High-reflection thermal protection coating and preparation method thereof

Abstract

The invention relates to the technical field of thermal protection coatings, and discloses a high-reflection thermal protection coating and a preparation method thereof.LSTN0.125 powder is subjected to spray granulation and then pre-sintered and sieved, and spherical LSTN0.125 ceramic powder is obtained; the alloy substrate is subjected to roughening treatment, and a bonding layer is prepared on the surface of the alloy substrate through the atmosphere plasma spraying technology; the spherical LSTN0.125 ceramic powder obtained in the step S1 is sprayed on the bonding layer through the atmosphere plasma spraying technology, and an LSTN0.125 ceramic layer is obtained; and the LSTN0.125 ceramic layer is subjected to heat treatment, and the LSTN0.125 thermal protection coating is obtained. According to the invention, the LSTN0.125 with high reflectivity is used as a powder raw material of the coating, so that the high reflection performance of the coating in a near-infrared band can be remarkably enhanced, and the effect of isolating high temperature is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of thermal protection coatings, and in particular to a highly reflective thermal protection coating and a preparation method thereof. Background Art

[0002] In fields such as aerospace and high-temperature industrial equipment, thermal protection coatings are crucial for ensuring stable operation in extremely high-temperature environments. Currently, radiative heat transfer is a key method of heat transfer in high-temperature environments. Therefore, developing thermal protection coatings that can effectively block radiative heat transfer is of great practical significance.

[0003] Ion spraying is often used in existing technologies to prepare highly reflective thermal protective coatings. However, the high-temperature plasma environment causes complex physical and chemical changes in the powder material, which easily generates oxygen vacancies. The appearance of oxygen vacancies will have many adverse effects on the performance of the coating. On the one hand, oxygen vacancies will change the optical properties of the coating, reduce its reflectivity in the near-infrared band, and reduce the coating's ability to block radiant heat; on the other hand, the presence of oxygen vacancies will also affect the chemical stability and mechanical properties of the coating, making the coating prone to cracking, peeling, and other problems, thereby shortening the service life of the coating and failing to meet the demand for high-reliability thermal protective coatings in practical applications.

[0004] Therefore, there is an urgent need for a highly reflective thermal protective coating and a preparation method thereof to solve the above technical problems. Summary of the Invention

[0005] The purpose of the present invention is to overcome the existing technical problems and provide a highly reflective thermal protective coating and a preparation method thereof.

[0006] To achieve the above object, the present invention is implemented according to the following technical solutions:

[0007] A method for preparing a highly reflective thermal protective coating comprises the following steps:

[0008] S1, for LSTN 0.125 The powder is spray granulated, then pre-sintered and sieved to obtain spherical LSTN 0.125 Ceramic powder;

[0009] S2, roughening the alloy substrate and preparing a bonding layer on the surface of the alloy substrate using atmospheric plasma spraying technology (APS for short);

[0010] S3, using atmospheric plasma spraying technology to spray the spherical LSTN obtained in step S1 on the bonding layer obtained in step S2 0.125 Ceramic powder, get LSTN 0.125 Ceramic layer;

[0011] S4, the obtained LSTN 0.125 The ceramic layer is heat treated to obtain LSTN 0.125 Thermal protective coating.

[0012] LSTN in the present invention 0.125 The chemical formula of the powder is La 0.9 Sr 0.1 Ti 0.875 Nb 0.125 O 3+δ .

[0013] It can be prepared by the following preparation method:

[0014] (1) La2O3, SrCO3, TiO2 and Nb2O5 were prepared in a molar ratio of 36:8:70:5 and added to a ball mill. Anhydrous ethanol and zirconium oxide grinding balls were then added, with a mass ratio of balls: materials: anhydrous ethanol of 3:1:1. The ball mill was placed in a planetary ball mill and milled at a speed of 500 rpm for 18 h to obtain a uniformly mixed ball mill slurry.

[0015] (2) The ball mill slurry was transferred to a rotary evaporator to remove ethanol. The rotary evaporator was heated to 80°C. The powder was then placed in a box-type drying furnace and dried at 150°C for 10 to 24 hours to obtain a uniformly mixed dry powder.

[0016] (3) The dried powder was placed in a sintering furnace and kept at 1400 °C for 6 h. It was then ground and sieved to obtain La 0.9 Sr 0.1 Ti 0.875 Nb 0.125 O 3+δ Ceramic powder material, referred to as LSTN 0.125 Powder material.

