A high-entropy carbide single-phase solid solution coating with resistance to 3000℃ high temperature and near-zero ablation, its preparation method and application

Abstract

This invention discloses a high-entropy carbide single-phase solid solution coating with near-zero ablation resistance at 3000℃, its preparation method, and its application. It primarily addresses the problem of insufficient solid solution between transition metal carbides and unsatisfactory material properties in existing coatings. The process includes: using a high-entropy carbide (TMC) mixed powder as raw material; ball milling the raw material to obtain a slurry; spray granulation to obtain TMC agglomerated powder; sintering and solidifying the powder using a graphite mold via spark plasma sintering; and finally, vacuum plasma spraying to deposit the coating onto the substrate surface, resulting in a sheet-like high-entropy carbide single-phase solid solution coating with porous and cracked structures. After oxyacetylene ablation, low-melting-point oxides are generated, forming a dense glassy ablation layer on the coating surface, achieving near-zero ablation. This invention can obtain an ideal single-phase solid solution coating with near-zero ablation characteristics at high temperatures while effectively reducing process complexity and economic costs.

Description

Technical Field

[0001] This invention belongs to the field of material surface coating technology, and further relates to high-entropy carbide single-phase solid solution coating technology. Specifically, it is a high-entropy carbide single-phase solid solution coating with high temperature resistance of 3000℃ and near-zero ablation and its preparation method, which can be used to protect carbon-based composite materials in high-temperature and oxygen-containing environments. Background Technology

[0002] The extreme high temperature, high dynamic pressure, and oxygen-rich environment of near-space hypersonic vehicles places extremely high demands on thermal protection materials. C / C composites are lightweight and possess excellent mechanical properties, especially at high temperatures, making them widely used in components for aero engines and spacecraft. However, carbon / carbon composites are easily oxidized at oxygen-rich temperatures, and the matrix material is rapidly consumed under the scouring of high-temperature gases. Current operating temperatures are generally below 1650℃, significantly limiting the application of C / C composites in hypersonic vehicles. Transition metal carbide ultra-high temperature ceramics possess advantages such as high melting point, high thermal conductivity, high strength, high hardness, and high modulus, making them promising candidates for use in hot-end structural components such as nose cones and wing leading edges of reusable aircraft. However, two major technical challenges currently hinder the application of transition metal carbides: firstly, the high temperature (3000℃) and oxygen-rich operating environment of near-space places extremely stringent requirements on the ablation resistance of transition metal carbide coating materials, which single-component transition metal carbide materials are insufficient to meet. Secondly, the preparation technology of transition metal carbide ceramic coatings with high density and ideal single-phase solid solution structure is crucial. The strong covalent bonds and low self-diffusion coefficient of ultra-high temperature transition metal carbides make it difficult to achieve sufficient and uniform solid solution of multi-component carbides in actual preparation. Therefore, the preparation of multi-component transition metal carbide single-phase solid solution coatings with resistance to 3000℃ and near-zero ablation has become one of the most critical factors for their application.

[0003] In academia and industry, chemical vapor deposition (CVD), magnetron sputtering, supersonic plasma spraying, and vacuum plasma spraying are the main methods used to prepare transition metal carbide thermal protective coatings. Currently, the transition metal carbide coatings studied mainly include four types: monocomponent, bicomponent, ternary, and high-entropy carbides. Monocomponent transition metal carbides mainly include HfC, TaC, and ZrC. Bicomponent transition metal carbides mainly include Hf-Ta-C, Hf-Zr-C, and Ta-Zr-C. Multicomponent transition metal carbide materials mainly include (Hf-Ta-W)C, (Hf-Ta-Zr)C, (Hf-Zr-Ti)C, and high-entropy carbides such as (Hf-Ta-Zr-Nb)C and (Hf-Ti-Zr-Ta-Nb)C.

