Method for improving the bonding force and life of thermal barrier coating of rocket copper thrust chamber by heat treatment

Abstract

This invention relates to the field of heat treatment technology for metallic materials, specifically a method for improving the adhesion and lifespan of a thermal barrier coating in a rocket's copper thrust chamber through heat treatment. The key technical points include the following steps: S1, spraying Cu-based alloy powder onto the surface of a copper alloy substrate using atmospheric plasma spraying technology; S2, performing intermediate heat treatment; S3, spraying Ni-based alloy powder using atmospheric plasma spraying technology; S4, spraying MCrAlX alloy powder using atmospheric plasma spraying technology; S5, performing thermal diffusion treatment; and S6, performing aging heat treatment. This invention utilizes low-cost atmospheric plasma spraying technology to prepare a metallic thermal barrier coating, and combines this with heat treatment to improve the adhesion quality between the coating and the substrate, as well as between the coating interfaces, while retaining the high strength and high hardness of the copper alloy substrate. This improves the thermal cycle life of the metallic thermal barrier coating under conditions with large temperature gradients and the lifespan of the rocket engine's copper alloy thrust chamber.

Description

Technical Field

[0001] This invention relates to the field of heat treatment technology for metallic materials, and specifically to a method for improving the adhesion and lifespan of the thermal barrier coating in the copper thrust chamber of a rocket through heat treatment. Background Technology

[0002] Rocket engine thrust chambers are typically constructed from copper alloys with high strength and high thermal conductivity. However, in actual service, copper alloy thrust chambers are highly susceptible to deformation and failure under the harsh operating environment of high temperature, high pressure, and high heat flux density, as well as the large internal thermal stress caused by large temperature gradients. Therefore, NASA first proposed preparing a metallic thermal barrier coating on the inner wall of the copper alloy to reduce the temperature gradient and thus improve the service life of the copper alloy.

[0003] Atmospheric plasma spraying technology, with its advantages of operating in atmospheric conditions, low operating costs, no restrictions on the size of the workpiece, and excellent adhesion between the coating and the substrate, has become the preferred technology for preparing thermal barrier coatings for copper alloy thrust chambers and is widely used in actual production. However, the current technology for preparing metal thermal barrier coatings for copper alloy thrust chambers using atmospheric plasma spraying still faces two major bottlenecks, which seriously restrict the service performance of the coating and the safe operation of the thrust chamber.

[0004] On the one hand, there are significant compositional differences and mismatches in linear expansion coefficients between the sprayed metal coating and the copper alloy substrate. This makes it easy for high residual stress to be generated at the coating-substrate interface during the coating preparation process. Simultaneously, copper alloys have extremely high thermal conductivity. When molten sprayed metal particles are deposited on the surface of the copper alloy substrate, heat is rapidly dissipated through the substrate, resulting in excessively fast particle cooling. This prevents the formation of an effective bonding interface between the coating and the substrate, weakening the interfacial bonding strength. As the coating thickness increases, the residual stress at the interface continues to accumulate. When the stress value exceeds the bonding strength threshold between the coating and the substrate, it easily leads to coating delamination, peeling, and other failure phenomena, severely affecting the service reliability of the metal thermal barrier coating.

[0005] On the other hand, the high strength and hardness of copper alloys used in rocket engine thrust chambers (such as chromium-zirconium copper and chromium bronze) are primarily due to the aging strengthening effect. After aging treatment, a large number of finely dispersed second-phase particles precipitate in the copper matrix. These particles effectively hinder dislocation movement, thus achieving a significant precipitation strengthening effect. It is crucial to note that if the heat treatment process parameters are not properly controlled, such as excessively high heat treatment temperatures (exceeding the suitable aging temperature, typically above 450℃) or excessively long holding times, the originally uniformly dispersed fine second-phase particles will significantly coarsen and aggregate, even forming large, blocky precipitates. Their hindering effect on dislocations will be greatly reduced, significantly decreasing the precipitation strengthening effect and consequently leading to a significant decrease in the hardness and strength of the copper alloy matrix. Furthermore, excessive heat treatment can cause some precipitated phases to redissolve in the copper matrix, reducing the number of effective strengthening phases and further weakening the mechanical properties of the matrix. Because the inner wall of the copper alloy thrust chamber is used in extreme environments with large temperature gradients for a long time, if the strength of the matrix is ​​greatly reduced due to improper heat treatment, the repeated action of thermal stress during service will easily cause plastic deformation and structural failure of the copper alloy thrust chamber, which will lead to serious safety hazards such as coolant leakage, directly threatening the safe and stable operation and service life of the rocket engine.