[0017] Preferably, in step S1, the pre-sintering process is: keeping the temperature at 800-900° C. for 2 hours.

[0018] Preferably, in step S1, the spherical LSTN 0.125 The particle size of the ceramic powder is 30 to 80 μm.

[0019] Specifically, step S1 includes the following steps:

[0020] S1, for LSTN 0.125 The powder is spray granulated, and then the granulated powder is pre-sintered, degreased and sieved to obtain spherical LSTN 0.125 Ceramic powder.

[0021] Preferably, in step S1, the spray granulation process: LSTN0.125 Ceramic powder and deionized water are loaded into a nylon ball mill at a mass ratio of 6.5:3.5, and 1.5-2.5% of a polyvinyl alcohol binder (PVA) by mass of the ceramic powder and 1% of a polyacrylate ammonium dispersant (PAA) by mass of the ceramic powder are added, and the mixture is ball milled together with zirconium oxide grinding balls for 12 hours to obtain a slurry for spray granulation. The mixed slurry is passed into a spray granulator, and the process parameters of the spray granulator are as follows: a feed rate of 50 ml / min, an atomization pressure of 0.05 MPa, an air inlet temperature of 200-280°C, and an air outlet temperature of 100°C.

[0022] Preferably, in step S2, the roughness of the alloy substrate subjected to the roughening treatment is 5 to 10 μm.

[0023] Preferably, in step S2, before preparing the bonding layer on the alloy surface, the roughened alloy substrate is preheated to 240°C.

[0024] Preferably, in step S2, the parameters for spraying the bonding layer using atmospheric plasma technology are: spraying distance 90-110 mm, spraying power 28-30 kW, argon flow rate 40-45 SLPM, hydrogen flow rate 5-7 SLPM, carrier gas flow rate 5-7 SLPM, and bonding layer thickness 120-150 μm.

[0025] Preferably, in step S2, the bonding layer is a NiCrCoAlY bonding layer; and the alloy substrate is a stainless steel substrate.

[0026] The NiCrCoAlY bonding layer in the present invention is prior art, and those skilled in the art are aware of its composition.

[0027] Specifically, step S2 includes the following steps:

[0028] S2, the alloy substrate is roughened using a sandblasting machine, and a NiCrCoAlY bonding layer is prepared on the surface of the alloy substrate using atmospheric plasma spraying technology (APS).

[0029] Preferably, in step S3, LSTN is sprayed using atmospheric plasma technology. 0.125 The parameters of the ceramic layer are: spraying distance 90-110mm, spraying power 30-33kW, argon flow rate 40-45SLPM, hydrogen flow rate 8-12SLPM, carrier gas flow rate 10-12SLPM, protective atmosphere oxygen flow rate 30SLPM, the LSTN 0.125 The thickness of the ceramic layer is 130 to 160 μm.

[0030] Preferably, in step S4, the heat treatment process is at 900° C. and kept warm for 1 hour.

[0031] The equipment used in the present invention for spraying the corresponding coating using atmospheric plasma technology is Shanghai Dahao-DH-2080 atmospheric plasma spraying equipment.

[0032] The present invention also includes a highly reflective thermal protection coating prepared by the above preparation method.

[0033] Working principle:

[0034] The present invention adopts La 0.9 Sr 0.1 Ti 0.875 Nb 0.125 O 3+δ (abbreviated as LSTN 0.125 ) Ceramic powder material as raw material for thermal protective coating; LSTN 0.125 Due to its unique crystal structure and optical properties, ceramic powder materials exhibit high reflectivity in the near-infrared band, effectively blocking heat generated by radiation. Thermal protection coatings made from this material provide excellent thermal protection for substrates in high-temperature environments, reducing heat transfer to the substrate, thereby improving equipment reliability and service life.

[0035] LSTN is prepared by plasma spraying commonly used in existing technology 0.125 Thermal protective coatings are prone to generate oxygen vacancies, which leads to reduced near-infrared reflectivity and poor thermal protection performance of the coating. Therefore, the present invention provides a method for effectively reducing the generation of oxygen vacancies for LSTN. 0.125 Thermal protective coating and its preparation method. By optimizing and improving the preparation process, LSTN can be reduced. 0.125 The oxygen vacancies in the thermal protective coating improve its reflectivity in the near-infrared band, thereby preparing LSTN with high reflectivity 0.125 Thermal protective coatings can better block the heat generated by radiation, improve the thermal protection effect and comprehensive performance of the coating, and meet the needs of aerospace, high-temperature industrial equipment and other fields for high-performance thermal protective coatings.

