A method for preparing a thermal barrier coating

Abstract

The present invention relates to the technical field of thermal barrier coatings, and particularly to a method for preparing a thermal barrier coating. An embodiment of the present invention provides a method for preparing a thermal barrier coating, including: spraying a slurry on a substrate to be protected by an ion spraying process to obtain a thermal insulation layer with longitudinal cracks; wherein, the longitudinal cracks are perpendicular to the thermal insulation layer, one end of the longitudinal crack extends to the surface of the thermal insulation layer, and the other end is located inside the thermal insulation layer, the slurry includes a thermal barrier material, and the thermal barrier material contains an oxide of at least one of strontium, zirconium, neodymium, samarium, europium, gadolinium, dysprosium, erbium, ytterbium, lutetium or yttrium; filling an endothermic material into the longitudinal cracks by a vacuum impregnation process. The embodiment of the present invention provides a method for preparing a thermal barrier coating, which has excellent heat insulation and thermal shock stability.

Description

Technical Field

[0001] The present invention relates to the technical field of thermal barrier coatings, and particularly relates to a preparation method of a thermal barrier coating. Background Art

[0002] As a commonly used coating for engines and turbine blades in the aerospace field, the thermal barrier coating has excellent heat insulation performance. However, in the face of sudden temperature increases such as combustion in the combustion chamber, thermal shock will occur, resulting in a shortened coating life.

[0003] Therefore, in view of the above deficiencies, a thermal shock coating with excellent thermal shock stability is needed. Summary of the Invention

[0004] An embodiment of the present invention provides a preparation method of a thermal barrier coating, which has excellent heat insulation and thermal shock stability.

[0005] An embodiment of the present invention provides a preparation method of a thermal barrier coating, including:

[0006] Spray the slurry on the substrate to be protected by an ion spraying process to obtain a heat insulation layer with longitudinal cracks; wherein, the longitudinal cracks are perpendicular to the heat insulation layer, one end of the longitudinal crack extends to the surface of the heat insulation layer, and the other end is located inside the heat insulation layer. The slurry includes a thermal barrier material, and the thermal barrier material contains oxides of at least one of strontium, zirconium, neodymium, samarium, europium, gadolinium, dysprosium, erbium, ytterbium, lutetium or yttrium;

[0007] Fill the longitudinal cracks with an endothermic material by a vacuum impregnation process.

[0008] In a possible design, before filling the longitudinal cracks with the endothermic material by the vacuum impregnation process, it further includes:

[0009] Process kaolin by high-temperature treatment, acid treatment and ultrasonic dispersion treatment in sequence to obtain nanoscale kaolin;

[0010] Mix the nanoscale kaolin and a liquid to obtain an endothermic material;

[0011] The step of filling the longitudinal cracks with the endothermic material by the vacuum impregnation process includes:

[0012] Place the heat insulation layer in a vacuum negative pressure environment;

[0013] Cover the entire upper part of the heat insulation layer with the endothermic material;

[0014] Apply a positive pressure to the endothermic material and perform ultrasonic dispersion treatment;

[0015] Make the endothermic material fill the longitudinal cracks.

[0016] In a possible design, the liquid includes water;

[0017] After filling the longitudinal cracks with the heat-absorbing material, it further includes:

[0018] Precisely evaporate the water in part of the longitudinal cracks by controlling the temperature, humidity, and heating duration.

[0019] In a possible design, the liquid includes a salt solution; wherein, the salt solution includes a phosphate solution, a chloride solution, and a fluoride solution;

[0020] After filling the longitudinal cracks with the heat-absorbing material, it further includes:

[0021] Prepare a salt solution with a concentration lower than the preset concentration;

[0022] Precisely evaporate the water in the salt solution in part of the longitudinal cracks by controlling the temperature, humidity, and heating duration to make the concentration of the salt solution reach the preset concentration.

[0023] In a possible design, the volume of the longitudinal cracks accounts for 20 - 30% of the volume of the thermal insulation layer.

[0024] In a possible design, the depth length of the longitudinal cracks is not less than 65 - 90% of the thickness of the thermal insulation layer.

