A method of producing a high-entropy carbide coating by thermal spraying in combination with methane carburization

Abstract

A method and coating for preparing a high-entropy carbide coating by thermal spraying combined with methane carbonization are disclosed. The method includes: substrate pretreatment, which involves cleaning and roughening the substrate surface, and sealing pores if necessary, to remove impurities and prevent interlayer delamination; mixed powder preparation, in which high-entropy alloy powder and phenolic resin powder are mixed in a specific ratio to obtain a mixed powder, wherein the high-entropy alloy comprises at least five elemental metal powders; thermal spraying process, in which the mixed powder is heated to a molten or semi-molten state under an argon atmosphere and sprayed onto the pretreated substrate surface to form a coating; and in-situ carbonization treatment, in which the coating is subjected to a carbonization reaction for 6-10 hours under conditions of a methane to argon volume ratio of 3.5:1 to 4.5:1, a pressure of 0.1-0.5 MPa, and a temperature of 1400-2000℃, allowing the high-entropy alloy to fully react with the carbon source methane to generate the final high-entropy carbide ceramic coating.

Description

Technical Field

[0001] This invention relates to the field of coating materials technology, and in particular to a method and coating for preparing high-entropy carbide coatings by thermal spraying combined with methane carbonization. Background Technology

[0002] In the field of coating materials technology, thermal spraying technology is widely used due to its unique advantages. This technology involves heating the coating material to a molten or semi-molten state, atomizing it with a high-speed airflow, and spraying it onto the substrate surface. After condensation, a coating with specific functions is formed. However, traditional thermal spraying technology faces many insurmountable problems in coating preparation. From the perspective of coating density, its inherent porosity is high. Thermal spray coatings are formed by countless molten or semi-molten deformed particles stacked in a wave-like pattern. In atmospheric spraying, the particles oxidize with the surrounding medium, and due to differences in flight speed and temperature, gaps or pores easily form between the stacked particles. During cooling and solidification, if the gas cannot escape in time, or if the particles shrink without being replenished by the liquid phase, pores will be generated. The porosity of ordinary flame spraying reaches 10%~20%, and that of arc spraying is about 10%. High porosity severely reduces the hardness, wear resistance, and corrosion resistance of the coating, and also weakens the bonding strength between the coating and the substrate and within the coating itself, greatly affecting the service life of the coating. Furthermore, existing processes have extremely limited range for adjusting coating density, making it difficult to prepare highly dense coatings. High-entropy carbide ceramics, as a promising new type of material, have attracted much attention in extreme environment applications such as aerospace and nuclear industry. Traditional high-entropy carbide ceramics preparation typically uses transition metal carbides, such as TiC, ZrC, HfC, and NbC, as starting materials. However, the melting points of these transition metal carbides generally exceed 3000℃, posing a significant challenge to the preparation process. Taking traditional thermal spraying heat sources as an example, the HVOF flame temperature is approximately 3000K, making it difficult to ensure uniform melting of all components. While plasma spraying can achieve even higher temperatures, it faces the challenge of complex process control. In practice, due to the inability to ensure uniform melting of all components, the properties of the prepared high-entropy carbide ceramics are inconsistent, failing to meet the requirements of high-end applications for material performance consistency and stability. Moreover, the high-temperature melting process consumes a great deal of energy, which not only increases production costs but also limits the large-scale application of this technology. In the process of preparing high-entropy carbide ceramics by thermal spraying, carbides readily react with oxygen at high temperatures. Carbides such as TiC and ZrC react with oxygen to form oxides such as TiO2 and ZrO2. This reaction not only causes the coating composition to deviate from the expected design, severely affecting the coating performance, but may also form brittle phases, reducing the coating's toughness and impact resistance. This makes the coating prone to failure phenomena such as cracking and peeling during use, greatly limiting the application of high-entropy carbide ceramic coatings in practical engineering. The information disclosed in the background section is only for enhancing the understanding of the background of this invention, and therefore may contain information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0003] This invention provides a method and coating for preparing high-entropy carbide coatings using thermal spraying combined with methane carbonization. The method employs a composite spraying of high-entropy alloy and phenolic resin powder combined with in-situ methane carbonization. Utilizing the volume expansion effect during high-entropy alloy carbonization, the method simultaneously eliminates porosity generated by phenolic resin decomposition and fills inherent pores in the thermal spraying process, achieving wide-range control of porosity and improved coating density. Introducing methane gas further optimizes the preparation environment, reducing the reaction of carbides with oxygen at high temperatures. This effectively avoids excessive oxide formation, ensuring the coating composition meets expectations, reducing the formation of brittle phases, thereby guaranteeing or even improving coating quality. No additional anti-oxidation treatment is required, further saving costs.