[0004] The paper "Reactive plasma spray of supersaturated tungsten super-hard Ta-Hf-WC solid solution coating" by Tan ZY, Luo C, Zhu W, Yang L, Zhou YC, and Wu Q, 2021, 41:6772-6777, proposes a method combining plasma spheroidization and vacuum plasma spraying to prepare Ta-Hf-WC solid solution coatings. Although this method achieves partial solid solution of the mixed powder and improves the flowability of the powder to a certain extent, the complex and high-speed dynamic process of plasma spheroidization involves the interaction between powder particles and plasma jets. This results in insufficient solid solution between carbides during the formation of the solid solution powder, and the microstructure such as particulate phase, density, and particle size is extremely non-uniform, making it difficult to obtain an ideal single-phase Ta-Hf-WC solid solution coating. In addition, plasma spheroidization equipment is expensive, resulting in high economic costs. BCSchulz, B.Wang, RAMorris, D.Butts, GBThompson. Influence of hafnium carbide on vacuum plasma spray processed tantalum carbide microstructures[J]. Journal of the European Ceramic Society, 2013, 33: 1219-1224. A method for preparing Hf-Ta-C ternary solid solution coatings using vacuum plasma spraying was proposed. This method effectively avoids oxidation of the sprayed material by reducing the O2 content in the spraying environment, and to a certain extent achieves solid solution of TaC and HfC. Furthermore, this method has high temperature and fast deposition rate, making it suitable for the industrial mass production of ultra-high temperature thermal protective coatings. However, due to the short reaction time and high speed of the vacuum plasma spraying process, coupled with the strong covalent bonds and low diffusion coefficient of TaC and HfC, the solid solution between TaC and HfC is not sufficient, and a certain amount of Ta2C and Ta4C3 second phases actually exist in the coating.Y.Wang, B.Zhang, C.Zhang, J.Yin, MJReece. Ablation behavior of (Hf-Ta-Zr-Nb)C high entropy carbide ceramic at temperatures above 2100℃[J]. Journal of Materials Science & Technology, 2022, 113:40-47. While (Hf-Ta-Zr-Nb)C high-entropy alloy ceramics prepared by spark plasma sintering or hot pressing can yield single-phase solid solution ceramics, the research focus is primarily on high-entropy bulk carbide ceramics. Due to the low fracture toughness, poor impact resistance, and difficulty in withstanding complex thermal gradients and stresses, bulk ceramic materials are difficult to apply as thermal protection materials. Furthermore, (Hf-Ta-Zr-Nb)C high-entropy ceramics exhibit poor ablation performance; at a surface temperature of 2100℃, after 60 s of ablation, the linear ablation rate reaches as high as 8.5 μm / s.

[0005] Currently reported ultra-high temperature transition metal carbide thermal protection materials have a maximum service temperature of approximately 2600℃, which is insufficient to meet the higher requirements of service temperatures exceeding 3000℃. Existing ultra-high temperature carbide coatings mainly consist of single-component carbides such as HfC, TaC, and ZrC; binary carbides such as Hf-Ta-C, Hf-Zr-C, and Ta-Zr-C; and ternary carbide coatings such as Hf-Ta-WC and Hf-Ta-Zr-C. During high-temperature ablation, TaC and WC, due to their low oxide melting points, are prone to melting and instability during ablation, failing to protect the substrate. HfC and ZrC, due to their oxide phase transformation, undergo powder oxidation, failing to form a dense oxide layer and thus unable to protect the internal materials. Summary of the Invention

[0006] The purpose of this invention is to address the shortcomings of existing technologies by proposing a high-entropy carbide single-phase solid solution coating with near-zero ablation resistance up to 3000℃ and its preparation method. This solves the problem of insufficient solid solution between transition metal carbides in the preparation of existing high-entropy transition metal carbide coatings, which fails to obtain an ideal single-phase carbide solid solution coating. This invention employs a high-entropy transition metal carbide coating with four or more components, forming a double-layer structure of a dense glassy surface layer and an ultra-high temperature ceramic mixed-phase intermediate layer during the high-temperature ablation process. This effectively suppresses oxygen diffusion, thereby achieving near-zero ablation of the coating. The high-entropy carbide coating is prepared using a combination of spark plasma sintering and vacuum plasma spraying, which not only has low preparation cost and high efficiency but also ensures complete solid solution between transition metal carbides under the dual sintering process of spark plasma sintering and vacuum plasma spraying, realizing the preparation of a single-phase high-entropy transition metal carbide solid solution coating.