[0036] The main creativity of this invention is that it is the first time to use APS technology to prepare LSTN 0.125 Ceramic layer, due to the extremely high operating temperature of APS and a certain amount of kinetic energy, eventually leading to LSTN 0.125 The oxygen vacancy content of the thermal protective coating increases and the reflectivity decreases. The present invention optimizes the process parameters of the spraying and sprays LSTN. 0.125 In the process of ceramic layer, oxygen is added as a protective atmosphere and the ceramic layer is heat treated to ensure LSTN 0.125 Thermal protective coating and LSTN 0.125The powder material has consistent performance and maintains high reflectivity, and finally a LSTN with high reflectivity is prepared. 0.125 Thermal protective coating. In the method provided by the present invention, step S1 is to prepare spherical LSTN by spray granulation technology. 0.125 Ceramic powder can increase the deposition rate of the ceramic layer; the bonding layer prepared by APS technology in step S2 can enhance the bonding strength between the subsequent ceramic layer and the alloy substrate; step S3 adjusts the APS parameters to prepare LSTN 0.125 Ceramic layer, step S4 heat treats the ceramic layer, wherein steps S3 and S4 are for maintaining high reflectivity LSTN 0.125 The preparation of thermal protective coatings is crucial.

[0037] Beneficial effects:

[0038] (1) Using LSTN with high reflectivity 0.125 As the powder raw material of the coating, it can significantly enhance the high reflectivity of the coating in the near-infrared band and play a role in isolating high temperatures;

[0039] (2) By optimizing APS technology, using oxygen as a protective atmosphere, and heat treating the coating, the LSTN obtained 0.125 Compared with the powder raw material, the thermal protective coating retains its excellent high reflectivity performance, with a reflectivity of up to 85%; at the same time, the coating has excellent thermal protection effect. When the coating surface reaches 900°C, the temperature on the back of the coating is only 720°C, and the comprehensive thermal insulation protection capacity reaches 20%, which has broad application prospects in the field of thermal protective coatings. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 LSTN obtained in Example 1, Example 2 and Comparative Example 1 of the present invention 0.125 XRD pattern of thermal protective coating;

[0041] Figure 2 LSTN obtained in Example 1 and Example 2 of the present invention 0.125 Ceramic layer and LSTN prepared in Comparative Example 1 0.125 Reflectance spectrum of the coating in the visible-near infrared band;

[0042] Figure 3 LSTN obtained in Example 1 and Comparative Example 2 of the present invention 0.125 Reflectance maps of thermal protective coatings in the visible and near-infrared bands;

[0043] Figure 4 LSTN obtained in Example 1 of the present invention 0.125 Thermal insulation performance curve of thermal protective coating. DETAILED DESCRIPTION

[0044] The present invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0045] There is no particular limitation on the purity of all raw materials in the present invention. The present invention preferably uses industrial purity or conventional purity used in the art.

[0046] The devices used in the present invention are not particularly limited and can be devices commonly used in the art.

[0047] In the following embodiments, the equipment used to prepare the corresponding coatings using the APS technology is Shanghai Dahao-DH-2080 atmospheric plasma spraying equipment.

[0048] The LSTN used in the following examples and comparative examples 0.125 The chemical formula of the powder is La 0.9 Sr 0.1 Ti 0.875 Nb 0.125 O 3+δ , which is prepared by the following preparation method:

[0049] (1) La2O3, SrCO3, TiO2, and Nb2O5 were prepared in a molar ratio of 36:8:70:5 and added to a ball mill. Anhydrous ethanol and zirconium oxide grinding balls were then added, with a mass ratio of balls:material:anhydrous ethanol of 3:1:1. The ball mill was placed in a planetary ball mill and milled at a speed of 500 rpm for 18 h to obtain a uniformly mixed slurry.

[0050] (2) The ball mill slurry was transferred to a rotary evaporator to remove ethanol. The rotary evaporator was heated to 80°C. The powder was then placed in a box-type drying furnace and dried at 150°C for 10 minutes to obtain a uniformly mixed dry powder.

[0051] (3) The dried powder was placed in a sintering furnace and kept at 1400 °C for 6 h. It was then ground and sieved to obtain La 0.9 Sr 0.1 Ti 0.875 Nb 0.125 O 3+δ Ceramic powder material, referred to as LSTN 0.125 Powder material.

