases gradually from 20% to 100% of the total metal content along the direction from the first protective layer to the third protective layer;

[0052] D. The thickness of the first protective layer is 0.2-0.4 mm;

[0053] E. The thickness of the second protective layer is 0.3-0.7 mm;

[0054] F. The thickness of the third protective layer is 0.2-0.4 mm; G. The third protective layer comprises a columnar crystal structure;

[0055] H. The mass content of SiC in the first protective layer, the second protective layer, and the third protective layer is independently 10-20%.

[0056] Optionally, the ultra-high temperature thermal barrier coating for the silicon carbide substrate satisfies at least one of the following conditions:

[0057] A. The particle size of the microcapsule repair agent is 20-50 μm;

[0058] B. The density of the microcapsule repair agent is 5-10 capsules / mm². 2 ;

[0059] C. The purity of the SiC core is ≥99%;

[0060] D. The thickness of the glassy SiO2 is 1-5 μm;

[0061] E. The thickness of the microcapsule repair layer is 25-55 μm.

[0062] A second aspect of this application provides a method for preparing the ultra-high temperature thermal barrier coating for a silicon carbide substrate, comprising:

[0063] A gradient transition layer and an adhesive layer are respectively formed on the surface of the silicon carbide substrate by laser cladding;

[0064] A dynamic stress control layer is obtained by depositing Ni, Ti, and Hf targets on the surface of the adhesive layer using physical vapor deposition.

[0065] A slurry containing microcapsule repair agent was applied to the surface of the dynamic stress control layer by ultrasonic atomization spraying to obtain the coated slurry.

[0066] A protective layer is formed on the surface of the coated slurry by pulsed plasma spraying to obtain an ultra-high temperature thermal barrier coating for silicon carbide substrate.

[0067] Optionally, the method for preparing the ultra-high temperature thermal barrier coating for the silicon carbide substrate satisfies at least one of the following conditions:

[0068] A. The power of the laser cladding is 2kW-3kW, the scanning speed is 5-10mm / s, the spraying distance is 100-120mm, the temperature is 1800-2000℃, and the powder feeding rate is 5-10g / min;

[0069] B. In the physical vapor deposition, the power of the Ni target is 120-150W, the power of the Ti target is 80-100W, and the power of the Hf target is 40-50W;

[0070] C. In the physical vapor deposition, the working gas includes argon, the flow rate of which is 20-30 sccm, the deposition pressure is 0.3-0.5 Pa, the pulse bias voltage is 80-150 V, and the deposition rate is 1.0-1.5 μm / h;

[0071] D. After the physical vapor deposition is performed, annealing is also performed at a temperature of 400-450°C for 1-3 hours.

[0072] E. The powder feeding rate of the pulsed plasma spraying is 2-4 g / min, the main arc power is 40-80 kW, the pulse frequency is 80-120 Hz, and the temperature of the silicon carbide substrate is 800-1000℃.

[0073] F. The protective layer comprises a first protective layer, a second protective layer, and a third protective layer stacked sequentially. The spraying distance for preparing the first protective layer is 100-120mm, and the spraying distance for preparing the third protective layer is 80-100mm.

[0074] A third aspect of this application provides a silicon carbide composite substrate, comprising a silicon carbide substrate and an ultra-high temperature thermal environment barrier coating for the silicon carbide substrate disposed on the surface of the silicon carbide substrate.

[0075] The coefficient of thermal expansion of the silicon carbide substrate is 4.0-4.5×10⁻⁶. -6 / K.

[0076] Compared with the prior art, the beneficial effects of this application include:

[0077] The ultra-high temperature thermal environment barrier coating for silicon carbide substrate provided in this application constructs a cross-scale coupling mechanism of "gradient stress buffering - dynamic phase transformation regulation - nanograin boundary strengthening" through a three-layer interface differentiation design: the gradient transition layer buffers the thermal expansion difference between the substrate and the coating, the adhesive layer connects the upper and lower layers and provides elastic buffering, the dynamic stress regulation layer absorbs high temperature strain through phase transformation, the protective layer resists ultra-high temperature and corrosion, and the microcapsule repair agent autonomously fills cracks; the five layers work together to form a "buffering-regulation-protection-repair" system, solving the problems of interface mismatch and insufficient protection.

[0078] The method for preparing ultra-high temperature thermal barrier coatings for silicon carbide substrates provided in this application includes laser cladding to control the gradient of the transition layer and the structure of the adhesive layer, physical vapor deposition to determine the dynamic layer composition, ultrasonic atomization of microcapsules, and pulsed plasma spraying of the protective layer. The preparation method has tightly connected steps, easy-to-control parameters, and can stably produce high-performance coatings, making it suitable for large-scale production.

[0079] The silicon carbide composite substrate provided in this application combines the lightweight and high specific strength of silicon carbide substrates with the ultra-high temperature protection capability of coatings. It has stable interface bonding, is resistant to thermal cycling failure, can extend the life of hot-end components, and is suitable for the extreme working conditions of aerospace. Attached Figure Description

[0080] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation on the scope of this application.

[0081] Figure 1 This is a schematic diagram of the structure of the ultra-high temperature thermal environment barrier coating for silicon carbide substrate provided in Example 1.

[0082] Figure 2 This is a diagram showing the thermal cycling life test process of the ultra-high temperature thermal environment barrier coating for silicon carbide substrate prepared in Example 1;

[0083] Figure 3 This is a diagram showing the oxidation lifetime test process of the ultra-high temperature thermal environment barrier coating for silicon carbide substrate prepared in Example 1.

[0084] Figure 4 This is a diagram showing the coating adhesion strength test process of the ultra-high temperature thermal barrier coating for silicon carbide substrate prepared in Example 1.

[0085] Explanation of key component symbols:

[0086] 100 - Silicon carbide substrate; 210 - Gradient transition layer; 220 - Adhesive layer; 230 - Dynamic stress control layer; 240 - Protective layer. Detailed Implementation

[0087] As used in this article:

[0088] "Prepared from" is synonymous with "comprising". The terms "comprising", "including", "having", "containing", or any other variations thereof as used herein are intended to cover non-exclusive inclusion. For example, a composition, step, method, article, or apparatus that includes the listed elements is not necessarily limited to those elements, but may include other elements not expressly listed or elements inherent to such composition, step, method, article, or apparatus.

[0089] When a quantity, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pair of any upper or preferred value with any lower or preferred value, regardless of whether the range is disclosed individually. For example, when the range “1–5” is disclosed, the described range should be interpreted as including ranges “1–4”, “1–3”, “1–2”, “1–2 and 4–5”, “1–3 and 5”, etc. When numerical ranges are described herein, unless otherwise stated, the range is intended to include its endpoints and all integers and fractions within that range.

[0090] In these embodiments, unless otherwise specified, the portions and percentages are all by weight.

[0091] "Parts by mass" refers to the basic unit of measurement that expresses the mass ratio of multiple components. One part can represent any unit mass, such as 1g or 2.689g. If we say that component A has "a" parts by mass and component B has "b" parts by mass, it means the ratio of the mass of component A to the mass of component B is a:b. Alternatively, it can mean that the mass of component A is aK and the mass of component B is bK (where K is any number representing a multiplier). It is important to understand that, unlike parts by mass, the sum of the mass parts of all components is not limited to 100 parts.

[0092] "And / or" is used to indicate that one or both of the described situations may occur, for example, A and / or B includes (A and B) and (A or B).

[0093] The first aspect of this application provides an ultra-high temperature thermal environment barrier coating for silicon carbide substrates, comprising a gradient transition layer, an adhesive layer, a dynamic stress control layer and a protective layer stacked sequentially.

[0094] The gradient transition layer includes Al2O3 and TiC. The Al2O3 content in the gradient transition layer decreases from the side closer to the silicon carbide substrate to the side closer to the adhesive layer, and the TiC content increases from the side closer to the silicon carbide substrate to the side closer to the adhesive layer.