[0007] To achieve the above objectives, this invention proposes a high-entropy single-phase solid solution coating of carbide that can withstand high temperatures of 3000℃ and near-zero ablation. The coating is a high-entropy single-phase solid solution coating of carbide obtained by a vacuum plasma spraying process assisted by a spark plasma sintering process. The coating has a single-phase solid solution carbide structure and high-entropy characteristics.

[0008] The coating uses high-entropy carbide (TMC) mixed powder, deionized water, alcohol, and 2 wt.% PVA solution as raw materials; wherein the TMC mixed powder includes TaC, HfC, ZrC, WC, TiC, and NbC; and the proportion of TaC in the powder is not less than 40 at, HfC not less than 20 at, ZrC not less than 20 at, and WC+TiC+NbC not more than 20 at.

[0009] Furthermore, the coating thickness is 300-400 μm; the particle size of the TMC mixed powder in the raw material is ≤5 μm, and the purity is ≥99.9%;

[0010] Meanwhile, a method for preparing a high-entropy, near-zero ablation high-entropy carbide single-phase solid solution coating resistant to 3000℃ high temperature is proposed, including the following steps:

[0011] (1) Preparation of TMC agglomerated powder by spray granulation:

[0012] (1.1) HfC, TaC, WC, TiC, ZrC and NbC were used as raw materials, and their proportions were set as follows: TaC not less than 40 at%, HfC not less than 20 at%, ZrC not less than 20 at%, WC+TiC+NbC not more than 20 at%. The raw materials were ball-milled and dried to obtain multi-element high-entropy carbide TMC mixed powder.

[0013] (1.2) TMC mixed powder is ball-milled with deionized water, alcohol and 2wt.% PVA solution in a ratio of 4:4:1:1 to make it fully mixed and obtain a slurry for spray granulation;

[0014] (1.3) The slurry is injected into the spray tower of the spray granulation equipment, and the parameters are set for spray granulation to obtain TMC agglomerated powder;

[0015] (2) Preparation of TMC solid solution powder by spark plasma sintering:

[0016] The obtained TMC agglomerated powder was placed into a graphite mold in a spark plasma sintering furnace for sintering and solution treatment to obtain TMC solution powder.

[0017] (3) Preparation of TMC single-phase solid solution coating by vacuum plasma spraying:

[0018] (3.1) Select a substrate material and perform sandblasting on the surface of the substrate material using a sandblasting machine to obtain the treated substrate sample;

[0019] (3.2) The substrate sample is heated using a spray gun, and then TMC solid solution powder is sprayed and deposited on the surface of the substrate sample using a vacuum plasma spraying process. Ar is used as the main gas and carrier gas, and H2 is used as the auxiliary gas during the spraying process. The spraying parameters are set according to actual needs to obtain a TMC single-phase solid solution coating on the surface of the substrate sample.

[0020] In addition, the application of a high-entropy, near-zero ablation high-entropy carbide single-phase solid solution coating resistant to 3000℃ high temperature was proposed: at 6MW / m 2 and 8MW / m 2 The coating is subjected to oxyacetylene ablation at a thermal flux density. After oxyacetylene ablation, the coating generates a low-melting-point oxide, which forms a dense glassy ablation layer on its surface, achieving near-zero ablation characteristics of the coating.

[0021] Compared with the prior art, the present invention has the following advantages:

[0022] First, this invention utilizes a single-phase solid solution of multi-component high-entropy carbides as an ultra-high temperature ablation-resistant coating. This coating is prepared from multiple carbides, possesses an ultra-high melting point, and during the ablation process, through the formation of a transition metal oxide glass phase surface layer, the combined effect with the ultra-high temperature ceramic mixed-phase intermediate layer effectively reduces surface pores and channels, and inhibits oxygen diffusion. Compared with currently used carbon-based thermal protection coatings such as C / C and C / SiC, this multi-component high-entropy carbide single-phase solid solution coating has a higher service temperature, and compared with monocomponent, binary, and ternary ultra-high temperature coatings, it has excellent anti-oxidation and ablation performance, enabling near-zero ablation of the coating.