[0004] A method for preparing a high-entropy carbide coating by thermal spraying combined with methane carbide formation includes: Substrate pretreatment involves cleaning and roughening the substrate surface, and sealing pores if necessary, to remove impurities and prevent interlayer delamination. Mixed powder preparation: A high-entropy alloy is mixed with phenolic resin powder with a residual carbon rate of ≥30% in a certain proportion to obtain a mixed powder, wherein the high-entropy alloy contains at least five or more elemental metal powders; Thermal spraying process involves heating mixed powder to a molten or semi-molten state under an argon atmosphere and spraying it onto the surface of a pretreated substrate to form a coating. In-situ carbonization treatment involves subjecting the coating to a carbonization reaction for 6 to 10 hours under conditions of a methane to argon volume ratio of 3.5:1 to 4.5:1, a pressure of 0.1 to 0.5 MPa, and a temperature of 1400 to 2000 °C. This allows the high-entropy alloy to fully react with the carbon source methane, resulting in the final high-entropy carbide ceramic coating.

[0005] The method for preparing a high-entropy carbide coating by thermal spraying combined with methane carbonization is characterized in that the substrate is graphite or carbon / carbon composite material, and the surface needs to be cleaned by mechanical blowing or organic solvents to remove impurities such as oil and dust to ensure the cleanliness of the substrate. Then, the surface roughness is increased by sandblasting to improve the coating adhesion. If necessary, a special sealant is used to seal the surface pores to prevent gas from escaping or penetrating during spraying and affecting the coating quality.

[0006] The method for preparing a high-entropy carbide coating by thermal spraying combined with methane carburization is characterized in that the high-entropy alloy is selected from any five or more combinations of Ti, Zr, Hf, Ta, Nb, and Mo, and mixed in an equimolar ratio.

[0007] The method for preparing a high-entropy carbide coating by thermal spraying combined with methane carbonization is characterized in that the phenolic resin powder has a particle size of 80~95μm.

[0008] The method for preparing a high-entropy carbide coating by thermal spraying combined with methane carbonization is characterized in that high-entropy alloy powder and phenolic resin powder are weighed in a ratio of (7:3) to (9:1) using an electronic balance, poured into a V-type vacuum mixer, sealed, and evacuated to 0.08MPa to 0.1MPa. The mixing is started with a rotation speed of 30 to 60 rpm and a mixing time of 360 to 480 minutes. After the mixing is completed, the gas is released and the equipment is opened to obtain the mixed powder.

[0009] The method for preparing a high-entropy carbide coating by thermal spraying combined with methane carbonization is characterized by using an atmospheric plasma spraying device for thermal spraying. The parameters are set as follows: argon flow rate 30-50 L / min, spray current 100-200 A, voltage 60-120 V, powder feed rate 10-30 g / min, spray gun moving speed 100-200 mm / s, and spraying distance 100-150 mm. The mixed powder is heated to a molten or semi-molten state and sprayed onto the substrate surface to form a coating. Finally, the coating is held at 800°C for 2 hours in an argon atmosphere to optimize its performance.

[0010] The method for preparing a high-entropy carbide coating by thermal spraying combined with methane carbonization is characterized in that the particle size difference between the phenolic resin powder and the high-entropy alloy powder is ≤5μm.

[0011] The method for preparing a high-entropy carbide coating by thermal spraying combined with methane carbonization is characterized in that, during the in-situ carbonization treatment, the pore structure inside the coating buffers 20% to 25% of the volume expansion during the carbonization reaction.

[0012] A method for preparing a high-entropy carbide coating by thermal spraying combined with methane carbonization is disclosed, which is based on the preparation method of high-entropy carbide ceramic coating.

[0013] The high-entropy carbide ceramic coating has a porosity of ≤3%, and includes high-entropy carbide MC, wherein M is a combination of at least five or more elements selected from Ti, Zr, Hf, Ta, Nb, and Mo, and the coating surface and interior are free of oxide phases.