[0095] It is important to note the thermal mismatch between traditional coatings and SiC substrates (Δα>5×10). -6 / K) leads to low-temperature debonding, while the gradient change in the thermal expansion coefficient of the gradient transition layer provided in this application is ≤2×10 -6 / ℃, achieving the transformation from SiC substrate (4.2×10⁻⁶) to 0.5℃. -6 / K) to the adhesive layer (8.5×10 -6 Δα ≤ 4.3 × 10⁻⁶ ( / K) -6 / K, compared to a traditional single transition layer (Δα>8×10) -6 / K) Reduces thermal mismatch stress by 50%;

[0096] The adhesive layer comprises an Al-Co-Cr-Fe-Ni-Ti-Si-B alloy;

[0097] The dynamic stress regulation layer comprises a Ni-Ti-Hf alloy;

[0098] It is important to note that the phase transformation temperature (1400-1600℃) of the Ni-Ti-Hf alloy in the dynamic stress control layer covers the coating's working temperature range. Below 1400℃, it is the parent phase (high stiffness), and above 1400℃, it undergoes a martensitic phase transformation (low stiffness + ≥6% strain tolerance). When the temperature rises above 1400℃, the dynamic stress control layer absorbs the thermal expansion difference between the bonding layer and the protective layer through the martensitic phase transformation. The measured strain tolerance ≥6% can offset 80% of the thermal strain of the coating system. At the same time, the microcapsule repair layer ruptures when the crack extends to 20μm and completes SiO2 filling within 10 minutes (repair rate ≥92%), preventing further stress concentration and solving the problem of temperature-zone interface delamination in traditional coatings.

[0099] The protective layer comprises Gd-Yb-Sm-Dy-Lu-Zr2O7 and SiC;

[0100] The coefficients of thermal expansion of the gradient transition layer, the adhesive layer, the dynamic stress control layer, and the protective layer increase from the direction closest to the silicon carbide substrate to the direction furthest from the silicon carbide substrate;

[0101] A microcapsule repair layer is further disposed between the dynamic stress regulation layer and the protective layer. The microcapsule repair layer includes a microcapsule repair agent. The microcapsule repair agent includes a SiC core and glassy SiO2 disposed on the surface of the SiC core.

[0102] It should be noted that the outer shell of the microcapsule repair agent is glassy SiO2 (melting point 1500℃). When the high-temperature crack propagates, it breaks, and SiC oxidizes to generate SiO2 (melting point 1713℃) to fill the crack.

[0103] In some embodiments, the gradient transition layer includes a first transition layer, a second transition layer, and a third transition layer stacked sequentially, wherein the first transition layer is located near the silicon carbide substrate, and the third transition layer is located near the adhesive layer, satisfying at least one of the following conditions:

[0104] A. The coefficient of thermal expansion of the first transition layer is 5.0-5.5×10⁻⁶. -6 / K;

[0105] Optionally, the coefficient of thermal expansion of the first transition layer can be 5.0 × 10⁻⁶. -6 / K, 5.1×10 -6 / K, 5.2×10 -6 / K, 5.3×10 -6 / K, 5.4×10 -6 / K, 5.5×10 -6 / K or 5.0-5.5×10 -6 Any value between / K;

[0106] B. The coefficient of thermal expansion of the second transition layer is 6.0-7.0 × 10⁻⁶. -6 / K;

[0107] Optionally, the coefficient of thermal expansion of the second transition layer can be 6.0 × 10⁻⁶. -6 / K, 6.5×10 -6 / K, 7.0×10 -6 / K or 6.0-7.0×10 -6 Any value between / K;

[0108] C. The coefficient of thermal expansion of the third transition layer is 7.5-8.5×10⁻⁶. -6 / K;

[0109] Optionally, the coefficient of thermal expansion of the third transition layer can be 7.5 × 10⁻⁶. -6 / K, 8.0×10 -6 / K, 8.5×10 -6 / K or 7.5-8.5×10 -6 Any value between / K;

[0110] It is important to note that the coefficient of thermal expansion of the gradient transition layer is not uniformly designed, but rather exhibits a continuous gradient change. The core purpose is to achieve "stress buffering gradient" through compositional gradients. Specifically, the coefficient of thermal expansion on the silicon carbide substrate side is approximately 5.0 × 10⁻⁶. -6 / K (represents the TiC-rich region, where the thermal expansion coefficient of the TiC-dominant phase is 7.2 × 10⁻⁶). -6 / K, after nanocrystal refinement and interface effect correction, is close to 4.2×10⁻⁶ of SiC substrate. -6 / K); Adhesive layer side: Coefficient of thermal expansion approximately 8.5 × 10⁻⁶ -6 / K (represents the Al2O3-rich region, with the Al2O3-dominant phase having a thermal expansion coefficient of 7.5 × 10⁻⁶). -6 / K);

[0111] In some embodiments, the coefficient of thermal expansion of the gradient transition layer is ≤2×10⁻⁶ in the thickness direction from the gradient transition layer to the adhesive layer. -6 The rate of increase is 3.5 × 10⁻⁶ / ℃·μm (total gradient difference 3.5 × 10⁻⁶). -6 / K, with a thickness of 50μm, the gradient change rate = 3.5 / 50 = 0.07×10 -6 ( / ℃·μm), ensuring that the change in the coefficient of thermal expansion within a 10μm thickness is ≤0.2×10. -6 / K, to achieve cross-scale coordination of "gradual stress relief from nanoscale components to micrometer scale";

[0112] The thermal expansion coefficient of the gradient transition layer is not uniform, but is achieved through compositional gradient control, ranging from 5.0 × 10⁻⁶. -6 / K to 8.5×10 -6 The gradient changes continuously, and the rate of change of gradient is strictly controlled to be ≤2×10. -6 / ℃·μm; By controlling the distribution of crystal phases at the nanoscale and gradually changing the composition along the thickness direction at the micrometer level, the originally irreconcilable huge thermal mismatch is transformed into a tolerable step-by-step stress buffer, which is a method to overcome the interface failure of ultra-high temperature coatings.

[0113] D. The mass percentage of Al2O3 in the first transition layer is 70-80%, and the mass percentage of TiC is 20-30%.

[0114] Optionally, the mass percentage of Al2O3 in the first transition layer can be any value between 70%, 75%, 80%, or 70-80%, and the mass percentage of TiC can be any value between 20%, 25%, 30%, or 20-30%.

[0115] E. The mass percentage of Al2O3 in the second transition layer is 50-60%, and the mass percentage of TiC is 40-50%.

[0116] Optionally, the mass percentage of Al2O3 in the second transition layer can be any value between 50%, 55%, 60%, or 50-60%, and the mass percentage of TiC can be any value between 40%, 45%, 50%, or 40-50%.

[0117] F. The mass percentage of Al2O3 in the third transition layer is 30-40%, and the mass percentage of TiC is 60-70%.

[0118] Optionally, the mass percentage of Al2O3 in the third transition layer can be any value between 30%, 35%, 40%, or 30-40%, and the mass percentage of TiC can be any value between 60%, 65%, 70%, or 60-70%.

[0119] It should be noted that the first, second, and third transition layers achieve their thermal expansion coefficients by adjusting the ratio of Al2O3 to TiC, from 4.2 × 10⁻⁶ to that of the substrate. -6 The smooth transition of / K to the initial value of the underlying adhesive layer, with the specific gradient distribution as follows:

[0120] 1. Near the silicon carbide substrate (first transition layer): mainly composed of Al2O3. Utilizing the interfacial compatibility between Al2O3 and silicon carbide, and by reducing the proportion of high-expansion phases, the coefficient of thermal expansion in this region is controlled at 5.0-5.5 × 10⁻⁶. -6 / K, with substrate (4.2×10 -6 The difference between / K) was reduced to ≤1.3×10 -6 / K, initially buffers the stress between the substrate and the transition layer;

[0121] 2. Intermediate region of the transition layer (second transition layer): The proportion of Al2O3 gradually decreases, the proportion of TiC gradually increases, and the coefficient of thermal expansion increases linearly with the composition to 6.0-7.0×10⁻⁶. -6 / K, to achieve the "intermediate transition" of the gradient;

[0122] 3. Near the bottom adhesive layer (third transition layer): mainly composed of TiC, utilizing the wettability advantage of TiC with high-entropy alloys to increase the coefficient of thermal expansion to 7.5-8.5×10. -6 / K, and the initial value of the underlying adhesive layer (optimized value 8-9×10). -6 / K) difference ≤ 0.5×10 -6 / K, to complete the matching with the underlying adhesive layer;

[0123] G. The thickness of the gradient transition layer is 30-50 μm;

[0124] Optionally, the thickness of the gradient transition layer can be 30 μm, 40 μm, 50 μm or any value between 30 and 50 μm;

[0125] H. The difference in the coefficient of thermal expansion between adjacent layers of the gradient transition layer, the adhesive layer, the dynamic stress control layer, and the protective layer is independently ≤0.5×10⁻⁶. -6 / K.