[0006] In summary, optimizing the heat treatment process to effectively improve the bonding quality between the coating and the substrate, as well as the interface within the coating, while maximizing the preservation of the high strength and hardness of the copper alloy substrate remains a core technical challenge that urgently needs to be overcome in the fields of thermal spraying and aerospace engines. To address these issues, this application proposes a method for improving the adhesion and lifespan of the thermal barrier coating in the copper thrust chamber of rockets through heat treatment. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention provides a method for improving the adhesion and lifespan of thermal barrier coatings in rocket copper thrust chambers through heat treatment, thus solving the problems mentioned in the background art.

[0008] The above-mentioned technical objective of the present invention is achieved through the following technical solution: A method for improving the adhesion and lifespan of a thermal barrier coating in a rocket's copper thrust chamber through heat treatment includes the following steps: S1. Cu-based alloy powder material is sprayed onto the surface of a copper alloy substrate using atmospheric plasma spraying technology to obtain a Cu-based metal bonding layer. S2. The Cu-based metal bonding layer is subjected to intermediate heat treatment to eliminate residual stress in the coating and achieve bonding between the coating and the copper alloy substrate through micro-diffusion, thereby improving the bonding strength. S3. Ni-based alloy powder material is sprayed onto the surface of the Cu-based metal bonding layer after heat treatment in step S2 using atmospheric plasma spraying technology to obtain the Ni-based metal bonding layer. S4. MCrAlX alloy powder material is sprayed onto the surface of the Ni-based adhesive layer using atmospheric plasma spraying technology to obtain a metal heat insulation layer, forming a metal thermal barrier coating with a three-layer structure. S5. Perform thermal diffusion treatment on the metal thermal barrier coating to form a metallurgical bond between the coatings and between the coating and the substrate, thereby improving the coating bonding strength. S6. The metal thermal barrier coating after step S5 is subjected to aging heat treatment to precipitate the second phase and restore the mechanical properties of the copper alloy matrix.

[0009] Preferably, the heat treatment in steps S2, S5 and S6 is carried out in a vacuum environment or a protective atmosphere, wherein the protective atmosphere is hydrogen or argon.

[0010] Preferably, the heating rate in steps S2 and S5 is 2°C / min to 6°C / min, and the cooling method is furnace cooling.

[0011] Preferably, in step S2, the intermediate heat treatment temperature is 750℃~850℃, and the holding time is 0.5h~1.5h.

[0012] Preferably, in step S2, the intermediate heat treatment temperature is 800℃ and the holding time is 0.5h.

[0013] Preferably, in step S5, the temperature of the heat diffusion treatment is 750℃~850℃, and the holding time is 1.5h~3h.

[0014] Preferably, in step S5, the temperature of the heat diffusion treatment is 800°C and the holding time is 2 hours.

[0015] Preferably, in step S6, the temperature of the aging heat treatment is 400℃~550℃, and the holding time is 4h~12h.

[0016] Preferably, in step S6, the aging heat treatment temperature is 450°C and the holding time is 10 hours.

[0017] In summary, the present invention has the following main beneficial effects: This invention effectively eliminates residual stress introduced in the early stages of preparation and improves the bonding strength between the Cu-based adhesive layer and the copper alloy substrate by performing stress annealing and micro-diffusion treatment immediately after the Cu-based metal binder layer is prepared, thus preventing delamination of the coating during subsequent thickening. Subsequent high-temperature thermal diffusion treatment of the metal thermal barrier coating ensures sufficient metallurgical bonding within the three-layer coating system and between interfaces, increasing the bonding strength from the traditional approximately 30 MPa to over 80 MPa. Experimental data shows that the thermal cycle life of the metal thermal barrier coating treated by this invention is significantly increased from approximately 80 cycles to 150-250 cycles, greatly improving the service reliability of rocket engine thrust chambers.

[0018] This invention utilizes an aging process to solve the problem of substrate softening caused by high-temperature diffusion. Although the hardness of the copper alloy substrate decreases during the high-temperature thermal diffusion stage, the subsequent precisely controlled aging heat treatment steps can promote the re-dispersion and precipitation of second-phase particles, allowing the substrate hardness to be completely restored from the softened 80HV to the initial 180HV level. This ensures both excellent bonding quality of the coating and sufficient strength of the substrate to resist thermal stress deformation during service. This invention not only realizes the high-quality application of low-cost atmospheric plasma spraying technology, but also has important strategic and industrial value for ensuring the safe operation of heavy-lift launch vehicles and promoting deep space exploration. Attached Figure Description

[0019] Figure 1 This is a flowchart of the heat treatment method of the present invention; Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments. Based on the described embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] The following embodiments are used to illustrate the present invention, but should not be used to limit the scope of protection of the present invention. The conditions in the embodiments can be further adjusted according to specific conditions, and simple improvements to the method of the present invention under the premise of the concept of the present invention are all within the scope of protection claimed by the present invention.