[0025] In a possible design, the heat-absorbing material includes at least one of fatty acid solid-liquid phase change materials and alcohol solid-liquid phase change materials;

[0026] Filling the heat-absorbing material into the longitudinal cracks by using a vacuum impregnation process includes:

[0027] Heat the solid-liquid phase change material in a vacuum environment to make it in a liquid phase;

[0028] Soak the thermal insulation layer with the liquid-phase solid-liquid phase change material and apply a positive pressure to the liquid-phase solid-liquid phase change material to make the liquid-phase solid-liquid phase change material penetrate into the longitudinal cracks;

[0029] After the longitudinal cracks are filled, cool down and reduce the pressure, then take it out.

[0030] In a possible design, spraying the slurry on the substrate to be protected by using an ion spraying process to obtain a thermal insulation layer with longitudinal cracks includes:

[0031] Spray the slurry including a plurality of vacuum balls on the substrate to be protected by using an ion spraying process to obtain a thermal insulation layer with longitudinal cracks and vacuum balls.

[0032] In a possible design, the preparation material of the shell of the vacuum ball includes silicon dioxide and / or alumina, and the outer diameter of the vacuum ball is 5-10 μm.

[0033] In a possible design, after filling the longitudinal cracks with the heat-absorbing material by using the vacuum impregnation process, the following steps are further included:

[0034] A sealing layer is prepared on the side of the heat insulation layer away from the protective substrate by means of plasma spraying; wherein, the preparation material of the sealing layer includes the thermal barrier material, and the sealing layer is used to seal the opening of the longitudinal crack on the surface of the heat insulation layer;

[0035] The thickness of the heat insulation layer is 50-500 μm, and the thickness of the sealing layer is 5-20 μm.

[0036] The present invention has at least the following beneficial effects compared with the prior art:

[0037] By controlling the slurry composition and process parameters of the plasma spraying process, longitudinal cracks can be obtained. The longitudinal cracks can improve the mechanical properties of the coating and also improve the heat insulation effect. In order to improve its thermal shock stability, a heat-absorbing material is filled in the longitudinal cracks. In order to enable the heat-absorbing material to smoothly penetrate into the longitudinal cracks, the vacuum impregnation process is used to fill the longitudinal cracks with the heat-absorbing material. The heat-absorbing material has excellent heat-absorbing performance and a large latent heat. When the thermal barrier coating is subjected to an instantaneous high-temperature impact, the heat-absorbing material can absorb a large amount of heat, forming a buffering effect on the heat impact, thereby achieving the effect of improving the thermal stability of the thermal barrier coating. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0039] Figure 1 is a flowchart of a method for preparing a thermal barrier coating provided by an embodiment of the present invention;

[0040] Figure 2 is a schematic structural diagram of a thermal barrier coating provided by an embodiment of the present invention.

[0041] In the figure:

[0042] 1 - heat insulation layer;

[0043] 11 - longitudinal crack;

[0044] 12 - heat-absorbing material;

[0045] 13 - Vacuum sphere;

[0046] 2 - Sealing layer;

[0047] 100 - Substrate. Detailed implementation manners

[0048] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0049] In the description of the embodiments of the present invention, unless otherwise clearly specified and limited, the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance; unless otherwise specified or stated, the term "plurality" means two or more; the terms "connection", "fixation", etc. shall be understood in a broad sense. For example, "connection" can be a fixed connection, a detachable connection, an integral connection, or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0050] In the description of this specification, it should be understood that the orientation terms such as "upper" and "lower" described in the embodiments of the present invention are described from the angles shown in the accompanying drawings and should not be construed as limiting the embodiments of the present invention. In addition, in the context, it should also be understood that when it is mentioned that an element is connected "above" or "below" another element, it can not only be directly connected "above" or "below" another element, but also be indirectly connected "above" or "below" another element through an intermediate element.

[0051] As mentioned above, the thermal barrier material can play an obvious heat insulation role at a thickness between dozens and hundreds of micrometers, and can protect the substrate to be protected by the thermal barrier coating from or be less affected by high temperatures. Although the thermal barrier coatings in the prior art can achieve good heat insulation effects, however, when the ambient temperature rises instantaneously, their thermal shock stability is poor, which may lead to a decrease in the service life of the coating. To solve the above problems, the present invention proposes a thermal barrier coating with a heat insulation layer having longitudinal cracks.