[0126] Optionally, the difference in the coefficient of thermal expansion between adjacent layers of the gradient transition layer, adhesive layer, dynamic stress control layer, and protective layer can each be independently set to 0.1 × 10⁻⁶. -6 / K, 0.2×10 -6 / K, 0.3×10 -6 / K, 0.4×10 -6 / K, 0.5×10 -6 / K or ≤0.5×10 -6 Any value for / K.

[0127] In some embodiments, the ultra-high temperature thermal barrier coating for the silicon carbide substrate satisfies at least one of the following conditions:

[0128] A. The Si and B contents in the adhesive layer gradually decrease along the direction from the side closer to the gradient transition layer to the side closer to the dynamic stress control layer, and the Cr and Fe contents in the adhesive layer gradually increase along the direction from the side closer to the gradient transition layer to the side closer to the dynamic stress control layer.

[0129] B. The surface thermal expansion coefficient of the adhesive layer on the side closest to the gradient transition layer is 7.8-8.3×10⁻⁶. -6 / K, the surface thermal expansion coefficient of the adhesive layer on the side closest to the dynamic stress control layer is 8.5×10. -6 / K;

[0130] Optionally, the surface thermal expansion coefficient of the adhesive layer on the side closest to the gradient transition layer can be 7.8 × 10⁻⁶. -6 / K, 7.9×10 -6 / K、8×10 -6 / K, 8.1×10 -6 / K, 8.2×10 -6 / K, 8.3×10 -6 / K or 7.8-8.3×10 -6 Any value between / K;

[0131] C. The rate of change of the coefficient of thermal expansion per micrometer of the adhesive layer is ≤0.01×10⁻⁶. -6 / K;

[0132] Optionally, the rate of change of the coefficient of thermal expansion per micrometer of thickness in the adhesive layer can be 0.0001 × 10⁻⁶. -6 / K, 0.001×10 -6 / K, 0.01×10 -6 / K or ≤0.01×10 -6 Any value between / K;

[0133] D. The adhesive layer includes a honeycomb structure;

[0134] It should be noted that the honeycomb structure can achieve elastic deformation of the pores, buffer thermal stress, and strengthen the interfacial shear strength with the micro-hard phase (TiC) in the gradient transition layer, thus suppressing interfacial delamination during low-temperature (<800℃) cycling.

[0135] E. The porosity of the adhesive layer is 10-15%;

[0136] Optionally, the porosity of the adhesive layer can be any value between 10%, 13%, 15%, or 10-15%.

[0137] It should be noted that when the porosity of the adhesive layer is less than 10%, the elastic deformation capacity is insufficient, and when the porosity is greater than 15%, the structural strength of the coating decreases. Therefore, when the porosity of the adhesive layer is 10-15%, it is the optimal range that balances single-row deformation buffer stress and structural strength.

[0138] F. The thickness of the adhesive layer is 0.5-1.0 mm.

[0139] Optionally, the thickness of the adhesive layer can be any value between 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm, 1mm or 0.5-1.0mm.

[0140] In some embodiments, the ultra-high temperature thermal barrier coating for the silicon carbide substrate satisfies at least one of the following conditions:

[0141] A. The thickness of the dynamic stress regulation layer is 50-100 μm;

[0142] Optionally, the thickness of the dynamic stress regulation layer can be any value between 50μm, 60μm, 70μm, 80μm, 90μm, 100μm or 50-100μm;

[0143] B. The Ni-Ti-Hf alloy, based on a total mass of 100%, comprises:

[0144] Ni 48-52%, Ti 33-37%, Hf 13-17%;

[0145] Optionally, in the Ni-Ti-Hf alloy, based on a total mass of 100%, Ni can be any value between 48%, 49%, 50%, 51%, 52% or 48-52%, Ti can be any value between 33%, 34%, 35%, 36%, 37% or 33-37%, and Hf can be any value between 13%, 14%, 15%, 16%, 17% or 13-17%.

[0146] It is important to note that when the Ni mass content is below 48%, the stability of austenite decreases, and martensite prematurely precipitates below 1400℃, leading to a sharp drop in stiffness in the mid-temperature range (1000-1400℃) (modulus drops from 80GPa to 60GPa), and interfacial stress control fails. When the Ni mass content is above 52%, the phase transformation temperature range shifts upward (Ms>1650℃), exceeding the maximum service temperature of the coating, making it impossible to achieve a complete martensitic phase transformation at 1600℃ (phase transformation rate <80%). When the Hf mass content is >17%, harmful HfO2 particles (size >50nm) will form, reducing the strain recovery rate and increasing production costs.

[0147] In some embodiments, Ti and Hf have the following synergistic effect: when the mass content of Ti is less than 33% or more than 37%, the phase transition temperature range shifts by ±15°C for every ±1% of the mass content of Ti, which needs to be coupled with the mass content of Hf. For every +1% of the mass content of Hf, the Ms point increases by 5°C to ensure the target phase transition range of 1400-1600°C.

[0148] C. The phase transition temperature of the dynamic stress regulation layer is 1400-1600℃;

[0149] Optionally, the phase transition temperature of the dynamic stress control layer can be any value between 1400℃, 1500℃, 1600℃ or 1400-1600℃.

[0150] D. The strain tolerance of the dynamic stress control layer is ≥6%;

[0151] Optionally, the strain tolerance of the dynamic stress control layer can be any value of 6%, 10%, 20% or ≥6%;

[0152] E. The interfacial bonding strength of the dynamic stress control layer is ≥45MPa;

[0153] Optionally, the interfacial bonding strength of the dynamic stress control layer can be any value between 45 MPa, 50 MPa, 60 MPa or ≥45 MPa.

[0154] F. The coefficient of thermal expansion of the dynamic stress-regulating layer is 8-9 × 10⁻⁶. -6 / K.

[0155] Optionally, the coefficient of thermal expansion of the dynamic stress-regulating layer can be 8×10⁻⁶. -6 / K, 8.5×10 -6 / K、9×10 -6 / K or 8-9×10 -6 Any value between / K.

[0156] In some embodiments, the ultra-high temperature thermal barrier coating for the silicon carbide substrate satisfies at least one of the following conditions:

[0157] A. The particle size of SiC in the protective layer is 50-100 nm;

[0158] Optionally, the particle size of SiC in the protective layer can be any value between 50nm, 60nm, 70nm, 80nm, 90nm, 100nm or 50-100nm.

[0159] B. The thickness of the protective layer is 0.8-1.5 mm;

[0160] Optionally, the thickness of the protective layer can be 0.8mm, 1mm, 1.2mm, 1.5mm or any value between 0.8mm and 1.5mm;

[0161] C. The thermal conductivity of the protective layer is ≤0.7 W / m•K;

[0162] Optionally, the thermal conductivity of the protective layer can be 0.1 W / m•K, 0.2 W / m•K, 0.4 W / m•K, 0.5 W / m•K, 0.7 W / m•K or any value ≤0.7 W / m•K;

[0163] D. The density of the protective layer is ≥98%, and the surface roughness is ≤1μm;

[0164] Optionally, the density of the protective layer can be any value between 98%, 99%, 99.9% or ≥98%, and the surface roughness can be any value between 0.1μm, 0.5μm, 1μm or ≤1μm.

[0165] E. The surface thermal expansion coefficient of the protective layer on the side closest to the dynamic stress control layer is 8.5 × 10⁻⁶. -6 / K, the surface thermal expansion coefficient of the protective layer on the side away from the dynamic stress control layer is 8.8-9.0×10. -6 / K;

[0166] Optionally, the surface thermal expansion coefficient of the adhesive layer on the side furthest from the dynamic stress control layer can be 8.8 × 10⁻⁶. -6 / K, 8.9×10 -6 / K, 9.0×10 -6 / K or 8.8-9.0×10 -6 Any value between / K;

[0167] F. The protective layer includes a first protective layer, a second protective layer, and a third protective layer stacked sequentially, wherein the first protective layer is the side closer to the dynamic stress control layer, and the third protective layer is the side farther away from the dynamic stress control layer;

[0168] The first protective layer includes Gd 0.2 Yb 0.2 Sm 0.2 Dy 0.2 Lu 0.2 Zr₂O₇ and SiC;

[0169] The second protective layer includes GdYbSmDyLuZr2O7 and SiC, wherein the mass content of Lu, Yb, Sm and Dy decreases in a gradient from the first protective layer to the third protective layer, and the mass content of Gd increases in a gradient from the first protective layer to the third protective layer.

[0170] The third protective layer comprises SiC and Gd2Zr2O7.