[0014] Compared with existing technologies, this invention has the following advantages: This invention utilizes thermal spraying technology combined with phenolic resin-assisted in-situ carbonization to prepare high-entropy carbide ceramic coatings, achieving significant results. In terms of process efficiency and cost, thermal spraying offers rapid deposition, allows for large-area application, and is suitable for industrial production. Simultaneously, phenolic resin replaces some high-cost carbon sources, reducing expenses. Microstructure control is optimized; phenolic resin decomposes pores to enhance methane permeability, while rapid cooling during thermal spraying suppresses segregation, achieving atomic-level mixing. Coating performance is significantly improved; the high-entropy effect synergistically results in dense carbides, enhancing ablation resistance and high-temperature stability, while pores buffer carbonization expansion to prevent cracking. Furthermore, thermal spraying is not limited by molds and can be applied to complex-shaped substrates, meeting diverse needs.

[0015] This preparation technology boasts significant advantages, including high efficiency and low cost, rapid deposition rate that reduces costs, strong microstructure control capability, optimized carbonization and composition uniformity, excellent performance to meet high-temperature applications, and strong adaptability to complex shapes, thus broadening its application range. However, the technology also has drawbacks. While thermal spraying is a mature technology, the combination of phenolic resin-assisted in-situ carbonization increases the complexity of the process, requiring strict control of parameters at each stage to ensure coating quality. Attached Figure Description

[0016] Various other advantages and benefits of the present invention will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiments below. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. It is obvious that the drawings described below are merely some embodiments of the invention, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort. Furthermore, the same reference numerals denote the same parts throughout the drawings.

[0017] In the attached diagram: Figure 1 SEM image of the mixed powder; Figure 2 SEM image of the cross-section of the coating before methane carbonization; Figure 3 SEM image and energy dispersive spectroscopy (EDS) of the cross-section of the coating after methane carbonization; Figure 4 XRD patterns of the coatings before and after carbonization; Figure 5 This is a SEM image of the cross-section of a comparative high-entropy carbide ceramic coating.

[0018] The present invention will be further explained below with reference to the accompanying drawings and embodiments. Detailed Implementation

[0019] Specific embodiments of the invention will now be described in more detail with reference to the accompanying drawings. While specific embodiments of the invention are shown in the drawings, it should be understood that the invention may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this invention will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

[0020] It should be noted that certain terms are used in the specification and claims to refer to specific components. Those skilled in the art will understand that different terms may be used to refer to the same component. This specification and claims do not distinguish components based on differences in terminology, but rather on differences in function. The terms "comprising" or "including" used throughout the specification and claims are open-ended and should be interpreted as "comprising but not limited to." The following descriptions are preferred embodiments for carrying out the invention; however, these descriptions are for the purpose of understanding the general principles of the specification and are not intended to limit the scope of the invention. The scope of protection of this invention is determined by the appended claims.

[0021] To facilitate understanding of the embodiments of the present invention, further explanations and descriptions will be provided below with reference to the accompanying drawings and specific embodiments. The accompanying drawings do not constitute a limitation on the embodiments of the present invention.

[0022] like Figures 1 to 4 As shown, the preparation method of high-entropy carbide ceramic coating includes the following steps: Substrate pretreatment involves cleaning and roughening the substrate surface, and sealing pores if necessary, to remove impurities and prevent interlayer delamination. The mixed powder is prepared by mixing a high-entropy alloy with phenolic resin powder having a residual carbon content ≥30% in a certain proportion. The high-entropy alloy contains at least five or more elemental metal powders. Thermal spraying process involves heating mixed powder to a molten or semi-molten state under an argon atmosphere and spraying it onto the surface of a pretreated substrate to form a coating. In-situ carbonization is performed under conditions of methane to argon volume ratio of 3.5:1 to 4.5:1, pressure of 0.1 to 0.5 MPa, and temperature of 1400 to 2000℃. The coating undergoes a carbonization reaction for 6 to 10 hours, allowing the high-entropy alloy to fully react with the carbon source methane, generating the final high-entropy carbide ceramic coating. High-entropy carbide ceramic coatings refer to multi-component ceramic coatings composed of five or more metallic elements and carbon. High-entropy alloys are alloy materials prepared by alloying five or more elements in equiatomic ratios or close to equiatomic ratios; they are also known as multi-principal-element high-entropy alloys, whose mixing entropy is higher than the alloy's melting entropy. High-entropy alloys break through the traditional design concept of alloys based on one or two metallic elements. In traditional alloys, adding more metal species often leads to the precipitation of large amounts of complex, brittle intermetallic compounds or intermediate phases. However, high-entropy alloys tend to form simple body-centered cubic or face-centered cubic phases after solidification. The mutual solid solution of numerous different types of atoms results in severe lattice distortion, leading to a strong solid solution strengthening effect. Furthermore, depending on the heat treatment conditions, a certain amount of dispersed second phases, such as intermetallic structural phases, nanophases, and amorphous phases, may be generated during cooling or annealing, resulting in second-phase dispersion strengthening. High-entropy alloys exhibit excellent properties such as high hardness, high work hardening, resistance to high-temperature softening, corrosion resistance, and high electrical resistance. Some high-entropy alloys have a higher specific strength than traditional alloys, and also demonstrate superior fracture resistance, tensile strength, corrosion resistance, and oxidation resistance.