[0022] Example 1: This embodiment provides a method for improving the adhesion and lifespan of the thermal barrier coating in a rocket's copper thrust chamber through heat treatment. The steps are as follows: Figure 1 As shown, the steps are as follows: S1: A Cu-based alloy powder coating is prepared on the surface of a copper alloy substrate using atmospheric plasma spraying technology to obtain a Cu-based metal bonding layer.

[0023] S2: Heat treatment is performed on the Cu-based adhesive layer to eliminate residual stress in the coating and achieve bonding between the coating and the substrate through micro-diffusion, thereby improving the bonding strength. The heat treatment conditions are: heating rate of 2℃ / min, temperature of 800℃, and holding time of 0.5 hours.

[0024] S3: Ni-based alloy powder material is sprayed onto the surface of the Cu-based adhesive layer to obtain a second Ni-based adhesive layer.

[0025] S4: MCrAlX alloy powder is sprayed onto the surface of the Ni-based adhesive layer to obtain a metal heat insulation layer.

[0026] S5: Perform thermal diffusion treatment on the coating to form a metallurgical bond between the coatings and between the coating and the substrate, thereby improving the bonding strength. The thermal diffusion treatment is carried out in a vacuum or atmosphere-protected heat treatment furnace with a heating rate of 2℃ / min, a heat treatment temperature of 800℃, and a holding time of 2 hours.

[0027] S6: The metal thermal barrier coating after step S5 is subjected to aging heat treatment to precipitate the second phase and restore the mechanical properties of the copper alloy matrix. The aging heat treatment temperature is 450℃ and the holding time is 10 hours.

[0028] The test results are shown in the table below:

[0029] The table above shows that: Improved bonding strength: By adopting an intermediate heat treatment process, the residual stress between the coating and the substrate was successfully eliminated, and the bonding strength was improved by micro-diffusion technology, increasing the bonding strength from 30MPa to 50MPa, showing a significant improvement.

[0030] Extended thermal cycling life: The thermal cycling life of the coating has increased from about 80 cycles to 150-250 cycles, indicating that the stability and durability of the coating in high-temperature environments have been significantly improved.

[0031] The properties of the copper alloy matrix are maintained: the aging heat treatment effectively restores the hardness of the copper alloy matrix, ensuring the stable operation of the thrust chamber under high temperature and high pressure conditions.

[0032] In summary, the heat treatment method of this embodiment can ensure high bonding strength between the coating and the copper alloy substrate while maximizing the preservation of the strength and hardness of the copper alloy substrate, thereby significantly improving the thermal cycle life of the metal thermal barrier coating, extending the service life of the rocket's copper alloy thrust chamber, and improving its reliability and stability in harsh environments.

[0033] Example 2: This embodiment provides a method for improving the adhesion and lifespan of the thermal barrier coating in a rocket's copper thrust chamber through heat treatment. The steps are as follows: S1: A Cu-based alloy powder layer is prepared on the surface of a copper alloy substrate using atmospheric plasma spraying technology to obtain a Cu-based metal bonding layer.

[0034] S2: Heat treatment is performed on the Cu-based adhesive layer to eliminate residual stress in the coating and achieve bonding between the coating and the substrate through micro-diffusion. The heat treatment conditions are: heating rate of 2℃ / min, temperature of 800℃, and holding time of 0.5 hours.

[0035] S3: Ni-based alloy powder material is sprayed onto the surface of the Cu-based adhesive layer to obtain a second Ni-based adhesive layer.

[0036] S4: MCrAlX alloy powder is sprayed onto the surface of the Ni-based adhesive layer to obtain a metal heat insulation layer.

[0037] S5: Perform thermal diffusion treatment on the coating to form a metallurgical bond between the coatings and between the coating and the substrate, thereby improving the bonding strength. The thermal diffusion treatment is carried out in a vacuum or atmosphere-protected heat treatment furnace with a heating rate of 2℃ / min, a heat treatment temperature of 800℃, and a holding time of 2 hours.

[0038] S6: The metal thermal barrier coating after step S5 is subjected to aging heat treatment to precipitate the second phase and restore the mechanical properties of the copper alloy matrix. The aging heat treatment temperature is 450℃ and the holding time is 10 hours.

[0039] Thermal cycling life test conditions: Thermal cycling life test of the coating was carried out using laser equipment. The surface of the coating was heated by laser to raise the surface temperature to 1000℃ in 0.1s and maintained at this temperature for 2s before heating was stopped. At the same time, compressed air was used to strongly cool the back of the sample, so that a large temperature gradient could be generated rapidly inside the coating.