[0171] It is worth noting that this application breaks through the performance bottleneck of traditional single rare earth zirconate coatings, achieving ultra-high temperature protection capability of 1600℃ through a composite mechanism of "high-entropy lattice distortion + nanoparticle toughening + interface thermal resistance regulation". Nano-SiC particles are uniformly dispersed in the Gd-Yb-Sm-Dy-Lu-Zr2O7 matrix (HE-REZ) of the protective layer, forming a "granular nail + grain boundary bridging" strengthening effect: SiC particles (size <100nm) hinder dislocation slip, effectively improving the coating hardness; SiC particles at grain boundaries bridge crack tips, increasing fracture toughness and suppressing sudden brittle fracture at high temperatures; the intrinsic thermal conductivity of Gd-Yb-Sm-Dy-Lu-Zr2O7 (at 1600℃) is approximately 1.2W / m•K, which is reduced to ≤0.7W / m•K through the interfacial phonon scattering effect after the introduction of nano-SiC; SiC nanoparticles... The atomic-scale interface between the particles and the matrix Gd-Yb-Sm-Dy-Lu-Zr2O7 scatters phonons with a mean free path of 5-10 nm, causing a decrease in lattice thermal conductivity. The high thermal conductivity of SiC particles (490 W / m•K) becomes ineffective at the nanoscale, instead forming "thermal conductivity islands" that block continuous heat conduction paths (traditional micron-sized SiC particles increase thermal conductivity). Furthermore, SiC slowly oxidizes at 1600℃ to form the SiO2 glass phase, filling micro-defects on the coating surface and forming a double barrier of "HE-REZ oxide film + SiO2 sealing layer". Rare earth elements such as Gd / Yb in HE-REZ generate high-melting-point oxides (Gd2O3 melting point is 2420℃), inhibiting oxygen diffusion into the coating. The SiO2 glass phase (melting point is 1713℃) preferentially reacts during CMAS etching above 1350℃, generating an inert Gd-Si-O-Ca phase, preventing molten salt penetration.

[0172] It is also important to note that the first protective layer strictly adheres to the "five-element equimolar" design, meaning that the molar percentage of each of the five rare earth elements—Gd, Yb, Sm, Dy, and Lu—in zirconate (RE2Zr2O7) is 20%. This ratio is optimized through thermodynamic calculations to ensure that the five elements form a stable high-entropy solid solution with a stable coefficient of thermal expansion of 8.5 × 10⁻⁶. -6 / K; The second protective layer adjusts the rare earth element ratio according to the principle of "gradually reducing the mass content of low-expansion elements and directionally dominating high-expansion elements". The specific rules are as follows: low-expansion components (Lu, Yb) are preferentially reduced: Lu (corresponding to Lu2Zr2O7, thermal expansion coefficient 7.8-8.3×10 -6 / K) and Yb (corresponding to Yb2Zr2O7, 8.0-8.5×10 -6 / K) as a low-expansion contributing element, its molar proportion decreases linearly from 20%, decreasing by 2-3% for every 0.1 mm increase in thickness, until it reaches 0% in the top layer region; the medium-expansion component (Dy) provides a coordinated transition: Dy (corresponding to Dy2Zr2O7, 8.3-8.8×10 -6 / K) is used as an intermediate regulating element, its proportion gradually decreasing from 20%, with a deceleration rate of 1 / 2 that of Lu / Yb (in some embodiments, it decreases by 1-1.5% per 0.1 mm), ensuring that the coefficient of thermal expansion does not change abruptly when the low-expansion element is phased out; the high-expansion component (Sm) transitions rapidly, and Gd increases directionally: Sm (corresponding to Sm2Zr2O7, 8.8-9.2×10 -6 Gd (corresponding to Gd₂Zr₂O₇, 8.5-9.0×10⁻⁶) is a highly expanding element, with a decreasing rate consistent with Lu / Yb; meanwhile, in some embodiments, Gd (corresponding to Gd₂Zr₂O₇, 8.5-9.0×10⁻⁶) is used. -6 The molar percentage of rare earth elements (Gd) increases linearly from 20%, and the percentage increases by 4-5% for every 0.1 mm increase in thickness, filling the gap left by the withdrawal of other elements. As the rare earth elements decrease, the top layer of Gd becomes a stable cubic phase (phase transition temperature > 2000℃), avoiding the volume expansion cracking caused by phase transformation (such as cubic → monoclinic) in traditional coatings.

[0173] In some embodiments, the ultra-high temperature thermal barrier coating for the silicon carbide substrate satisfies at least one of the following conditions:

[0174] A. In the second protective layer, the mass contents of Lu, Yb, and Sm decrease independently from 20% of the total metal content to 0% along the direction from the first protective layer to the third protective layer;

[0175] B. In the second protective layer, the decrease rate of Dy is 0.5 times the decrease rate of Lu;

[0176] C. In the second protective layer, the mass content of Gd increases gradually from 20% to 100% of the total metal content along the direction from the first protective layer to the third protective layer;

[0177] D. The thickness of the first protective layer is 0.2-0.4 mm;

[0178] Optionally, the thickness of the first protective layer can be 0.2mm, 0.3mm, 0.4mm, or any value between 0.2mm and 0.4mm;

[0179] E. The thickness of the second protective layer is 0.3-0.7 mm;

[0180] Optionally, the thickness of the second protective layer can be any value between 0.3mm, 0.4mm, 0.5mm, 0.6mm, 0.7mm, or 0.3-0.7mm;

[0181] F. The thickness of the third protective layer is 0.2-0.4 mm;

[0182] Optionally, the thickness of the third protective layer can be any value between 0.2 mm, 0.3 mm, 0.4 mm, or 0.2-0.4 mm; G. The third protective layer comprises a columnar crystal structure.

[0183] It is important to note that the intergranular gaps in the columnar crystal structure are 5-10 nm, forming a "microcrack trapping network" with the nanocrystalline region (the region where the grain size is at the nanoscale). The permeability of CMAS molten salt (mainly composed of CaO-MgO-Al2O3-SiO2) at 1350℃ is ≤2μm / 240h (compared to ≥20μm / 240h for traditional coatings). This is because the vertical gaps between the columnar crystals hinder the lateral penetration of the molten salt, while the highly active sites at the nanograin boundaries promote the formation of a dense Gd2SiO5 barrier layer in the molten salt.

[0184] Dynamic stress modulation of the SMA layer reduces grain boundary opening displacement (≤5nm) and cuts off the molten salt penetration path;

[0185] H. The mass content of SiC in the first protective layer, the second protective layer, and the third protective layer is independently 10-20%.

[0186] Optionally, the mass content of SiC in the first protective layer, the second protective layer, and the third protective layer can be independently 10%, 15%, 20%, or any value between 10% and 20%.

[0187] It should be noted that when the mass content of SiC is <15%, the spacing between nanoparticles is >200nm, which makes it impossible to form an effective interfacial scattering network, resulting in a decrease in thermal conductivity; when the mass content of SiC is >15%, the distance between particles is <50nm, which causes agglomeration, resulting in a decrease in coating density and a reduction in interfacial bonding strength.

[0188] In some embodiments, the ultra-high temperature thermal barrier coating for the silicon carbide substrate satisfies at least one of the following conditions:

[0189] A. The particle size of the microcapsule repair agent is 20-50 μm;

[0190] Optionally, the particle size of the microcapsule repair agent can be any value between 20μm, 30μm, 40μm, 50μm or 20-50μm;

[0191] In some embodiments, the initial size of typical coating cracks caused by thermal mismatch or CMAS (calcium magnesium aluminum silicate) erosion is 10-20 μm. When the particle size of the microcapsule repair agent is 20-50 μm, it can ensure that the microcapsules are penetrated when the crack extends to 20 μm (rupture probability >90%), releasing the SiC repair agent. If the particle size of the microcapsule repair agent is <20 μm, it may be bypassed by small cracks, resulting in a decrease in repair efficiency. Furthermore, the shell of the microcapsule repair agent is glassy SiO2. If the particle size of the microcapsule repair agent is <20 μm, the shell strength is insufficient, and it may break prematurely during spraying. If the particle size of the microcapsule repair agent is >50 μm, the microcapsule spacing is too large, and the crack may extend in the gap without triggering rupture. In addition, the shell of the microcapsule repair agent is glassy SiO2. If the particle size is too large (>50 μm), it will introduce interface defects, increase porosity, and reduce the bonding strength between the dynamic stress control layer and the protective layer.