[0052] Please refer to Figure 1 and Figure 2 , the embodiments of the present invention provide a preparation method for a thermal barrier coating, including:

[0053] The slurry is sprayed on the substrate 100 to be protected by an ion spraying process to obtain a thermal insulation layer 1 with longitudinal cracks; wherein, the longitudinal cracks 11 are perpendicular to the thermal insulation layer 1, one end of the longitudinal crack extends to the surface of the thermal insulation layer 1, and the other end is located inside the thermal insulation layer 1. The slurry includes a thermal barrier material, and the thermal barrier material contains oxides of at least one of strontium, zirconium, neodymium, samarium, europium, gadolinium, dysprosium, erbium, ytterbium, lutetium or yttrium;

[0054] The endothermic material 12 is filled into the longitudinal cracks by a vacuum impregnation process.

[0055] By controlling the slurry composition and process parameters of the plasma spraying process, longitudinal cracks can be obtained. The longitudinal cracks can improve the mechanical properties of the coating and also improve the heat insulation effect. To improve its thermal shock stability, the endothermic material 12 is filled into the longitudinal cracks. In order to enable the endothermic material 12 to smoothly penetrate into the longitudinal cracks 11, the endothermic material 12 is filled into the longitudinal cracks 11 by a vacuum impregnation process. The endothermic material 12 has excellent endothermic performance and a large latent heat. When the thermal barrier coating is subjected to an instantaneous high-temperature impact, the endothermic material 12 can absorb a large amount of heat, forming a buffering effect on the heat impact, thereby achieving the effect of improving the thermal stability of the thermal barrier coating.

[0056] In some embodiments of the present invention, before filling the endothermic material 12 into the longitudinal cracks by a vacuum impregnation process, it further includes:

[0057] Kaolin is processed by high-temperature treatment, acid treatment and ultrasonic dispersion treatment in sequence to obtain nano-scale kaolin;

[0058] The nano-scale kaolin and a liquid are mixed to obtain the endothermic material 12;

[0059] Filling the endothermic material 12 into the longitudinal cracks by a vacuum impregnation process includes:

[0060] Placing the thermal insulation layer 1 in a vacuum negative pressure environment;

[0061] Covering the endothermic material 12 on the entire upper part of the thermal insulation layer 1;

[0062] Applying a positive pressure to the endothermic material 12 and performing ultrasonic dispersion treatment;

[0063] Enabling the endothermic material 12 to fill the longitudinal cracks 11.

[0064] In this embodiment, in order to fill the longitudinal crack 11 with the heat-absorbing material 12, all gases are first discharged under vacuum negative pressure to make the longitudinal crack 11 in a vacuum environment, which is convenient for the heat-absorbing material 12 to enter the longitudinal crack 11. Then, the heat-absorbing material 12 is heated to make the heat-absorbing material 12 cover the entire heat-insulating layer 1. The part of the heat-absorbing material 12 close to the longitudinal crack 11 enters the longitudinal crack 11. A positive pressure is comprehensively applied to the heat-absorbing material 12 covering the heat-insulating layer 1, and ultrasonic waves are applied to make the heat-absorbing material 12 fill the longitudinal crack 11.

[0065] In this embodiment, the heat-absorbing material 12 can be kaolin absorbed with liquid. The kaolin has a nano-sized particle size, and at the same time has the properties of water absorption and water retention, and also has heat-insulating properties. It can absorb and store the liquid with a large latent heat while ensuring the heat-insulating performance of the heat-insulating layer 1 for heat absorption buffering during high heat shock. Natural kaolin can be obtained with a nano-sized porous nanostructure through high-temperature treatment, acid treatment, and ultrasonic dispersion. Its nano-sized particle size can enter the micron-sized longitudinal crack 11 and absorb the high-latent heat liquid through capillary water absorption.