[0040] The test results are shown in the table below:

[0041] The table above shows that: The bonding strength of the coating is significantly improved: the bonding strength between the heat-treated coating and the substrate is significantly improved, increasing from 28 MPa to 52 MPa, indicating that the bonding quality between the coating and the substrate has been greatly improved.

[0042] Significantly extended thermal cycling life: In thermal cycling tests conducted under large temperature gradient environments, the thermal cycling life of the coating increased from approximately 70 cycles to 200-250 cycles, indicating a significant improvement in the stability and durability of the coating.

[0043] Copper alloy matrix performance retention: Aging heat treatment effectively restores the hardness of the copper alloy matrix, ensuring the structural strength and stability of the thrust chamber under high temperature conditions.

[0044] In summary, this embodiment verifies the effectiveness of the method of the present invention under large temperature gradient environments. In particular, under extreme high temperature conditions, the coating exhibits excellent performance in terms of bonding strength, thermal cycle life, and mechanical properties of the copper alloy substrate. The bonding strength between the coating and the substrate is significantly improved, and the coating does not delaminate or peel off at high temperatures, which greatly enhances the service life and safety of the rocket thrust chamber.

[0045] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that, unless otherwise defined, the technical or scientific terms used in this invention should be understood in the ordinary sense by those skilled in the art to which this invention pertains, and the terms "comprising" or "including" or similar terms used in this invention mean that the element or object preceding the word covers the element or object listed after the word and its equivalents.

[0046] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for improving the adhesion and lifespan of a thermal barrier coating in a rocket's copper thrust chamber through heat treatment, characterized in that, Includes the following steps: S1. Using atmospheric plasma spraying technology, Cu-based alloy powder material is sprayed onto the surface of a copper alloy substrate to obtain a Cu-based metal bonding layer. S2. The Cu-based metal bonding layer is subjected to intermediate heat treatment to eliminate residual stress in the coating and achieve bonding between the coating and the copper alloy substrate through micro-diffusion, thereby improving the bonding strength. S3. Ni-based alloy powder material is sprayed onto the surface of the Cu-based metal bonding layer after heat treatment in step S2 using atmospheric plasma spraying technology to obtain the Ni-based metal bonding layer. S4. MCrAlX alloy powder material is sprayed onto the surface of the Ni-based adhesive layer using atmospheric plasma spraying technology to obtain a metal heat insulation layer, forming a metal thermal barrier coating with a three-layer structure. S5. Perform thermal diffusion treatment on the metal thermal barrier coating to form a metallurgical bond between the coatings and between the coating and the substrate, thereby improving the coating bonding strength. S6. The metal thermal barrier coating after step S5 is subjected to aging heat treatment to precipitate the second phase and restore the mechanical properties of the copper alloy matrix.

2. The method for improving the adhesion and lifespan of the thermal barrier coating in a rocket's copper thrust chamber through heat treatment according to claim 1, characterized in that, The heat treatments in steps S2, S5, and S6 are all carried out in a vacuum environment or a protective atmosphere, wherein the protective atmosphere is hydrogen or argon.

3. The method for improving the adhesion and lifespan of the thermal barrier coating in a rocket's copper thrust chamber through heat treatment according to claim 1, characterized in that, The heating rate in steps S2 and S5 is 2℃ / min to 6℃ / min, and the cooling method is furnace cooling.

4. The method for improving the adhesion and lifespan of the thermal barrier coating in a rocket's copper thrust chamber through heat treatment according to claim 1, characterized in that, In step S2, the intermediate heat treatment temperature is 750℃~850℃, and the holding time is 0.5h~1.5h.

5. The method for improving the bonding strength and lifespan of the thermal barrier coating in a rocket copper alloy thrust chamber by heat treatment according to claim 1, characterized in that, In step S2, the intermediate heat treatment temperature is 800℃ and the holding time is 0.5h.

6. The method for improving the adhesion and lifespan of the thermal barrier coating in a rocket's copper thrust chamber through heat treatment according to claim 1, characterized in that, In step S5, the temperature of the heat diffusion treatment is 750℃~850℃, and the holding time is 1.5h~3h.

7. The method for improving the adhesion and lifespan of the thermal barrier coating in a rocket's copper thrust chamber through heat treatment according to claim 1, characterized in that, In step S5, the temperature of the heat diffusion treatment is 800℃ and the holding time is 2h.

8. The method for improving the adhesion and lifespan of the thermal barrier coating in a rocket's copper thrust chamber through heat treatment according to claim 1, characterized in that, In step S6, the aging heat treatment temperature is 400℃~550℃, and the holding time is 4h~12h.

9. The method for improving the adhesion and lifespan of the thermal barrier coating in a rocket's copper thrust chamber through heat treatment according to claim 1, characterized in that, In step S6, the aging heat treatment temperature is 450℃ and the holding time is 10h.

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