[0192] B. The density of the microcapsule repair agent is 5-10 capsules / mm². 2 ;

[0193] Optionally, the density of the microcapsule repair agent can be 5 capsules / mm². 2 6 pieces / mm 2 7 pieces / mm 2 8 pieces / mm 2 9 pieces / mm 2 10 pieces / mm 2 Or 5-10 per mm 2 Any value between;

[0194] It should be noted that when the density of the microcapsule repair agent is <5 capsules / mm², 2 At that time, the repair agent per unit area was insufficient; when the density of the microcapsule repair agent was >10 capsules / mm² 2 When this happens, it leads to uneven stiffness at the local interface, causing new stress concentration points;

[0195] It should also be noted that the rupture mechanism of microcapsule repair agents is as follows:

[0196] 1. Mechanical stress-driven fracture: When the crack extends to the location of the microcapsule repair agent (spacing 50-100μm), the stress concentration at the tip causes the glass shell to fracture brittlely;

[0197] 2. Temperature-assisted effect: When the temperature is greater than 1400℃, the glass shell softens and the fracture stress drops to 50MPa. Even small cracks (10μm) can trigger fracture, thus improving the repair efficiency in high-temperature areas.

[0198] In some embodiments, the SiC oxidation onset temperature in air is 1300°C, and the reaction rate constant k = 5 × 10⁻⁶ at 1600°C. -5At a speed of m / s, it takes approximately 40 seconds for 20μm SiC particles to be completely oxidized. The resulting SiO2 expands 1.8 times in volume, just enough to fill the crack. The generated SiO2 is an amorphous glassy phase (melting point as high as 1713℃) and exhibits fluidity at 1600℃ (viscosity of 10). 6 Pa•s), which can penetrate to 5nm-level microcracks and form a dense repair layer (density ≥95%), which is 25% higher than that of traditional ceramic particle fillers (density 70%);

[0199] C. The purity of the SiC core is ≥99%;

[0200] Optionally, the purity of the SiC core can be any value of 99%, 99.9%, 99.99%, or ≥99%;

[0201] It is important to note that the SiC purity of the microcapsule core should be ≥99% to avoid abnormal oxidation caused by impurities (such as Fe) (generating FeSiO3, a low-melting-point phase with a melting point of 1170℃), and to ensure that the repair product is pure SiO2.

[0202] D. The thickness of the glassy SiO2 is 1-5 μm;

[0203] Optionally, the thickness of the glassy SiO2 can be 1μm, 2μm, 3μm, 4μm, 5μm or any value between 1 and 5μm;

[0204] E. The thickness of the microcapsule repair layer is 25-55 μm.

[0205] Optionally, the thickness of the microcapsule repair layer can be any value between 25μm, 30μm, 35μm, 40μm, 45μm, 50μm, 55μm or 25-55μm.

[0206] It is important to note that in the low-temperature region (<1000℃): the honeycomb structure (porous elastic deformation) of the bonding layer + gradient transition layer (achieving a gradient transition of the thermal expansion coefficient between the substrate and the coating) dominates, controlling the interfacial stress below 20MPa (traditional coatings >50MPa) to avoid debonding; in the medium-temperature region (1000-1400℃): the dynamic stress control layer bears shear stress in a high-rigidity state of the parent phase, and when the microcapsule repair layer is not activated, stress is dissipated through grain boundary slip in the interfacial nanocrystallization region, maintaining a bonding strength of ≥35MPa; in the high-temperature region (1400-1650℃): the martensitic phase transformation of the dynamic stress control layer absorbs thermal strain, the microcapsules rupture and repair cracks, and at the same time, the rare earth gradient diffusion of the protective layer forms a surface Gd2O3 protective film (melting point 2420℃), extending the oxidation resistance life by 4 times compared to the traditional YSZ coating (≥100h at 1600℃).

[0207] The ultra-high temperature thermal environment barrier coating for silicon carbide substrate provided in this application has a thermal cycle life (1000℃) of ≥2000 cycles and a CMAS corrosion penetration rate of ≤2μm / 240h. Through the cross-scale design of multi-layer interfaces (from micron-level honeycomb structure to nano-grain boundaries), this application overcomes the defects of multi-layer coatings in the prior art, forming an intelligent interface system of "stress sensing-dynamic response-self-healing", and finally achieving "zero debonding, low failure and long life" performance under long-term service at 1650℃.

[0208] It is also worth noting that this application solves the problem of "low-temperature debonding and high-temperature failure" of traditional coatings through a combination of material system and structural design. Specifically, in the material system, a five-equal molar ratio rare earth zirconate of Gd-Yb-Sm-Dy-Lu is used for the first time. Through the synergistic effect of multiple components, the gradient matching of the coefficient of thermal expansion with the silicon carbide substrate is achieved, breaking through the temperature resistance bottleneck of traditional single rare earth coatings. For the first time, a Ni-Ti-Hf alloy with dynamic stress regulation layer is introduced into the ultra-high temperature coating interface. Through thermally induced martensitic phase transformation, thermal stress is absorbed (strain tolerance ≥6%), which improves the interfacial bonding strength compared with traditional gradient structure and forms a dual self-healing mechanism with microcapsule repair agent. In terms of structure, a double-layer gradient full-temperature range protection is adopted. The gradient transition layer and the protective layer form a gradient composite system spanning a temperature range of 450℃, with a gradient change in the coefficient of thermal expansion ≤2×10. -6 / ℃, solving the problem of "low temperature debonding and high temperature failure" of traditional coatings.

[0209] A second aspect of this application provides a method for preparing the ultra-high temperature thermal barrier coating for a silicon carbide substrate, comprising:

[0210] A gradient transition layer and an adhesive layer are respectively formed on the surface of the silicon carbide substrate by laser cladding;

[0211] A dynamic stress control layer is obtained by depositing Ni, Ti, and Hf targets on the surface of the adhesive layer using physical vapor deposition.

[0212] A slurry containing microcapsule repair agent was applied to the surface of the dynamic stress control layer by ultrasonic atomization spraying to obtain the coated slurry.

[0213] It is important to note that during the ultrasonic atomization spraying process, the surface temperature of the microcapsule repair agent should be controlled to ≤1000℃ (achieved through cooling airflow) to prevent the glass shell from softening.

[0214] A protective layer is formed on the surface of the coated slurry by pulsed plasma spraying to obtain an ultra-high temperature thermal barrier coating for silicon carbide substrate.

[0215] In some embodiments, the method for preparing the ultra-high temperature thermal barrier coating for the silicon carbide substrate satisfies at least one of the following conditions:

[0216] A. The power of the laser cladding is 2kW-3kW, the scanning speed is 5-10mm / s, the spraying distance is 100-120mm, the temperature is 1800-2000℃, and the powder feeding rate is 5-10g / min;

[0217] Optionally, the power of laser cladding can be any value between 2kW, 2.5kW, 3kW or 2kW-3kW; the scanning speed can be any value between 5 mm / s, 7 mm / s, 10 mm / s or 5-10 mm / s; the spraying distance can be any value between 100mm, 110mm, 120mm or 100-120mm; the temperature can be any value between 1800℃, 1900℃, 2000℃ or 1800-2000℃; and the powder feeding rate can be any value between 5g / min, 7g / min, 10g / min or 5-10g / min.

[0218] It is important to note that when preparing the porous structure of the bonding layer using laser cladding, the melting state of the raw material powder is controlled: fully molten particles (60-70 wt%) form a dense substrate, semi-molten particles (20-30 wt%) retain their morphology to form a porous framework, and unmolten particles (≤10 wt%) do not require additional heat treatment and can be dissolved by the residual heat of the laser and subsequent physical vapor deposition annealing (400-450℃ / 1-3h). Furthermore, the porosity is positively correlated with the scanning speed, and the temperature of the molten pool is monitored using an infrared thermal imager (accuracy ±5℃) to ensure uniform pore distribution.

[0219] B. In the physical vapor deposition, the power of the Ni target is 120-150W, the power of the Ti target is 80-100W, and the power of the Hf target is 40-50W;

[0220] Optionally, in physical vapor deposition, the power of the Ni target can be any value between 120W, 130W, 140W, 150W or 120-150W, the power of the Ti target can be any value between 80W, 90W, 100W or 80-100W, and the power of the Hf target can be any value between 40W, 45W, 50W or 40-50W.