[0023] Secondly, the method for preparing multi-element high-entropy carbide single-phase solid solutions proposed in this invention, which combines spark plasma sintering and vacuum plasma spraying, is more effective than the single vacuum plasma spraying method in that the solid solution between carbides is more complete, the element distribution is more uniform, and the preparation process is simple and easy to operate. It can obtain an ideal single-phase solid solution coating while effectively reducing process complexity and economic costs. Attached Figure Description

[0024] Figure 1 This is a process flow diagram for preparing the high-entropy carbide TMC single-phase solid solution coating in this invention;

[0025] Figure 2 This is an X-ray diffraction pattern of the TMC solid solution powder after spark plasma sintering treatment in this invention.

[0026] Figure 3This is a scanning electron microscope image of the TMC solid solution powder after spark plasma sintering treatment in this invention.

[0027] Figure 4 This is a scanning electron microscope image of the cross-section of the vacuum plasma sprayed TMC single-phase solid solution coating in this invention;

[0028] Figure 5 This is a transmission electron microscope image of the vacuum plasma sprayed TMC single-phase solid solution coating in this invention;

[0029] Figure 6 This is a scanning electron microscope image of the cross-section of the TMC single-phase solid solution coating after ablation and a diagram of the ablation mechanism in this invention. Detailed Implementation

[0030] The present invention will now be further described with reference to the accompanying drawings.

[0031] Example 1: Refer to Appendix Figure 1 and 6 This invention proposes a high-entropy carbide single-phase solid solution coating with near-zero ablation resistance up to 3000℃, obtained using a discharge plasma sintering process assisted by vacuum plasma spraying. The coating is a single-phase solid solution carbide structure with high-entropy characteristics. The raw materials used are a high-entropy carbide TMC mixed powder, deionized water, alcohol, and 2 wt.% PVA solution. The TMC mixed powder includes TaC, HfC, ZrC, WC, TiC, and NbC; and the proportions of TaC, HfC, ZrC, and WC+TiC+NbC in the powder are not less than 40 at%, HfC not less than 20 at%, ZrC not less than 20 at%, and WC+TiC+NbC not more than 20 at%. In this embodiment, the preferred coating thickness is 300-400 μm, and the preferred particle size of the TMC mixed powder in the raw materials is ≤5 μm with a purity ≥99.9%.

[0032] Example 2: Refer to Appendix Figure 1 The method for preparing the high-entropy carbide single-phase solid solution coating described in Example 1 of this invention specifically includes the following steps:

[0033] Step 1. Preparation of TMC agglomerated powder by spray granulation:

[0034] (1.1) HfC, TaC, WC, TiC, ZrC and NbC were used as raw materials, and their proportions were set as follows: TaC not less than 40 at%, HfC not less than 20 at%, ZrC not less than 20 at%, WC+TiC+NbC not more than 20 at%. The raw materials were ball-milled and dried to obtain multi-element high-entropy carbide TMC mixed powder.

[0035] (1.2) TMC mixed powder is ball-milled with deionized water, alcohol and 2wt.% PVA solution in a ratio of 4:4:1:1 to make it fully mixed and obtain a slurry for spray granulation;

[0036] (1.3) The slurry is injected into the spray tower of the spray granulation equipment, and the parameters are set for spray granulation to obtain TMC agglomerated powder. This embodiment specifically completes the granulation process according to the following steps:

[0037] (1.3.1) Preheat the spray granulation equipment;

[0038] (1.3.2) The slurry is injected into the spray tower of the spray granulation equipment, the parameters are set for spray granulation, and the granulated powder is obtained in the collection tank of the equipment;

[0039] (1.3.3) The granulated powder is placed in an oven for drying to obtain TMC agglomerated powder;

[0040] Step 2. Preparation of TMC solid solution powder by spark plasma sintering:

[0041] The obtained TMC agglomerated powder was placed into a graphite mold in a spark plasma sintering furnace for sintering and solution treatment to obtain TMC solution powder.

[0042] Step 3. Preparation of TMC single-phase solid solution coating by vacuum plasma spraying:

[0043] (3.1) Select a substrate material and use a sandblasting machine to sandblast the surface of the substrate material to obtain a processed substrate sample; specifically: first, pre-treat the surface of the selected substrate material to obtain a smooth substrate, and then use a sandblasting machine to sandblast the pre-treated substrate surface.