[0066] In some embodiments of the present invention, the liquid includes water;

[0067] After filling the longitudinal crack 11 with the heat-absorbing material 12, it further includes:

[0068] Precisely evaporate part of the water in the longitudinal crack 11 by controlling the temperature, humidity, and heating duration.

[0069] In this embodiment, the liquid can be water, and water has a high latent heat.

[0070] It should be noted that the space inside the longitudinal crack 11 is larger than the volume of the heat-absorbing material 12 itself. Such a setting makes the heat-absorbing material 12 not completely occupy the entire space of the longitudinal crack 11, leaving space for the expansion of the heat-absorbing material 12 during the endothermic phase change, preventing the longitudinal crack 11 from being widened after the heat-absorbing material 12 absorbs heat and undergoes a phase change expansion, and ultimately shortening the coating life.

[0071] After the heat-absorbing material 12 fills the longitudinal crack 11, the heat-absorbing material 12 often fills the crack completely. In order to make the heat-absorbing material 12 partially occupy the longitudinal crack 11, part of the liquid can be removed after the heat-absorbing material 12 fills the crack completely. Specifically, when the liquid is water, part of the water in the longitudinal crack 11 can be precisely evaporated by controlling the temperature, humidity, and heating duration.

[0072] In some embodiments of the present invention, the liquid includes a salt solution; wherein, the salt solution includes a phosphate solution, a chloride solution, and a fluoride solution;

[0073] After filling the longitudinal crack 11 with the heat-absorbing material 12, it further includes:

[0074] Prepare a salt solution with a concentration lower than the preset concentration;

[0075] Precisely evaporate part of the water in the salt solution in the longitudinal crack 11 by controlling the temperature, humidity, and heating duration, so that the concentration of the salt solution is the preset concentration.

[0076] Preferably, the liquid is a salt solution. Besides having a high latent heat, the salt solution also has the advantage of reducing the thermal conductivity. As described above, in order to prevent the salt solution from filling the longitudinal crack 11, when the liquid is a salt solution, a salt solution with a concentration lower than the preset concentration can be prepared first, and then the concentration can be increased and the volume can be reduced by precisely evaporating part of the water in the salt solution in the longitudinal crack 11 by controlling the temperature, humidity, and heating duration.

[0077] In some embodiments of the present invention, the volume of the longitudinal crack 11 accounts for 20 - 30% of the volume of the heat insulation layer 1.

[0078] In this embodiment, when the longitudinal crack 11 is within the above volume fraction range, the longitudinal crack 11 absorbs the heat-absorbing material 12, and the heat insulation layer 1 has good thermal shock stability and a long service life at the same time.

[0079] In some embodiments of the present invention, the depth length of the longitudinal crack 11 is not less than 65 - 90% of the thickness of the heat insulation layer 1.

[0080] In this embodiment, a larger depth length can accommodate more heat-absorbing material 12, which can greatly improve the thermal shock stability, but the longitudinal crack 11 cannot completely penetrate the heat insulation layer 1. If it completely penetrates, the service life of the heat insulation layer 1 will decrease.

[0081] In some embodiments of the present invention, the heat-absorbing material 12 includes at least one of fatty acid-based solid-liquid phase change materials and alcohol-based solid-liquid phase change materials;

[0082] Filling the heat-absorbing material 12 into the longitudinal crack by using a vacuum impregnation process, including:

[0083] Heating the solid-liquid phase change material in a vacuum environment to make it in a liquid phase;

[0084] Soaking the heat insulation layer 1 with the liquid-phase solid-liquid phase change material and applying a positive pressure to the liquid-phase solid-liquid phase change material to make the liquid-phase solid-liquid phase change material penetrate into the longitudinal crack 11;

[0085] After the longitudinal crack 11 is filled, after cooling and depressurizing, take it out.

[0086] In this embodiment, the heat-absorbing material 12 can be at least one of fatty acid solid-liquid phase change materials and alcohol solid-liquid phase change materials. Both fatty acid solid-liquid phase change materials and alcohol solid-liquid phase change materials have high latent heat and can absorb more heat during phase change. They have good miscibility, and their simultaneous application can further expand the temperature range for regulating phase change.