[0221] C. In the physical vapor deposition, the working gas includes argon, the flow rate of which is 20-30 sccm, 20-30 sccm is 0.3-0.5 Pa, the pulse bias voltage is 80-150 V, and the deposition rate is 1.0-1.5 μm / h;

[0222] Optionally, in physical vapor deposition, the argon flow rate can be any value between 20 sccm, 25 sccm, 30 sccm, or 20-30 sccm; the 20-30 sccm can be any value between 0.3 Pa, 0.4 Pa, 0.5 Pa, or 0.3-0.5 Pa; the pulse bias voltage can be any value between 80 V, 100 V, 120 V, 150 V, or 80-150 V; and the deposition rate can be any value between 1.0 μm / h, 1.1 μm / h, 1.2 μm / h, 1.3 μm / h, 1.4 μm / h, 1.5 μm / h, or 1.0-1.5 μm / h.

[0223] D. After the physical vapor deposition is performed, annealing is also performed at a temperature of 400-450°C for 1-3 hours.

[0224] Optionally, the annealing temperature can be any value between 400℃, 410℃, 420℃, 430℃, 440℃, 450℃ or 400-450℃, and the time can be any value between 1h, 2h, 3h or 1-3h.

[0225] E. The powder feeding rate of the pulsed plasma spraying is 2-4 g / min, the main arc power is 40-80 kW, the pulse frequency is 80-120 Hz, and the temperature of the silicon carbide substrate is 800-1000℃.

[0226] Optionally, the powder feeding rate of pulsed plasma spraying can be any value between 2g / min, 3g / min, 4g / min or 2-4g / min, the main arc power can be any value between 40kW, 60kW, 80kW or 40-80kW, the pulse frequency can be any value between 80Hz, 100Hz, 120Hz or 80-120Hz, and the temperature of the silicon carbide substrate can be any value between 800℃, 900℃, 1000℃ or 800-1000℃.

[0227] It is important to note that, to match the gradual change in composition, the core parameters of pulsed plasma spraying are synergistically adjusted along the thickness direction to ensure consistent melting and deposition behavior of zirconate powders with different rare earth elements: Main arc power and pulse frequency: Main arc power is kept constant at 40-80kW and pulse frequency at 80-120Hz from the bottom layer to the top layer to ensure stable plasma flame energy and avoid compositional segregation caused by energy fluctuations; Spraying distance is 80-100mm to shorten the distance and enhance powder melting; The substrate temperature is maintained at 800-1000℃ through infrared heating to ensure uniform diffusion of different rare earth zirconates.

[0228] F. The protective layer comprises a first protective layer, a second protective layer, and a third protective layer stacked sequentially. The spraying distance for preparing the first protective layer is 100-120mm, and the spraying distance for preparing the third protective layer is 80-100mm.

[0229] Optionally, the spraying distance for preparing the first protective layer can be any value between 100mm, 110mm, 120mm or 100-120mm, and the spraying distance for preparing the third protective layer can be any value between 80mm, 90mm, 100mm or 80-100mm.

[0230] A third aspect of this application provides a silicon carbide composite substrate, comprising a silicon carbide substrate and an ultra-high temperature thermal environment barrier coating for the silicon carbide substrate disposed on the surface of the silicon carbide substrate.

[0231] The coefficient of thermal expansion of the silicon carbide substrate is 4.0-4.5 × 10⁻⁶. -6 / K.

[0232] Optionally, the coefficient of thermal expansion of the silicon carbide substrate can be 4.0 × 10⁻⁶. -6 / K, 4.1×10 -6 / K, 4.2×10 -6 / K, 4.3×10 -6 / K, 4.4×10 -6 / K, 4.5×10 -6 / K or 4-4.5×10 -6 Any value between / K.

[0233] The implementation schemes of this application will be described in detail below with reference to specific embodiments. However, those skilled in the art will understand that the following embodiments are only for illustrating this application and should not be regarded as limiting the scope of this application. Unless otherwise specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments used without specified manufacturers are all conventional products that can be purchased commercially.

[0234] Example 1

[0235] This embodiment 1 provides an ultra-high temperature thermal barrier coating for silicon carbide substrates, the structure of which is shown in the figure. Figure 1 As shown, the layer includes a gradient transition layer 210, an adhesive layer 220, a dynamic stress regulation layer 230, and a protective layer 240 sequentially stacked on the surface of a silicon carbide substrate 100. The coefficients of thermal expansion of the gradient transition layer, adhesive layer, dynamic stress regulation layer, and protective layer increase from the direction closest to the silicon carbide substrate to the direction furthest from the silicon carbide substrate. The microcapsule repair layer includes a microcapsule repair agent, which includes a SiC core and glassy SiO2 disposed on the surface of the SiC core.

[0236] The gradient transition layer comprises Al2O3 and TiC. The Al2O3 content in the gradient transition layer decreases gradually from the side closest to the silicon carbide substrate to the side closest to the adhesive layer, while the TiC content increases gradually from the side closest to the silicon carbide substrate to the side closest to the adhesive layer. The gradient transition layer comprises a first transition layer, a second transition layer, and a third transition layer stacked sequentially. The first transition layer is located closer to the silicon carbide substrate, and the third transition layer is located closer to the adhesive layer. The coefficient of thermal expansion of the first transition layer is 5.2 × 10⁻⁶. -6 / K, the coefficient of thermal expansion of the second transition layer is 6.5×10 -6 / K, the coefficient of thermal expansion of the third transition layer is 8.0×10. -6 / K, the mass percentage of Al2O3 in the first transition layer is 75%, and the mass percentage of TiC is 25%; the mass percentage of Al2O3 in the second transition layer is 55%, and the mass percentage of TiC is 45%; the mass percentage of Al2O3 in the third transition layer is 35%, and the mass percentage of TiC is 65%; the total thickness of the gradient transition layer is 45μm, and the thickness ratio of the first transition layer, the second transition layer and the third transition layer is 1:1:1;

[0237] The binder layer comprises an Al-Co-Cr-Fe-Ni-Ti-Si-B alloy. The Si and B contents in the binder layer gradually decrease from the side closest to the gradient transition layer to the side closest to the dynamic stress control layer, while the Cr and Fe contents gradually increase from the side closest to the gradient transition layer to the side closest to the dynamic stress control layer. The surface thermal expansion coefficient near the gradient transition layer is 8.0 × 10⁻⁶. -6 / K, the surface thermal expansion coefficient on the side closest to the dynamic stress control layer is 8.5×10. -6 / K, the rate of change of the coefficient of thermal expansion per micrometer of thickness in the adhesive layer (8.5-8.0) / 800 = 0.000625×10 -6 / K; The adhesive layer has a honeycomb structure with a porosity of 12% and a thickness of 0.8mm;

[0238] The dynamic stress control layer comprises a Ni-Ti-Hf alloy, wherein Ni accounts for 50% by mass, Ti accounts for 35% by mass, and Hf accounts for 15% by mass. The dynamic stress control layer has a thickness of 80 μm, a phase transformation temperature of 1500℃, a strain tolerance of 6.5%, an interfacial bonding strength of 50 MPa, and a coefficient of thermal expansion of 8.5 × 10⁻⁶. -6 / K;

[0239] The microcapsule repair agent has a particle size of 35 μm and a density of 8 particles / mm². 2The purity of the SiC core is 99.5%, the thickness of the glassy SiO2 is 3μm, and the thickness of the microcapsule repair layer is 40μm.

[0240] The protective layer comprises Gd-Yb-Sm-Dy-Lu-Zr2O7 and SiC. The SiC has a particle size of 80 nm, a mass content of 15%, a thickness of 1.2 mm, a thermal conductivity of 0.6 W / m•K, a density of 98.5%, and a surface roughness of 0.8 μm. The protective layer consists of a first protective layer, a second protective layer, and a third protective layer stacked sequentially. The first protective layer is located closer to the dynamic stress control layer, and the third protective layer is located further away from the dynamic stress control layer. The first protective layer (25% of the total thickness of the protective layer) includes Gd... 0.2 Yb 0.2 Sm 0.2 Dy 0.2 Lu 0.2 The second protective layer (50% of the total thickness of the protective layer) consists of Zr₂O₇ and SiC, wherein the mass content of Lu, Yb, Sm, and Dy decreases gradually from the first to the third protective layer, with Lu, Yb, and Sm decreasing from 20% to 0% of the total metal content, and the decrease rate of Dy being 0.5 times that of Lu; the mass content of Gd increases gradually from the first to the third protective layer, with the mass content increasing gradually from 20% to 100% of the total metal content; the third protective layer (25% of the total thickness of the protective layer, columnar crystal structure) consists of SiC and Gd₂Zr₂O₇.

[0241] The difference in the coefficient of thermal expansion between adjacent layers in the gradient transition layer, adhesive layer, dynamic stress control layer, and protective layer is ≤0.5×10⁻⁶. -6 / K.