[0052] Example 1

[0053] A method for preparing a highly reflective thermal protective coating comprises the following steps:

[0054] S1, for LSTN 0.125After the powder is spray granulated, it is degreased at a pre-sintering temperature of 900°C and kept warm for 2 hours; then spherical LSTN with a particle size of 30 to 80 μm is selected through screening. 0.125 Ceramic powder;

[0055] Spray granulation process: LSTN 0.125 Ceramic powder and deionized water were loaded into a nylon ball mill at a mass ratio of 6.5:3.5. A polyvinyl alcohol binder (PVA) at a concentration of 2% by mass of the ceramic powder and a polyacrylate ammonium dispersant (PAA) at a concentration of 1% by mass of the ceramic powder were added. The mixture was ball milled with zirconium oxide grinding balls for 12 hours to obtain a slurry for spray granulation. The mixed slurry was passed into a spray granulator with the following process parameters: a feed rate of 50 ml / min, an atomizing pressure of 0.05 MPa, an air inlet temperature of 250-260°C, and an air outlet temperature of 100°C.

[0056] S2, a stainless steel substrate was sandblasted to a roughness of 10 μm. The substrate was preheated to 240°C, and an APS coating of NiCrCoAlY was applied. The coating parameters were: spray distance 110 mm, spray power 30 kW, argon flow rate 45 SLPM, hydrogen flow rate 7 SLPM, carrier gas flow rate 7 SLPM, and the bonding layer thickness was controlled to 150 μm.

[0057] S3, using APS technology to spray the spherical LSTN obtained in step S1 on the NiCrCoAlY bonding layer in step S2 0.125 Ceramic powder; spraying parameters are: spraying distance 110mm, spraying power 33kW, argon flow 45SLPM, hydrogen flow 12SLPM, carrier gas flow 12SLPM, protective atmosphere oxygen flow 30SLPM, LSTN 0.125 The thickness of the ceramic layer is 130 μm;

[0058] S4, the prepared LSTN 0.125 The ceramic layer is heat treated at 900℃ for 1 hour to obtain the final LSTN 0.125 Thermal protective coating.

[0059] Example 2

[0060] A method for preparing a highly reflective thermal protective coating comprises the following steps:

[0061] S1, for LSTN 0.125 The powder is spray granulated and placed in a high-temperature furnace for degreasing at a pre-sintering temperature of 800°C for 2 hours. After cooling, the powder is screened using a sieve to select spherical LSTN with a particle size of 30 to 80 μm. 0.125 Ceramic powder;

[0062] Spray granulation process: LSTN 0.125 Ceramic powder and deionized water were loaded into a nylon ball mill at a mass ratio of 6.5:3.5. A polyvinyl alcohol binder (PVA) at a concentration of 2% by mass of the ceramic powder and a polyacrylate ammonium dispersant (PAA) at a concentration of 1% by mass of the ceramic powder were added. The mixture was ball milled with zirconium oxide grinding balls for 12 hours to obtain a slurry for spray granulation. The mixed slurry was passed into a spray granulator with the following process parameters: a feed rate of 50 ml / min, an atomizing pressure of 0.05 MPa, an air inlet temperature of 250-260°C, and an air outlet temperature of 100°C.

[0063] S2, using a sandblaster to roughen the stainless steel substrate to a roughness of 5 μm; after preheating the substrate to 240°C, atmospheric plasma spraying (APS) was used to deposit a NiCrCoAlY bonding layer on the substrate surface; the specific preparation parameters were: spraying distance 90 mm, spraying power 28 kW, argon flow rate 40 SLPM, hydrogen flow rate 5 SLPM, and carrier gas flow rate 5 SLPM; the resulting NiCrCoAlY bonding layer had a thickness of 120 μm;

[0064] S3, using APS technology to spray the spherical LSTN obtained in step S1 on the NiCrCoAlY bonding layer obtained in step S2 0.125 Ceramic powder; spraying parameters are set as follows: spraying distance 90mm, spraying power 30kW, argon flow rate 40SLPM, hydrogen flow rate 8SLPM, carrier gas flow rate 10SLPM, protective atmosphere oxygen flow rate 30SLPM, and the obtained LSTN 0.125 The thickness of the ceramic layer is 160 μm;

[0065] S4, the obtained LSTN 0.125 The ceramic layer is placed in a heat treatment furnace and heat treated at 900°C for 1 hour to obtain LSTN. 0.125 Thermal protective coating.