[0087] When filling the longitudinal crack 11 with the solid-liquid phase change material, in order to prevent the solid-liquid phase change material in the solid state from expanding due to heat absorption and phase change and enlarging the longitudinal crack 11, an expansion space needs to be reserved in the longitudinal crack 11, and the longitudinal crack 11 can be filled in a high-temperature vacuum environment. Specifically, the solid-liquid phase change material is heated in a vacuum environment to make it in a liquid phase. The vacuum environment prevents its oxidation. The heat-insulating layer 1 is soaked with the liquid-phase solid-liquid phase change material, and a positive pressure is applied to the liquid-phase solid-liquid phase change material to make the liquid-phase solid-liquid phase change material penetrate into the longitudinal crack 11. After the longitudinal crack 11 is filled, after cooling and depressurizing, the material is taken out. At this time, the solid-liquid phase change material shrinks into a solid state and is located inside the longitudinal crack 11, not completely filling the longitudinal crack 11, leaving an expansion space for heat absorption and phase change in the later use stage.

[0088] In some embodiments of the present invention, the slurry is sprayed on the substrate 100 to be protected by an ion spraying process to obtain a heat-insulating layer 1 with longitudinal cracks, including:

[0089] The slurry including a plurality of vacuum spheres 13 is sprayed on the substrate 100 to be protected by an ion spraying process to obtain a heat-insulating layer 1 with longitudinal cracks and vacuum spheres 13.

[0090] In this embodiment, in order to further increase the heat insulation performance of the thermal barrier coating, a plurality of vacuum spheres 13 are further provided in the heat-insulating layer 1. The inside of the vacuum sphere 13 is a vacuum environment, and vacuum cannot conduct heat, further increasing the heat insulation performance of the heat-insulating layer 1. In addition, under the same heat transfer path, the smaller the cross-sectional area of heat transfer, the slower the heat conduction speed. The path length of the external heat transferred to the substrate 100 layer is the thickness of the coating, but in the heat-insulating layer 1 provided with the vacuum spheres 13, due to the existence of the vacuum spheres 13, the cross-sectional area parallel to the surface of the substrate 100 is reduced, further increasing the heat insulation effect.

[0091] It should be noted that due to the small particle size of the vacuum sphere 13 and its circular shape, it has strong compressive strength and can increase the compressive strength of the heat-insulating layer 1 itself.

[0092] In some embodiments of the present invention, the preparation material of the shell of the vacuum sphere 13 includes silicon dioxide and / or aluminum oxide, and the outer diameter of the vacuum sphere 13 is 5-10 μm.

[0093] In this embodiment, the housing of the vacuum sphere 13 is made of a heat-insulating material, which can ensure its heat-insulating effect. At the same time, the material itself has relatively high strength. When the outer diameter of the vacuum sphere 13 is within the above range, both strength and heat-insulating effect can be taken into account.

[0094] In some embodiments of the present invention, after filling the heat-absorbing material 12 into the longitudinal cracks by using the vacuum impregnation process, it further includes:

[0095] A sealing layer 2 is prepared on the side of the heat-insulating layer 1 away from the protection substrate 100 by means of plasma spraying; wherein, the preparation material of the sealing layer 2 includes a thermal barrier material, and the sealing layer 2 is used to seal the opening of the longitudinal crack 11 on the surface of the heat-insulating layer 1;

[0096] The thickness of the heat-insulating layer 1 is 50 - 500 μm, and the thickness of the sealing layer 2 is 5 - 20 μm.

[0097] It can be understood that the area of the longitudinal crack 11 on the surface is extremely small. During its operation, the internal heat-absorbing material 12 hardly contacts the air, and the degree of oxidation is relatively small. However, in order to further increase its antioxidant property at high temperatures and extend its service life, a sealing layer 2 can be provided outside the heat-insulating layer 1 to isolate the internal and external environments of the longitudinal crack 11.

[0098] It should be noted that after obtaining the heat-insulating layer 1 filled with the heat-absorbing material 12, the sealing layer 2 can also be sprayed by using the ion spraying technology in an oxygen-free environment.