[0023] The method for preparing a high-entropy carbide coating by thermal spraying combined with methane carbonization is characterized in that the substrate is graphite or carbon / carbon composite material, and the surface needs to be cleaned by mechanical blowing or organic solvents to remove impurities such as oil and dust to ensure the cleanliness of the substrate. Then, the surface roughness is increased by sandblasting to improve the coating adhesion. If necessary, a special sealant is used to seal the surface pores to prevent gas from escaping or penetrating during spraying and affecting the coating quality.

[0024] The method for preparing a high-entropy carbide coating by thermal spraying combined with methane carburization is characterized in that the high-entropy alloy is selected from any five or more combinations of Ti, Zr, Hf, Ta, Nb, and Mo, and mixed in an equimolar ratio.

[0025] The method for preparing a high-entropy carbide coating by thermal spraying combined with methane carbonization is characterized in that the phenolic resin powder has a particle size of 80~95μm.

[0026] The method for preparing a high-entropy carbide coating by thermal spraying combined with methane carbonization is characterized in that high-entropy alloy powder and phenolic resin powder are weighed in a ratio of (7:3) to (9:1) using an electronic balance, poured into a V-type vacuum mixer, sealed, and evacuated to 0.08MPa to 0.1MPa. The mixing is started with a rotation speed of 30 to 60 rpm and a mixing time of 360 to 480 minutes. After the mixing is completed, the gas is released and the equipment is opened to obtain the mixed powder.

[0027] The method for preparing a high-entropy carbide coating by thermal spraying combined with methane carbonization is characterized by using an atmospheric plasma spraying device for thermal spraying. The parameters are set as follows: argon flow rate 30-50 L / min, spray current 100-200 A, voltage 60-120 V, powder feed rate 10-30 g / min, spray gun moving speed 100-200 mm / s, and spraying distance 100-150 mm. The mixed powder is heated to a molten or semi-molten state and sprayed onto the substrate surface to form a coating. Finally, the coating is held at 800°C for 2 hours in an argon atmosphere to optimize its performance.

[0028] The method for preparing a high-entropy carbide coating by thermal spraying combined with methane carbonization is characterized in that the particle size difference between the phenolic resin powder and the high-entropy alloy powder is ≤5μm.

[0029] The method for preparing a high-entropy carbide coating by thermal spraying combined with methane carbonization is characterized in that, during the in-situ carbonization treatment, the pore structure inside the coating buffers 20% to 25% of the volume expansion during the carbonization reaction.

[0030] A method for preparing a high-entropy carbide coating by thermal spraying combined with methane carbonization is disclosed, which is based on the preparation method of high-entropy carbide ceramic coating.

[0031] In one embodiment, the coating exhibits ablation resistance with a mass loss rate ≤0.5 mg / s at 2000°C. The coating is suitable for complex curved substrates, with a thickness uniformity deviation ≤10%.

[0032] In a preferred embodiment of the high-entropy carbide ceramic coating, the porosity of the high-entropy carbide ceramic coating is ≤3%, the high-entropy carbide ceramic coating includes high-entropy carbide MC, wherein M is a combination of at least five elements selected from Ti, Zr, Hf, Ta, Nb, and Mo, and the coating surface and interior are free of oxide phases.

[0033] In one embodiment, the method includes, Step 1, Pretreatment of substrate surface: The surface of the graphite or carbon / carbon composite substrate is cleaned by mechanical blowing or organic solvents to remove impurities such as oil and dust, ensuring the substrate is clean. Then, the surface roughness is increased by sandblasting to improve the coating adhesion. If necessary, a special sealant is used to seal the surface pores to prevent gas from escaping or penetrating during spraying and affecting the coating quality, thus obtaining the pretreated substrate.