[0066] Comparative Example 1

[0067] S1, for LSTN 0.125 The powder is spray granulated and then pre-sintered and degreased at 850℃ for 2h. Spherical LSTN with a particle size of 30-80μm is selected through screening. 0.125 Ceramic powder;

[0068] Spray granulation process: LSTN 0.125Ceramic powder and deionized water were loaded into a nylon ball mill at a mass ratio of 6.5:3.5. A polyvinyl alcohol binder (PVA) at a concentration of 2% by mass of the ceramic powder and a polyacrylate ammonium dispersant (PAA) at a concentration of 1% by mass of the ceramic powder were added. The mixture was ball milled with zirconium oxide grinding balls for 12 hours to obtain a slurry for spray granulation. The mixed slurry was passed into a spray granulator with the following process parameters: a feed rate of 50 ml / min, an atomizing pressure of 0.05 MPa, an air inlet temperature of 250-260°C, and an air outlet temperature of 100°C.

[0069] S2: The stainless steel substrate was sandblasted to a roughness of 7 μm. After preheating to 240°C, an APS technique was used to deposit a NiCrCoAlY bonding layer. The parameters were: spray distance 100 mm, spray power 29 kW, argon flow rate 42 SLPM, hydrogen flow rate 6 SLPM, carrier gas flow rate 6 SLPM, and a bonding layer thickness of 135 μm.

[0070] S3, on the bonding layer of step S2, use APS technology to spray the spherical LSTN of step S1 0.125 Ceramic powder; spraying parameters are: spraying distance 100mm, spraying power 33kW, argon flow 42SLPM, hydrogen flow 10SLPM, carrier gas flow 11SLPM, LSTN 0.125 The thickness of the ceramic layer is 150 μm.

[0071] Comparative Example 2

[0072] S1, for LSTN 0.125 After the powder is spray granulated, it is degreased at a pre-sintering temperature of 900°C and kept warm for 2 hours. Then, spherical LSTN0.125 ceramic powder with a particle size of 30 to 80 μm is screened.

[0073] Spray granulation process: LSTN 0.125 Ceramic powder and deionized water were loaded into a nylon ball mill at a mass ratio of 6.5:3.5. A polyvinyl alcohol binder (PVA) at a concentration of 2% by mass of the ceramic powder and a polyacrylate ammonium dispersant (PAA) at a concentration of 1% by mass of the ceramic powder were added. The mixture was ball milled with zirconium oxide grinding balls for 12 hours to obtain a slurry for spray granulation. The mixed slurry was passed into a spray granulator with the following process parameters: a feed rate of 50 ml / min, an atomizing pressure of 0.05 MPa, an air inlet temperature of 250-260°C, and an air outlet temperature of 100°C.

[0074] S2, a stainless steel substrate was sandblasted to a roughness of 10 μm. The substrate was preheated to 240°C, and an APS coating of NiCrCoAlY was applied. The coating parameters were: spray distance 110 mm, spray power 30 kW, argon flow rate 45 SLPM, hydrogen flow rate 7 SLPM, carrier gas flow rate 7 SLPM, and the bonding layer thickness was controlled to 150 μm.

[0075] S3, using APS technology to spray the spherical LSTN0.125 ceramic powder obtained in step S1 on the NiCrCoAlY bonding layer of step S2; the spraying parameters are: spraying distance 110mm, spraying power 36kW, argon flow rate 45SLPM, hydrogen flow rate 12SLPM, carrier gas flow rate 12SLPM, protective atmosphere oxygen flow rate 30SLPM, LSTN 0.125 The thickness of the ceramic layer is 130 μm.

[0076] like Figure 1 As shown, Figure 1 LSTN obtained in Example 1, Example 2 and Comparative Example 1 of the present invention 0.125 XRD pattern of thermal protective coating. LSTN in the figure 0.125 -Powder refers to LSTN 0.125 Powder.

[0077] Depend on Figure 1 It can be seen that the phase of the coating prepared in Example is similar to that of LSTN 0.125 The powders are basically the same. However, the diffraction peak of the phase of Comparative Example 1 is not obvious, and the crystallinity is poor.

[0078] like Figure 2 As shown, the LSTN obtained in Example 1 and Example 2 of the present invention 0.125 Ceramic layer and LSTN prepared in Comparative Example 1 0.125 Reflectance spectrum of the coating in the visible-near-infrared band.