[0099] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a thermal barrier coating, characterized in that: include: The slurry is sprayed on the substrate to be protected by an ion spraying process to obtain a thermal insulation layer with longitudinal cracks; wherein the longitudinal cracks are perpendicular to the thermal insulation layer, one end of the longitudinal cracks extends to the surface of the thermal insulation layer, and the other end is located inside the thermal insulation layer, and the slurry includes a thermal barrier material, and the thermal barrier material includes an oxide of at least one of strontium, zirconium, neodymium, samarium, europium, gadolinium, dysprosium, erbium, ytterbium, lutetium or yttrium; Filling the heat absorbing material into the longitudinal cracks by using a vacuum impregnation process; Before the vacuum impregnation process is used to fill the heat absorbing material into the longitudinal crack, the method further comprises: The kaolin is processed by high temperature treatment, acid treatment and ultrasonic dispersion treatment in sequence to obtain nano-grade kaolin; Mixing nano-sized kaolin with a liquid to obtain a heat absorbing material; The method of filling the longitudinal crack with the heat absorbing material by a vacuum impregnation process comprises: Place the thermal insulation layer in a vacuum negative pressure environment; Covering the heat absorbing material on the entire upper portion of the heat insulation layer; Applying positive pressure to the heat absorbing material and performing ultrasonic dispersion treatment; The heat absorbing material is made to fill the longitudinal crack.

2. The preparation method according to claim 1, characterized in that: The liquid includes water; After allowing the heat absorbing material to fill the longitudinal crack, the method further comprises: The water in some longitudinal cracks is evaporated by controlling the temperature, humidity and heating time.

3. The preparation method according to claim 1, characterized in that: The liquid includes a salt solution; wherein the salt solution includes a phosphate solution, a chloride solution and a fluoride solution; After allowing the heat absorbing material to fill the longitudinal crack, the method further comprises: Prepare a salt solution with a concentration lower than the preset concentration; The water in the salt solution in some longitudinal cracks is evaporated by controlling the temperature, humidity and heating time, so that the concentration of the salt solution is a preset concentration.

4. The preparation method according to claim 1, characterized in that: The volume of the longitudinal cracks accounts for 20-30% of the volume of the thermal insulation layer.

5. The preparation method according to claim 1, characterized in that: The longitudinal depth of the longitudinal crack is not less than 65-90% of the thickness of the thermal insulation layer.

6. The preparation method according to claim 1, characterized in that: The heat absorbing material comprises at least one of a fatty acid solid-liquid phase change material and an alcohol solid-liquid phase change material; The method of filling the longitudinal crack with the heat absorbing material by a vacuum impregnation process comprises: Heating the solid-liquid phase change material in a vacuum environment to make it in liquid phase; The heat insulation layer is soaked with a liquid solid-liquid phase change material, and a positive pressure is applied to the liquid solid-liquid phase change material so that the liquid solid-liquid phase change material is immersed in the longitudinal crack; After the longitudinal cracks are filled, they are taken out after the temperature and pressure are reduced.

7. The preparation method according to claim 1, characterized in that: The method of spraying the slurry on the substrate to be protected by an ion spraying process to obtain a heat insulation layer with longitudinal cracks comprises: The slurry including a plurality of vacuum balls is sprayed on the substrate to be protected by using an ion spraying process to obtain a heat insulation layer with longitudinal cracks and vacuum balls.

8. The preparation method according to claim 7, characterized in that: The shell of the vacuum ball is made of silicon dioxide and / or aluminum oxide, and the outer diameter of the vacuum ball is 5 to 10 μm.

9. The preparation method according to claim 1, characterized in that: After the heat absorbing material is filled into the longitudinal crack by the vacuum impregnation process, the method further comprises: A sealing layer is prepared by plasma spraying on the side of the thermal insulation layer away from the protective substrate; wherein the preparation material of the sealing layer includes the thermal barrier material, and the sealing layer is used to seal the opening of the longitudinal crack located on the surface of the thermal insulation layer; The thickness of the heat insulation layer is 50-500 μm, and the thickness of the sealing layer is 5-20 μm.

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