[0034] Step 2, Raw material selection and pretreatment Commercially available high-entropy alloy powder, containing elements such as Ti, Zr, Hf, Ta, Nb, and Mo (any 5 or more, mixed in an equimolar ratio), and phenolic resin with a residual carbon content >30%, are used to control the particle size to 80-95 μm, matching the particle size of the high-entropy alloy. The powder is accurately weighed using an electronic balance at a ratio of (7:3) to (9:1) and poured into a V-type vacuum mixer. The mixer is sealed and evacuated to 0.08 MPa-0.1 MPa. The mixing speed is set to 30-60 rpm and the mixing time to 360-480 minutes. Mixing is started while observing the mixing process and adjusting as needed. After mixing, the gas is released and the equipment is opened to obtain a mixed powder of refractory high-entropy alloy and phenolic resin.

[0035] Step 3, Thermal spraying process: An atmospheric plasma spraying device was used, with parameters set as follows: argon flow rate 30~50L / min, spray current 100~200A, voltage 60~120V, powder feeding rate 10~30g / min, spray gun moving speed 100~200mm / s, and spraying distance 100~150mm. The mixed powder prepared in step 2 was heated to a molten or semi-molten state and sprayed onto the substrate surface to form a coating. Finally, the coating was kept at 800℃ for 2 hours in an argon atmosphere to optimize the coating performance.

[0036] Step 4, in-situ carbonization: The sprayed coating is placed in a specific environment for in-situ carbonization. A gas mixture of methane (CH4) and hydrogen (H2) at a volume ratio of 3.5:1 to 4.5:1 is used as the reaction atmosphere. The gas pressure is controlled at 0.1 to 0.5 MPa, and the temperature is raised to 1400 to 2000℃ and maintained under these conditions for 6 to 10 hours to ensure complete carbonization. During this process, the phenolic resin undergoes pyrolysis to generate amorphous carbon, which accounts for 20% to 40% of the final carbon content, serving as an important supplementary carbon source. The porous structure within the coating effectively buffers the 20% to 25% volume expansion during carbonization, preventing coating cracking.

[0037] Example 1:

[0038] Step 1, Matrix Pretreatment Select a graphite or carbon / carbon composite matrix, and clean the surface of the matrix by mechanical blowing or organic solvent to remove impurities such as oil and dust to ensure the matrix is ​​clean. Then, sandblasting is used to increase the surface roughness to improve the coating adhesion. If necessary, a special sealant is used to seal the surface pores to prevent gas from escaping or penetrating during spraying and affecting the coating quality. This will give you the pretreated matrix.

[0039] Step 2, Preparation of mixed powders Commercially available high-entropy alloy powders of Ti, Zr, Hf, Ta, and Nb (in equimolar ratio) were mixed with phenolic resin having a residual carbon content >30%, ensuring the particle size was controlled to approximately 95 μm to match the high-entropy alloy particle size. The high-entropy alloy and phenolic resin were accurately weighed using an electronic balance at a mass ratio of 9:1 and poured into a V-type vacuum mixer. The mixer was sealed and evacuated to 0.1 MPa. The mixing speed was set to 50 rpm and the mixing time to 400 minutes. The mixing process was observed and adjusted as needed. After completion, the gas was released and the equipment was opened to obtain a mixed powder of refractory high-entropy alloy and phenolic resin.

[0040] Step 3, Thermal spraying process An atmospheric plasma spraying device was used, with parameters set as follows: argon flow rate 40L / min, spray current 150A, voltage 90V, powder feeding rate 20g / min, spray gun moving speed 150mm / s, and spraying distance 120mm. The mixed powder prepared in step 2 was heated to a molten or semi-molten state and sprayed onto the substrate surface to form a coating. Finally, the coating was kept at 800℃ for 2 hours in an argon atmosphere to optimize the coating performance.

[0041] Step 4, in-situ carbonization The sprayed coating was placed in a specific environment for in-situ carbonization. A gas mixture of methane (CH4) and hydrogen (H2) at a volume ratio of 4.5:1 was used as the reaction atmosphere, with the pressure controlled at 0.3 MPa and the temperature raised to 1800℃. This temperature was maintained for 3 hours to ensure complete carbonization. During this process, the phenolic resin pyrolyzes to generate amorphous carbon, which accounts for 30% of the final carbon content and serves as an important supplementary carbon source. The porous structure within the coating effectively buffers the 25% volume expansion during carbonization, preventing coating cracking.

[0042] Results: The coating porosity was ≤2.5%, and there was no oxide phase inside.