[0044] (3.2) The substrate sample is heated using a spray gun, and then TMC solid solution powder is sprayed and deposited on the surface of the substrate sample using a vacuum plasma spraying process. Ar is used as the main gas and carrier gas, and H2 is used as the auxiliary gas during the spraying process. The spraying parameters are set according to actual needs to obtain a TMC single-phase solid solution coating on the surface of the substrate sample.

[0045] Example 3: Refer to Appendix Figure 1-4 The overall implementation steps of this embodiment are the same as those of Embodiment 2. The implementation process of the preparation method of the present invention will be further described in detail with the parameter settings given below:

[0046] The first step involves ball-milling and drying a mixture of multi-element high-entropy carbides (TMC = HfC, TaC, WC, TiC, ZrC, NbC) powder with deionized water, alcohol, and 2 wt.% PVA solution in a ratio of 4:4:1:1 until homogeneous. In this embodiment, a planetary ball mill is used for both the ball milling and drying process, with the mill speed set at 200-300 rpm and the milling time at 4-6 hours, to obtain a fully mixed slurry suitable for spray granulation.

[0047] The second step involves spray granulation within 10 minutes of thorough mixing of the slurry to prevent secondary sedimentation and stratification. During granulation, the slurry must be continuously agitated, and preheating should be initiated in advance according to the heating time of the spray granulation equipment. The parameter settings for the spray granulation equipment throughout the process include: injecting the slurry into the spray tower of the spray granulation equipment, setting the spray tower inlet temperature to 330℃~350℃, the spray tower outlet temperature to 100℃~150℃, the slurry pump speed to 14~25rpm, and the spray head rotation speed to 30-40Hz for spray granulation; finally, placing the collected granulated powder into an oven, setting the drying temperature to 80-120℃ and the drying time to 10-15h according to the amount of granulated powder; in this embodiment, drying at 100℃ for 12h is preferred to obtain TMC agglomerated powder.

[0048] The third step involves placing the obtained TMC agglomerated powder into a spark plasma sintering (SPS) mold. The sintering conditions are set as follows: sintering temperature 1900–2100℃, heating rate 50–100℃ / min, holding time 5–20 min, and chamber vacuum degree (5.4 ± 0.4) × 10⁻⁶. -1 Pa. Sintering and solution treatment are performed. Since spark plasma sintering is a process that directly applies pulsed current between powder particles for heating and sintering, it features short sintering time, rapid heating rate, and controllable microstructure. (See attached...) Figure 2 and 3 It can be seen that using spark plasma sintering to pretreat the mixed powder not only achieves complete solid solution of the multi-component carbide powder, but also provides powder with good density, spherical particles and uniform composition, providing the prerequisite for obtaining a single-phase solid solution coating with uniform microstructure.

[0049] The fourth step involves selecting tungsten metal, C / SiC composite material, or ultra-high temperature alloy as the substrate material, and performing pretreatment operations on its surface, including grinding, chamfering, polishing, and ultrasonic cleaning, to obtain a substrate material with a smooth surface. Then, the surface of the pretreated substrate material is sandblasted using a sandblasting machine. During the treatment, the sandblasting machine parameters are set as follows: sandblasting pressure 4-6 MPa, abrasive particle size less than 100 μm, and sandblasting interval 4-8 s. A substrate sample is then obtained after the treatment.

[0050] In this embodiment, tungsten metal is preferably used as the substrate material in this step and its surface is pretreated to obtain a tungsten substrate material (W substrate) with a mirror-like and smooth surface. Then, the material is sandblasted to increase the roughness of the substrate surface, remove the residual stress layer introduced by polishing, and thus enhance the adhesion between the substrate and the coating.

[0051] The fifth step involves depositing a TMC single-phase solid solution coating on the W substrate using vacuum plasma spraying. To prevent thermal stress mismatch, the substrate is preheated with a spray gun before spraying. In this embodiment, the spraying parameters for the vacuum plasma spraying process in this step are set as follows: equipment current 700A, equipment voltage 72V, gun feed rate 500m / s, powder feed rate 15-25g / min, main gas Ar flow rate 30-40L / min, auxiliary gas H2 flow rate 10-20L / min, carrier gas Ar flow rate 2-5L / min, spraying distance 150-250mm, and chamber pressure 800MPa. In this embodiment, a TMC single-phase solid solution coating with a thickness of approximately 300μm is preferably sprayed, resulting in a lamellar structure containing pores and cracks.