[0242] The second aspect of this embodiment provides a method for preparing an ultra-high temperature thermal barrier coating for a silicon carbide substrate, the specific steps of which are as follows:

[0243] S1: Substrate pretreatment: The surface of the silicon carbide substrate is sandblasted (80 mesh), ultrasonically cleaned (ethanol + deionized water), dried, and preheated to 300℃ to prevent the substrate from cracking during cladding.

[0244] S2: Laser cladding is used, with process parameters of laser power 2.5kW, scanning speed 8mm / s, spraying distance 110mm, melt pool temperature 1900℃, and powder feeding rate 8g / min; the gradient transition layer and the adhesive layer are clad onto the surface of the silicon carbide substrate.

[0245] S3: A dynamic stress control layer is obtained by depositing Ni, Ti, and Hf targets on the surface of the binder layer using physical vapor deposition. The working gas includes argon, with a flow rate of 25 sccm, a deposition pressure of 0.4 Pa, a pulse bias of 120 V, and a deposition rate of 1.2 μm / h.

[0246] S4: After physical vapor deposition, annealing is performed at a temperature of 420℃ for 2 hours.

[0247] S5: After annealing, an ultrasonic atomization spray is used to apply a slurry containing microcapsule repair agent to the surface of the dynamic stress control layer. The atomization pressure is 0.3 MPa, the nozzle distance is 50 mm, the surface temperature is controlled at 800℃, and a single spray thickness of 40 μm is applied to ensure uniform distribution of the repair agent (density 8 capsules / mm²). 2 The coated slurry is obtained;

[0248] S6: A PS-PVD device equipped with 5 independent powder delivery channels (corresponding to Gd2Zr2O7, Yb2Zr2O7, Sm2Zr2O7, Dy2Zr2O7, and Lu2Zr2O7 nanoparticles with a particle size of 50-100nm) is used. The powder delivery rate of each channel is adjusted in real-time by a programmable logic controller (PLC) (range: 0.5-5g / min). A first, second, and third protective layer are sequentially deposited on the surface of the coated slurry using pulsed plasma spraying. During the preparation of the first protective layer, the powder delivery rate of all 5 channels is the same (2.5g / min), and the spraying distance is... The spraying distance is 110mm to ensure the same equimolar ratio of the five components. When preparing the second protective layer, the powder feeding rate of the Lu, Yb, Dy, and Sm channels is dynamically reduced according to a gradual change rule, while the powder feeding rate of the Gd channel is simultaneously increased to ensure a linear change in the component ratio. When preparing the third protective layer, the Lu, Yb, Sm, and Dy channels are closed, and only the Gd channel is kept in place for powder feeding (rate 3.5g / min), with a spraying distance of 90mm, to achieve deposition of a single Gd system. When setting the first, second, and third protective layers, the main arc power is 60kW, the pulse frequency is 100Hz, and the temperature of the silicon carbide substrate is 900℃.

[0249] The third aspect of this embodiment provides a silicon carbide composite substrate, which is prepared by the above-described preparation method.

[0250] Example 2

[0251] The difference from Example 1 is that the coefficient of thermal expansion of the first transition layer is 5.0 × 10⁻⁶. -6 / K, the coefficient of thermal expansion of the second transition layer is 6.0×10 -6 / K, the coefficient of thermal expansion of the third transition layer is 8.0×10. -6 / K, the mass percentage of Al2O3 in the first transition layer is 70%, and the mass percentage of TiC is 30%; the mass percentage of Al2O3 in the second transition layer is 50%, and the mass percentage of TiC is 50%; the mass percentage of Al2O3 in the third transition layer is 30%, and the mass percentage of TiC is 70%.

[0252] Example 3

[0253] The difference from Example 1 is that the dynamic stress control layer is different. The dynamic stress control layer comprises a Ni-Ti-Hf alloy, wherein Ni accounts for 48% by mass, Ti accounts for 37% by mass, and Hf accounts for 15% by mass. The thickness of the dynamic stress control layer is 50 μm, the phase transformation temperature is 1455 °C, the strain tolerance is 6.0%, the interfacial bonding strength is 45 MPa, and the coefficient of thermal expansion is 8.5 × 10⁻⁶. -6 / K.

[0254] Comparative Example 1

[0255] The difference from Example 1 is that no gradient transition layer is set.

[0256] Comparative Example 2

[0257] The difference from Example 1 is that no adhesive layer is provided.

[0258] Comparative Example 3

[0259] The difference from Example 1 is that no dynamic stress control layer is provided.

[0260] Comparative Example 4

[0261] The difference from Example 1 is that no microcapsule repair layer is provided.

[0262] Comparative Example 5

[0263] The difference from Example 1 is that no protective layer is provided.

[0264] Comparative Example 6

[0265] The difference from Example 1 is that the positions of the gradient transition layer and the dynamic stress control layer are replaced.

[0266] The silicon carbide substrates prepared in the above embodiments and comparative examples were subjected to performance tests using ultra-high temperature thermal environment barrier coatings. The test results are shown in Table 1.

[0267] The thermal cycling life test process for the ultra-high temperature thermal barrier coating on the silicon carbide substrate prepared in Example 1 is as follows: Figure 2 As shown, the antioxidant lifespan test is as follows: Figure 3 As shown, the coating adhesion strength test process is as follows: Figure 4 As shown.

[0268] Table 1 Performance Tests

[0269]

[0270] analyze:

[0271] The results above show that the coatings in Examples 1-3 all meet the requirements for ultra-high temperature service and exhibit overall stable performance. Example 1, due to the optimal balance of parameters in the gradient transition layer (Al2O3 75% / TiC 25%) and the dynamic stress control layer (Ni 50% / Ti 35% / Hf 15%), achieves the best thermal cycle life (2200 cycles) at 1000℃, oxidation resistance life (120h) at 1600℃, CMAS penetration rate (1.5μm / 240h) at 1350℃, and coating adhesion strength (50MPa). Examples 2 (with Al2O3 in the transition layer reduced to 70%) and 3 (with Ni in the dynamic layer reduced to 48%) only show slight performance decreases due to minor adjustments in local parameters (e.g., 1000℃ cycle life ≥ 2050 cycles, CMAS penetration rate ≤ 1.8μm / 240h), validating the parameter ranges mentioned above. The scientific validity of the comparative examples is evident in the following: Comparative Example 1 (without a gradient transition layer) had a large thermal mismatch between the substrate and the adhesive layer, resulting in a cycle life of only 50 cycles at 1000℃; Comparative Example 2 (without an adhesive layer) had a bonding strength of only 20MPa due to the failure of the ceramic-metal interface; Comparative Example 3 (without a dynamic layer) had a short oxidation resistance life of only 70h at 1600℃ due to insufficient high-temperature strain absorption; Comparative Example 4 (without a microcapsule layer) had a CMAS permeability of 15μm / 240h due to the inability to repair cracks; Comparative Example 5 (without a protective layer) failed directly at 1600℃ due to the lack of an ultra-high temperature barrier; and Comparative Example 6 (with layer misalignment) had a bonding strength of only 8MPa due to the melting of the dynamic layer at high temperatures. All of these examples demonstrate that the functional layers, such as the gradient transition layer, adhesive layer, and dynamic layer, as well as the layer sequence of "substrate → transition layer → adhesive layer → dynamic layer," are indispensable, further highlighting the rationality and superiority of the "full-layer synergy + parameter balance" design in Example 1.

[0272] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

[0273] Furthermore, those skilled in the art will understand that although some embodiments herein include certain features included in other embodiments but not others, combinations of features from different embodiments are intended to be within the scope of this application and form different embodiments. For example, in the foregoing claims, any of the claimed embodiments can be used in any combination. The information disclosed in this background section is intended only to enhance the understanding of the general background of this application and should not be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

Claims

1. A high-temperature thermal barrier coating for silicon carbide substrates, characterized in that, It includes a gradient transition layer, an adhesive layer, a dynamic stress control layer, and a protective layer that are stacked sequentially. The gradient transition layer includes Al2O3 and TiC. The Al2O3 content in the gradient transition layer decreases from the side closer to the silicon carbide substrate to the side closer to the adhesive layer, and the TiC content increases from the side closer to the silicon carbide substrate to the side closer to the adhesive layer. The adhesive layer comprises an Al-Co-Cr-Fe-Ni-Ti-Si-B alloy; The dynamic stress regulation layer comprises a Ni-Ti-Hf alloy; The protective layer comprises Gd-Yb-Sm-Dy-Lu-Zr2O7 and SiC; The coefficients of thermal expansion of the gradient transition layer, the adhesive layer, the dynamic stress control layer, and the protective layer increase from the direction closest to the silicon carbide substrate to the direction furthest from the silicon carbide substrate; A microcapsule repair layer is further disposed between the dynamic stress regulation layer and the protective layer. The microcapsule repair layer includes a microcapsule repair agent. The microcapsule repair agent includes a SiC core and glassy SiO2 disposed on the surface of the SiC core.