[0043] Example 2: Replacement of high-entropy alloy group The only difference from Example 1 is: High-entropy alloy composition: Zr, Hf, Ta, Nb, Mo (replace Ti with Mo).

[0044] Carbonization parameters: Temperature 1900℃, holding time 2.5h.

[0045] Effect: The coating's high-temperature ablation resistance is at 4MW / m 2 The ablation rate of the linear ablation line under an oxyacetylene flame at 3000℃ for 120s is ≤10μm / s.

[0046] Step 1, Matrix Pretreatment Select a graphite or carbon / carbon composite matrix, and clean the surface of the matrix by mechanical blowing or organic solvent to remove impurities such as oil and dust to ensure the matrix is ​​clean. Then, sandblasting is used to increase the surface roughness to improve the coating adhesion. If necessary, a special sealant is used to seal the surface pores to prevent gas from escaping or penetrating during spraying and affecting the coating quality. This will give you the pretreated matrix.

[0047] Step 2, Preparation of mixed powders Commercially available high-entropy alloy powders of Ti, Zr, Hf, Ta, and Mo (in equimolar ratio) were mixed. Phenolic resin with a residual carbon content >30% was selected to control the particle size to approximately 95 μm, matching the particle size of the high-entropy alloy. The high-entropy alloy and phenolic resin were accurately weighed using an electronic balance at a mass ratio of 9:1 and poured into a V-type vacuum mixer. The mixer was sealed and evacuated to 0.1 MPa. The mixing speed was set to 50 rpm and the mixing time to 400 minutes. The mixing process was observed and adjusted as needed. After completion, the gas was released and the equipment was opened to obtain a mixed powder of refractory high-entropy alloy and phenolic resin.

[0048] Step 3, Thermal spraying process An atmospheric plasma spraying device was used, with parameters set as follows: argon flow rate 40L / min, spray current 150A, voltage 90V, powder feeding rate 20g / min, spray gun moving speed 150mm / s, and spraying distance 120mm. The mixed powder prepared in step 2 was heated to a molten or semi-molten state and sprayed onto the substrate surface to form a coating. Finally, the coating was kept at 800℃ for 2 hours in an argon atmosphere to optimize the coating performance.

[0049] Step 4, in-situ carbonization The sprayed coating was placed in a specific environment for in-situ carbonization. A gas mixture of methane (CH4) and hydrogen (H2) at a volume ratio of 4.5:1 was used as the reaction atmosphere, with the pressure controlled at 0.3 MPa and the temperature raised to 1900℃. This temperature was maintained for 2.5 hours to ensure complete carbonization. During this process, the phenolic resin pyrolyzes to generate amorphous carbon, which accounts for 30% of the final carbon content and serves as an important supplementary carbon source. The porous structure within the coating effectively buffers the 25% volume expansion during carbonization, preventing coating cracking.

[0050] Example 3: Optimization of Particle Size Matching for Mixed Powders The difference from Example 1 is as follows: Powder particle size control: The particle size difference between high-entropy alloy and phenolic resin is ≤3μm (alloy 85μm, resin 82μm).

[0051] Mixing process: vacuum degree 0.08MPa, rotation speed 60 rpm, mixing time 480 minutes.

[0052] Results: The high-entropy alloy coating has a more uniform pore distribution, and the porosity after carbonization is ≤2.5%.

[0053] Example 4: Fine-tuning of spraying parameters The difference from Example 1 is as follows: Spraying parameters: Argon gas 50L / min, current 200A, voltage 120V, powder feeding rate 30g / min, spray gun moving speed 200mm / s.

[0054] Results: Spray deposition rate increased by 30%, coating thickness uniformity deviation ≤8%.

[0055] Example 5: Low-pressure carbonization process The difference from Example 1 is as follows: Carbonization parameters: pressure 0.1MPa, temperature 1600℃, holding time 4h.

[0056] Results: The volume expansion rate was 25%, the pores were completely filled, and no cracks were generated.

[0057] Example 6: Performance Verification of High-Entropy Carbide Coating Coating inspection: XRD patterns ( Figure 4 : Only MC phase (e.g., (Ti,Zr,Hf,Ta,Nb)C) is displayed, with no extraneous peaks.

[0058] SEM morphology ( Figure 3 ): The cross-section is dense, and the porosity is ≤3%.

[0059] Performance testing: High-temperature ablation resistance: Under 4MW / m2 and 3000℃ oxyacetylene flame, the linear ablation rate after 120s is ≤10μm / s.