[0052] Reference Figure 4 The SEM image of the cross-section of the vacuum plasma-sprayed TMC single-phase solid solution coating in this invention shows that the coating obtained by this invention has good bonding with the substrate interface, and the coating exhibits a typical plasma-sprayed coating structure with flakes, pores, and microcracks. (Refer to...) Figure 5 The TEM image of the vacuum plasma-sprayed TMC single-phase solid solution coating in this invention shows that only one set of diffraction spots was found in the coating, corresponding to the face-centered cubic (FCC) structure, indicating that the carbides have achieved complete solid solution, thus obtaining a single-phase high-entropy carbide solid solution coating.

[0053] Example 4: The overall implementation steps of this example are the same as those of Examples 2 and 3. Now, specific parameters are set, and the implementation process of the present invention is further described in the form of examples:

[0054] Step A. Preparation of slurry for spray granulation:

[0055] (a1) Using HfC, TaC, WC, TiC, ZrC and NbC in a ratio of 8:4:4:2:2:1at% as raw materials, a planetary ball mill was used to dry the materials by setting the ball mill speed to 280 rpm and the ball milling time to 6 h to obtain a multi-element high-entropy carbide TMC mixed powder.

[0056] (a2) The TMC mixed powder was mixed with deionized water, alcohol and 2wt.% PVA solution in a ratio of 4:4:1:1 and then ball-milled until homogeneous. The ball mill speed was set to 280 rpm and the ball milling time was 5 h to obtain a slurry for spray granulation after thorough mixing.

[0057] Step B. Preparation of TMC agglomerate powder:

[0058] (b1) Preheat the spray granulation equipment;

[0059] (b2) Within 10 minutes after the slurry is fully mixed, the slurry is injected into the spray tower of the spray granulation equipment. The spray tower inlet temperature is set to 340°C, the spray tower outlet temperature to 120°C, the slurry pump speed to 17 rpm, and the spray head speed to 37 Hz. Spray granulation is carried out. The slurry is continuously stirred during the granulation process, and granulated powder is obtained in the collection tank of the equipment.

[0060] (b3) Place the collected granulated powder into an oven, set the drying temperature to 100℃ and the time to 12h, and obtain TMC agglomerate powder.

[0061] Step C. Place the obtained TMC agglomerated powder into a spark plasma sintering graphite mold, and set the sintering temperature to 2000℃, the heating rate to 100℃ / min, the holding time to 20min, and the chamber vacuum degree to (5.4±0.4)×10. -1 Sintering and solution treatment were performed to obtain TMC solution powder.

[0062] Step D. Select tungsten W as the substrate material and pretreat its surface. Then set the sandblasting pressure to MPa, the sand particle size to 10-100μm, and the sandblasting interval to 6s. Sandblast the surface of the substrate using a sandblasting machine to obtain the treated W substrate sample.

[0063] Step E. Heat the W substrate sample using a spray gun, and then deposit a TMC single-phase solid solution coating on its surface using a vacuum plasma spraying method. Set the spraying equipment to 700A current, 72V voltage, 500m / s gun speed, 20g / min powder feed rate, 38L / min main gas Ar flow rate, 12L / min auxiliary gas H2 flow rate, 3L / min carrier gas Ar flow rate, 200mm spraying distance, and 800MPa chamber pressure. The resulting TMC single-phase solid solution coating with a thickness of 350μm is deposited on the surface of the substrate sample.