2. The ultra-high temperature thermal barrier coating for silicon carbide substrates according to claim 1, characterized in that, The gradient transition layer includes a first transition layer, a second transition layer, and a third transition layer stacked sequentially. The first transition layer is located near the silicon carbide substrate, and the third transition layer is located near the adhesive layer. At least one of the following conditions is satisfied: A. The coefficient of thermal expansion of the first transition layer is 5.0-5.5×10⁻⁶. -6 / K; B. The coefficient of thermal expansion of the second transition layer is 6.0-7.0 × 10⁻⁶. -6 / K; C. The coefficient of thermal expansion of the third transition layer is 7.5-8.5×10⁻⁶. -6 / K; D. The mass percentage of Al2O3 in the first transition layer is 70-80%, and the mass percentage of TiC is 20-30%. E. The mass percentage of Al2O3 in the second transition layer is 50-60%, and the mass percentage of TiC is 40-50%. F. The mass percentage of Al2O3 in the third transition layer is 30-40%, and the mass percentage of TiC is 60-70%. G. The thickness of the gradient transition layer is 30-50 μm; H. The difference in the coefficient of thermal expansion between adjacent layers of the gradient transition layer, the adhesive layer, the dynamic stress control layer, and the protective layer is independently ≤0.5×10⁻⁶. -6 / K.

3. The ultra-high temperature thermal barrier coating for silicon carbide substrates according to claim 1, characterized in that, At least one of the following conditions must be met: A. The Si and B contents in the adhesive layer gradually decrease along the direction from the side closer to the gradient transition layer to the side closer to the dynamic stress control layer, and the Cr and Fe contents in the adhesive layer gradually increase along the direction from the side closer to the gradient transition layer to the side closer to the dynamic stress control layer. B. The surface thermal expansion coefficient of the adhesive layer on the side closest to the gradient transition layer is 7.8-8.3×10⁻⁶. -6 / K, the surface thermal expansion coefficient of the adhesive layer on the side closest to the dynamic stress control layer is 8.5×10. -6 / K; C. The rate of change of the coefficient of thermal expansion per micrometer of the adhesive layer is ≤0.01×10⁻⁶. -6 / K; D. The adhesive layer includes a honeycomb structure; E. The porosity of the adhesive layer is 10-15%; F. The thickness of the adhesive layer is 0.5-1.0 mm.

4. The ultra-high temperature thermal barrier coating for silicon carbide substrates according to claim 1, characterized in that, At least one of the following conditions must be met: A. The thickness of the dynamic stress regulation layer is 50-100 μm; B. The Ni-Ti-Hf alloy, based on a total mass of 100%, comprises: Ni 48-52%, Ti 33-37%, Hf 13-17%; C. The phase transition temperature of the dynamic stress regulation layer is 1400-1600℃; D. The strain tolerance of the dynamic stress control layer is ≥6%; E. The interfacial bonding strength of the dynamic stress control layer is ≥45MPa; F. The coefficient of thermal expansion of the dynamic stress-regulating layer is 8-9 × 10⁻⁶. -6 / K.

5. The ultra-high temperature thermal barrier coating for silicon carbide substrates according to claim 1, characterized in that, At least one of the following conditions must be met: A. The particle size of SiC in the protective layer is 50-100 nm; B. The thickness of the protective layer is 0.8-1.5 mm; C. The thermal conductivity of the protective layer is ≤0.7 W / m•K; D. The density of the protective layer is ≥98%, and the surface roughness is ≤1μm; E. The surface thermal expansion coefficient of the protective layer on the side closest to the dynamic stress control layer is 8.5 × 10⁻⁶. -6 / K, the surface thermal expansion coefficient of the protective layer on the side away from the dynamic stress control layer is 8.8-9.0×10. -6 / K; F. The protective layer includes a first protective layer, a second protective layer, and a third protective layer stacked sequentially, wherein the first protective layer is the side closer to the dynamic stress control layer, and the third protective layer is the side farther away from the dynamic stress control layer; The first protective layer includes Gd 0.2 Yb 0.2 Sm 0.2 Dy 0.2 Lu 0.2 Zr₂O₇ and SiC; The second protective layer includes GdYbSmDyLuZr2O7 and SiC, wherein the mass content of Lu, Yb, Sm and Dy decreases in a gradient from the first protective layer to the third protective layer, and the mass content of Gd increases in a gradient from the first protective layer to the third protective layer. The third protective layer comprises SiC and Gd2Zr2O7.

6. The ultra-high temperature thermal barrier coating for silicon carbide substrates according to claim 5, characterized in that, At least one of the following conditions must be met: A. In the second protective layer, the mass contents of Lu, Yb, and Sm decrease independently from 20% of the total metal content to 0% along the direction from the first protective layer to the third protective layer; B. In the second protective layer, the decrease rate of Dy is 0.5 times the decrease rate of Lu; C. In the second protective layer, the mass content of Gd increases gradually from 20% to 100% of the total metal content along the direction from the first protective layer to the third protective layer; D. The thickness of the first protective layer is 0.2-0.4 mm; E. The thickness of the second protective layer is 0.3-0.7 mm; F. The thickness of the third protective layer is 0.2-0.4 mm; G. The third protective layer comprises a columnar crystal structure; H. The mass content of SiC in the first protective layer, the second protective layer, and the third protective layer is independently 10-20%.

7. The ultra-high temperature thermal barrier coating for silicon carbide substrates according to claim 1, characterized in that, At least one of the following conditions must be met: A. The particle size of the microcapsule repair agent is 20-50 μm; B. The density of the microcapsule repair agent is 5-10 capsules / mm². 2 ; C. The purity of the SiC core is ≥99%; D. The thickness of the glassy SiO2 is 1-5 μm; E. The thickness of the microcapsule repair layer is 25-55 μm.

8. A method for preparing an ultra-high temperature thermal barrier coating for a silicon carbide substrate according to any one of claims 1-7, characterized in that, include: A gradient transition layer and an adhesive layer are respectively formed on the surface of the silicon carbide substrate by laser cladding; A dynamic stress control layer is obtained by depositing Ni, Ti, and Hf targets on the surface of the adhesive layer using physical vapor deposition. A slurry containing microcapsule repair agent was applied to the surface of the dynamic stress control layer by ultrasonic atomization spraying to obtain the coated slurry. A protective layer is formed on the surface of the coated slurry by pulsed plasma spraying to obtain an ultra-high temperature thermal barrier coating for silicon carbide substrate.

9. The method for preparing an ultra-high temperature thermal barrier coating for a silicon carbide substrate according to claim 8, characterized in that, At least one of the following conditions must be met: A. The power of the laser cladding is 2kW-3kW, the scanning speed is 5-10mm / s, the spraying distance is 100-120mm, the temperature is 1800-2000℃, and the powder feeding rate is 5-10g / min; B. In the physical vapor deposition, the power of the Ni target is 120-150W, the power of the Ti target is 80-100W, and the power of the Hf target is 40-50W; C. In the physical vapor deposition, the working gas includes argon, the flow rate of which is 20-30 sccm, the deposition pressure is 0.3-0.5 Pa, the pulse bias voltage is 80-150 V, and the deposition rate is 1.0-1.5 μm / h; D. After the physical vapor deposition is performed, annealing is also performed at a temperature of 400-450°C for 1-3 hours. E. The powder feeding rate of the pulsed plasma spraying is 2-4 g / min, the main arc power is 40-80 kW, the pulse frequency is 80-120 Hz, and the temperature of the silicon carbide substrate is 800-1000℃. F. The protective layer comprises a first protective layer, a second protective layer, and a third protective layer stacked sequentially. The spraying distance for preparing the first protective layer is 100-120mm, and the spraying distance for preparing the third protective layer is 80-100mm.

10. A silicon carbide composite substrate, characterized in that, The invention includes a silicon carbide substrate and an ultra-high temperature thermal environment barrier coating for a silicon carbide substrate as described in any one of claims 1-7, disposed on the surface of the silicon carbide substrate. The coefficient of thermal expansion of the silicon carbide substrate is 4.0-4.5×10⁻⁶. -6 / K.

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