[0060] Comparative Example 1 (Counterexample): Phenolic resin omitted Step 2 Adjustment: Use only the high-entropy alloy powder from Example 1.

[0061] Carbonization results: XRD patterns ( Figure 5 The results show that no carbides were formed inside the coating, with only slight surface carbonization. This indicates that the coating, lacking the carbonization channels provided by the phenolic resin, only achieved surface carbonization, making it impossible to prepare a carbide ceramic coating that meets the required conditions.

[0062] Comparative Example 2 (Comparison with Traditional Processes) Method: Direct plasma spraying of commercially available high-entropy carbide powder (Ti, Zr, Hf, Ta, Nb)C.

[0063] Parameters: Same as the spraying conditions in Example 1.

[0064] Results: SEM morphology ( Figure 5 The results show a porosity >10% and obvious delamination. It is evident that certain pores and delamination exist within and on the surface of the coating. These pores and delaminations are formed due to the different flight velocities and temperatures of the molten droplets, resulting in varying spreading states after impacting the substrate. Consequently, the layers cannot adhere completely, making this defect unavoidable in plasma spraying.

[0065] This invention uses graphite or carbon / carbon composite materials as the matrix. The matrix surface is cleaned by mechanical blowing or organic solvents to remove oil, dust, and other impurities, ensuring matrix cleanliness. Subsequently, sandblasting is used to increase surface roughness to improve coating adhesion. If necessary, a special sealant is used to seal surface pores to prevent gas escape or penetration during spraying, which could affect coating quality. It promotes uniform mixing: similar particle sizes (≤5μm difference from phenolic resin) reduce gravitational segregation, ensuring compositional consistency during spraying. Phenolic resin with a residual carbon content ≥30% is added and mixed with the alloy at a mass ratio (1:9~3:7), and vacuum-mixed for 360~480 minutes. It provides a dispersed carbon source: resin pyrolysis generates amorphous carbon (accounting for 20%~40% of the final carbon content), which serves as a supplementary carbon source in the carbonization reaction, compensating for insufficient carbon supply in areas with insufficient methane penetration. It forms initial pores: resin decomposition produces 10%~20% porosity, providing channels for subsequent methane gas penetration and accelerating carbonization reaction kinetics. Buffering volume expansion: The resin decomposition pores can accommodate 20%~25% volume expansion during the carburization of high-entropy alloys, preventing coating cracking. Atmospheric plasma spraying: Argon gas 30~50L / min, current 100~200A, spraying distance 100~150mm, followed by argon gas incubation at 800℃ for 2h. Suppressing elemental segregation: High cooling rate (>10) 6 K / s) freezes atomic diffusion in molten droplets, maintaining the uniformity of high-entropy alloy composition and avoiding elemental segregation (such as Mo enrichment) in traditional sintering. Methane (CH4) and hydrogen (H2) are mixed at a volume ratio of 3.5:1 to 4.5:1, pressure 0.1 to 0.5 MPa, temperature 1600 to 2000℃, and held for 2 to 4 hours. Controllable carbon potential environment: H2 acts as a reducing agent to prevent free carbon (carbon deposits) from high-temperature cracking of methane, while adjusting carbon activity (ac = 0.8 to 1.2) to ensure the forward carbonization reaction. Figure 4XRD shows no free carbon peaks. Temperature: 1400~2000℃, holding time: 6~19h. Promotes solid-state reaction: At high temperature, the solid-state diffusion coefficient of high-entropy alloys and carbon is increased, and the reaction rate is increased by 3~5 times, achieving complete carbonization. Balances densification and expansion: At temperature >1800℃, volume expansion (15%~20%) and resin pore filling work synergistically, resulting in a final porosity ≤3%.

[0066] This invention achieves dynamic porosity control through a triple synergy of high-entropy alloy + phenolic resin composite powder design, rapid densification via thermal spraying, and methane carbonization: initial porosity (resin decomposition) → carbonization expansion and filling → final densification (≤3% porosity). The reaction of carbides with oxygen at high temperatures effectively avoids excessive oxide formation, reduces the formation of brittle phases, eliminates the need for additional anti-oxidation treatment, further saving costs, and the coating's high-temperature stability (no oxidation at 2000℃) is superior to traditional processes. Adaptability to complex shapes: The non-contact deposition of thermal spraying combined with the self-compensating effect of carbonization volume ensures that the coating thickness deviation on complex substrates such as curved surfaces and internal cavities is ≤10%.