[0064] Example 5: Refer to Appendix Figure 5 and 6This embodiment provides an application of a high-entropy carbide single-phase solid solution coating with near-zero ablation resistance at 3000℃. The high-temperature resistance and near-zero ablation performance of the TMC single-phase solid solution coating are demonstrated in its specific application. This embodiment further describes the characteristics of the high-entropy carbide single-phase solid solution coating with near-zero ablation resistance at 3000℃ by applying the TMC single-phase solid solution coating material prepared by this invention to a high-temperature ablation environment, as detailed below:

[0065] A high-temperature flame is generated by the combustion of a mixture of oxygen and acetylene gases. This flame is then directly directed at the high-entropy carbide single-phase solid solution coating material prepared according to this invention, at a speed of 6 MW / m². 2 and 8MW / m 2 The coating is subjected to oxyacetylene ablation at a thermal flux density. After oxyacetylene ablation, the coating generates a low-melting-point oxide, forming a dense glassy ablation layer on its surface, achieving near-zero ablation characteristics. In this embodiment, the equipment for simulating the high-temperature ablation environment is simple, low-cost, and easy to operate, enabling rapid measurement of the ablation status of the coating under high-temperature conditions. In the specific application of this embodiment, the ablation parameters are set as follows: oxyacetylene flame nozzle diameter 5mm, oxygen pressure 0.45MPa, flow rate 12L / min, acetylene pressure 0.095MPa, flow rate 6-8L / min, distance between the oxyacetylene nozzle and the coating sample 10mm, and ablation time 120s.

[0066] See attached document Figure 6 The SEM images of the cross-section of the TMC single-phase solid solution coating and the ablation mechanism diagram after ablation in this invention show that after the coating is ablated by oxyacetylene, a dense glassy ablation layer is formed on the coating surface due to the generation of low-melting-point oxides, which effectively prevents oxygen diffusion, thereby achieving near-zero ablation characteristics of the coating. Its linear ablation rate is less than 0.2 μm / s, which provides a favorable guarantee for the application of this coating in hypersonic vehicles.

[0067] The technical problem this invention aims to solve is the difficulty in preparing high-entropy carbide single-phase solid solution coatings, which are expected to meet the critical requirement of 3000℃ thermal protection in aerospace applications. This invention primarily utilizes a combination of spark plasma sintering and vacuum plasma spraying to prepare high-entropy carbide solid solution coatings that withstand 3000℃ temperatures, exhibit near-zero ablation, and possess ideal single-phase solid solution characteristics. Addressing the issues of strong covalent bonds and low self-diffusion coefficients in ultra-high temperature carbide ceramics, this invention employs a combination of spark plasma sintering and vacuum plasma spraying to prepare the high-entropy carbide coating. The spark plasma sintering pretreatment of the mixed powder not only achieves complete solid solution of the multi-component carbide powder but also provides powder with good density, spherical particles, and uniform composition, providing the prerequisites for obtaining a single-phase solid solution coating with a uniform microstructure. To address the poor high-temperature ablation behavior of single-component carbide ceramics, which makes them unsuitable for applications in ultra-high temperature extreme environments, this invention innovatively prepares a single-phase solid solution high-entropy carbide coating from various carbides such as HfC, TaC, ZrC, NbC, and WC. This coating not only has a high melting point exceeding 3000℃, but also effectively suppresses oxygen diffusion during ablation by generating a transition metal oxide glass phase surface layer and an ultra-high temperature ceramic mixed-phase intermediate layer, thereby achieving near-zero ablation of the coating.

[0068] The parts of this invention not described in detail are common knowledge to those skilled in the art.

[0069] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Obviously, those skilled in the art, after understanding the content and principle of the present invention, may make various modifications and changes in form and detail without departing from the principle and structure of the present invention. However, these modifications and changes based on the concept of the present invention are still within the scope of protection of the claims of the present invention.

Claims

1. A high-entropy, near-zero ablation high-entropy carbide single-phase solid solution coating resistant to 3000℃ high temperature, characterized in that: The coating is a high-entropy carbide single-phase solid solution coating obtained by a vacuum plasma spraying process assisted by a spark plasma sintering process. The coating has a single-phase solid solution carbide structure and high-entropy characteristics. The coating uses high-entropy carbide (TMC) mixed powder, deionized water, alcohol, and 2 wt.% PVA solution as raw materials; wherein the TMC mixed powder includes TaC, HfC, ZrC, WC, TiC, and NbC; and the proportion of TaC in the powder is not less than 40 at%, HfC not less than 20 at%, ZrC not less than 20 at%, and WC+TiC+NbC not more than 20 at%.