[0079] Depend on Figure 2 It can be seen that the LSTN prepared in the embodiment 0.125 Ceramic layer (LSTN without heat treatment 0.125 The reflectivity of the thermal protective coating is much higher than that of the comparative example, indicating the necessity of introducing oxygen as a protective atmosphere in step S3.

[0080] like Figure 3 As shown, the LSTN obtained in Example 1 and Comparative Example 2 of the present invention 0.125 The reflectivity diagram of the thermal protective coating in the visible light and near-infrared bands; the figure also shows the LSTN obtained in Example 1 and Comparative Example 2 0.125 Samples of thermal protective coatings.

[0081] Depend on Figure 3 It can be seen that the coating of Example 1 has LSTN after the heat treatment in step S4. 0.125 The average reflectivity in the visible-near infrared band is about 85%. Compared with Example 1, the coating of Comparative Example 2 has a reflectivity much lower than that of Example 1 because it does not undergo the heat treatment of step S4.

[0082] like Figure 4 As shown, the LSTN obtained in Example 1 of the present invention 0.125 Thermal insulation performance curve of thermal protective coating.

[0083] Depend on Figure 4 It can be seen that LSTN 0.125 The temperature on the back of the thermal protection coating is significantly lower than that of the LSTN 0.125 The surface temperature of the thermal protective coating is 0.125 When the surface temperature of the thermal protective coating is 900°C, the temperature on the back of the coating is only 720°C, with a temperature reduction of up to 20%. It has excellent application prospects in the field of thermal protective coatings.

[0084] The technical solution of the present invention is not limited to the above-mentioned specific embodiments. Any technical variations made according to the technical solution of the present invention fall within the protection scope of the present invention.

Claims

1. A method for preparing a highly reflective thermal protective coating, characterized in that: The following steps are involved: S1, for LSTN 0.125 The powder is spray granulated, then pre-sintered and sieved to obtain spherical LSTN 0.125 Ceramic powder; S2, roughening the alloy substrate and preparing a bonding layer on the surface of the alloy substrate using atmospheric plasma spraying technology; S3, using atmospheric plasma spraying technology to spray the spherical LSTN obtained in step S1 on the bonding layer obtained in step S2 0.125 Ceramic powder, get LSTN 0.125 Ceramic layer; S4, the obtained LSTN 0.125 The ceramic layer is heat treated to obtain LSTN 0.125 Thermal protective coating.

2. The method for preparing a highly reflective thermal protective coating according to claim 1, wherein: In step S1, the pre-sintering process is: keeping the temperature at 800-900° C. for 2 hours.

3. The method for preparing a highly reflective thermal protective coating according to claim 1, wherein: In step S1, the spherical LSTN 0.125 The particle size of the ceramic powder is 30 to 80 μm.

4. The method for preparing a highly reflective thermal protective coating according to claim 1, wherein: In the step S2, the roughness of the alloy substrate subjected to the roughening treatment is 5 to 10 μm.

5. The method for preparing a highly reflective thermal protective coating according to claim 1, wherein: In the step S2, before preparing the bonding layer on the alloy surface, the roughened alloy substrate is preheated to 240°C.

6. The method for preparing a highly reflective thermal protective coating according to claim 1, wherein: In step S2, the parameters for spraying the bonding layer using atmospheric plasma technology are: spraying distance 90-110 mm, spraying power 28-30 kW, argon flow rate 40-45 SLPM, hydrogen flow rate 5-7 SLPM, carrier gas flow rate 5-7 SLPM, and bonding layer thickness 120-150 μm.

7. The method for preparing a highly reflective thermal protective coating according to claim 1, wherein: In step S2, the bonding layer is a NiCrCoAlY bonding layer; and the alloy substrate is a stainless steel substrate.

8. The method for preparing a highly reflective thermal protective coating according to claim 1, wherein: In step S3, LSTN is sprayed using atmospheric plasma technology. 0.125 The parameters of the ceramic layer are: spraying distance 90-110 mm, spraying power 30-33 kW, argon flow rate 40-45 SLPM, hydrogen flow rate 8-12 SLPM, carrier gas flow rate 10-12 SLPM, protective atmosphere flow rate 30 SLPM, protective atmosphere is oxygen, the LSTN 0.125 The thickness of the ceramic layer is 130 to 160 μm.

9. The method for preparing a highly reflective thermal protective coating according to claim 1, wherein: In step S4, the heat treatment process is at 900° C. and kept warm for 1 hour.

10. A highly reflective thermal protective coating prepared by the preparation method according to any one of claims 1 to 9.

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