[0067] Although embodiments of the present invention have been described above in conjunction with the accompanying drawings, the present invention is not limited to the specific embodiments and application fields described above. The specific embodiments described above are merely illustrative and instructive, and not restrictive. Those skilled in the art can make many other forms based on the guidance of this specification and without departing from the scope of protection of the claims of the present invention, and all of these are within the scope of protection of the present invention.

Claims

1. A method for preparing a high-entropy carbide coating by thermal spraying combined with methane carbonization, characterized in that, Includes the following steps: Substrate pretreatment involves cleaning and roughening the substrate surface, and sealing pores if necessary, to remove impurities and prevent interlayer delamination. Mixed powder preparation: High-entropy alloy and phenolic resin powder are mixed in a certain proportion to obtain mixed powder, wherein the high-entropy alloy contains at least five or more elemental metal powders. Thermal spraying process involves heating mixed powder to a molten or semi-molten state under an argon atmosphere and spraying it onto the surface of a pretreated substrate to form a coating. In-situ carbonization treatment involves subjecting the coating to a carbonization reaction for 6 to 10 hours under conditions of a methane to argon volume ratio of 3.5:1 to 4.5:1, a pressure of 0.1 to 0.5 MPa, and a temperature of 1400 to 2000 °C. This allows the high-entropy alloy to fully react with the carbon source methane, resulting in the final high-entropy carbide ceramic coating.

2. The method for preparing a high-entropy carbide coating by thermal spraying combined with methane carbonization according to claim 1, characterized in that, Preferably, the substrate is graphite or carbon / carbon composite material. The surface needs to be cleaned by mechanical blowing or organic solvents to remove impurities such as oil and dust to ensure the substrate is clean. Then, sandblasting is used to increase the surface roughness to improve the coating adhesion. If necessary, a special sealant is used to seal the surface pores to prevent gas from escaping or penetrating during spraying and affecting the coating quality.

3. The method for preparing a high-entropy carbide coating by thermal spraying combined with methane carbonization according to claim 1, characterized in that, The high-entropy alloy is selected from any five or more combinations of Ti, Zr, Hf, Ta, Nb, and Mo, and mixed in an equimolar ratio.

4. The method for preparing a high-entropy carbide coating by thermal spraying combined with methane carbonization according to claim 1, characterized in that, The particle size of the phenolic resin powder is 80~95μm.

5. The method for preparing a high-entropy carbide coating by thermal spraying combined with methane carbonization according to claim 1, characterized in that, Weigh high-entropy alloy powder and phenolic resin powder in a ratio of (7:3) to (9:1) using an electronic balance, pour them into a V-type vacuum mixer, seal it, and evacuate it to 0.08MPa to 0.1MPa. Set the speed to 30 to 60 rpm and the mixing time to 360 to 480 minutes to start mixing. After the mixing is completed, release the gas and open the equipment to obtain the mixed powder.

6. The method for preparing a high-entropy carbide coating by thermal spraying combined with methane carbonization according to claim 1, characterized in that, Thermal spraying was performed using atmospheric plasma spraying equipment. The parameters were set as follows: argon flow rate 30~50L / min, spray current 100~200A, voltage 60~120V, powder feed rate 10~30g / min, spray gun moving speed 100~200mm / s, and spraying distance 100~150mm. The mixed powder was heated to a molten or semi-molten state and sprayed onto the substrate surface to form a coating. Finally, the coating was kept at 800℃ for 2 hours in an argon atmosphere to optimize the coating performance.

7. The method for preparing a high-entropy carbide coating by thermal spraying combined with methane carbonization according to claim 1, characterized in that, The particle size difference between the phenolic resin powder and the high-entropy alloy powder is ≤5μm.

8. The method for preparing a high-entropy carbide coating by thermal spraying combined with methane carbonization according to claim 1, characterized in that, In in-situ carbonization, the porous structure inside the coating buffers 20% to 25% of the volume expansion during the carbonization reaction.

9. A method for preparing a high-entropy carbide coating by thermal spraying combined with methane carbonization, characterized in that, It is prepared by the method for preparing high-entropy carbide ceramic coatings according to any one of claims 1 to 8.

10. The high-entropy carbide ceramic coating according to claim 9, characterized in that, The porosity of the high-entropy carbide ceramic coating is ≤3%. The high-entropy carbide ceramic coating includes high-entropy carbide MC, wherein M is a combination of at least five or more elements selected from Ti, Zr, Hf, Ta, Nb, and Mo, and there is no oxide phase on the surface and inside of the coating.

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