2. The coating according to claim 1, characterized in that: The coating thickness is 300-400 μm; the particle size of the TMC mixed powder in the raw material is ≤5 μm and the purity is ≥99.9%.

3. A method for preparing a high-entropy, near-zero ablation-resistant, high-entropy carbide single-phase solid solution coating resistant to 3000℃ high temperature, characterized in that, Includes the following steps: (1) Preparation of TMC agglomerated powder by spray granulation: (1.1) Using HfC, TaC, WC, TiC, ZrC and NbC as raw materials, and setting their proportions as follows: TaC not less than 40 at%, HfC not less than 20 at%, ZrC not less than 20 at%, WC+TiC+NbC not more than 20 at%, and ball milling and drying them to obtain multi-element high-entropy carbide TMC mixed powder; (1.2) TMC mixed powder is ball-milled with deionized water, alcohol and 2 wt.% PVA solution in a ratio of 4:4:1:1 to make it fully mixed and obtain a slurry for spray granulation; (1.3) Inject the slurry into the spray tower of the spray granulation equipment, set the parameters for spray granulation, and obtain TMC agglomerated powder; (2) Preparation of TMC solid solution powder by spark plasma sintering: The obtained TMC agglomerated powder was placed into a graphite mold in a spark plasma sintering furnace for sintering and solution treatment to obtain TMC solution powder. (3) Preparation of TMC single-phase solid solution coating by vacuum plasma spraying: (3.1) Select a substrate material and perform sandblasting on the surface of the substrate material using a sandblasting machine to obtain the treated substrate sample; (3.2) The substrate sample is heated by a spray gun, and then TMC solid solution powder is sprayed and deposited on the surface of the substrate sample by vacuum plasma spraying process. Ar is used as the main gas and carrier gas and H2 is used as the auxiliary gas during the spraying process. The spraying parameters are set according to actual needs to obtain a TMC single-phase solid solution coating on the surface of the substrate sample.

4. The method according to claim 3, characterized in that: The ball mill is a planetary ball mill with a set rotation speed of 200-300 rpm and a milling time of 4-6 hours.

5. The method according to claim 3, characterized in that: The parameters set in step (1.3) include: spray tower inlet temperature 330 ℃~350 ℃, spray tower outlet temperature 100 ℃~150 ℃, slurry pump speed 14~25 rpm, and spray head rotation speed 30-40Hz.

6. The method according to claim 3, characterized in that: The sintering and solution treatment in step (2) is performed under the following conditions: sintering temperature 1900~2100 ℃, heating rate 50~100 ℃ / min, holding time 5~20 min, and chamber vacuum degree (5.4±0.4)×10 -1 Pa.

7. The method according to claim 3, characterized in that: The substrate material mentioned in step (3.1) is tungsten metal, C / SiC composite material or ultra-high temperature alloy; the sandblasting treatment is set under the following conditions: sandblasting pressure between 4-6 MPa, sand particle size less than 100 μm, and sandblasting interval time of 4-8 s.

8. The method according to claim 3, characterized in that: The spraying parameters set in step (3.2) include: equipment current 700 A, equipment voltage 72 V, gun speed 500 m / s, powder feeding rate 15~25 g / min, main gas Ar flow rate 30~40 L / min, auxiliary gas H2 flow rate 10~20 L / min, carrier gas Ar flow rate 2~5 L / min, spraying distance 150~250 mm, and chamber pressure 800 MPa.

9. An application of the coating according to claim 1, characterized in that: The coating has applications in the field of thermal protection, including at 6 MW / m 2 and 8 MW / m 2 The coating is subjected to oxyacetylene ablation at a thermal flux density to generate a low-melting-point oxide, which forms a dense glassy ablation layer on its surface; the coating has near-zero ablation characteristics.

10. The application according to claim 9, characterized in that: The coating was subjected to oxyacetylene ablation, with the following ablation parameters: oxyacetylene flame nozzle diameter 5 mm, oxygen pressure 0.45 MPa and flow rate 12 L / min, acetylene pressure 0.095 MPa and flow rate 6 ~ 8 L / min, distance between the oxyacetylene nozzle and the coating sample 10 mm, and ablation time 120 s.

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