A method for preparing high-entropy carbide ablation-resistant coatings using reduced oxides

Abstract

This invention discloses a method for preparing a high-entropy carbide ablation-resistant coating by reducing oxides. The chemical phase of the high-entropy carbide ablation-resistant coating is represented as (Ti Zr Hf Ta M)C, where M is Nb, Mo, W or V. The high-entropy carbide ablation-resistant coating has excellent mechanical properties and ablation resistance. It can be prepared simply by mixing metal oxide powder and carbon material powder, ball milling, and then sintering. The preparation method is very simple.

Description

Technical Field

[0001] This invention belongs to the field of high-entropy carbide ablation-resistant coating technology, and relates to a method for preparing high-entropy carbide ablation-resistant coatings by reducing oxides. Background Technology

[0002] Solid rocket engine combustion chambers, scramjet engine combustion chambers, and the surfaces of hypersonic vehicles all face extremely high-temperature service environments. To improve service life and reduce usage limitations, protective coatings are needed for the surfaces of hot-end materials. When a vehicle reaches Mach 7, its surface temperature exceeds 2500 K; when it exceeds Mach 10, the surface temperature reaches 3889 K, far exceeding the heat resistance temperatures of traditional high-temperature structural materials such as nickel alloys, refractory alloys, and SiC / SiC ceramic composites. High-entropy carbides possess characteristics such as high hardness, high strength, high wear resistance, high mechanical properties, and low thermal conductivity, making them a promising candidate for protective coatings on hot-end material surfaces. However, the current performance of high-entropy carbides does not meet the requirements of aircraft.

[0003] For the reasons mentioned above, there is an urgent need to study a high-entropy carbide ablation coating with excellent performance. Summary of the Invention

[0004] To overcome the above problems, the inventors conducted intensive research and developed a method for preparing a high-entropy carbide ablation-resistant coating by reducing oxides. The chemical phase of the high-entropy carbide ablation-resistant coating is represented as (Ti Zr Hf Ta M)C, where M is Nb, Mo, W, or V. The high-entropy carbide ablation-resistant coating has excellent mechanical properties and ablation resistance. It can be prepared simply by mixing and ball-milling metal oxide powder with carbon material powder, followed by sintering. The preparation method is very simple, thus completing this invention.

[0005] Specifically, the object of the present invention is to provide the following aspects:

[0006] On the one hand, a high-entropy carbide ablation-resistant coating is provided, wherein the chemical phase of the high-entropy carbide ablation-resistant coating is represented as: (Ti Zr Hf Ta M)C, where M is Nb, Mo, W or V.

[0007] The high-entropy carbide ablation-resistant coating has a single-phase solid solution structure.

[0008] The nanoindentation hardness of the high-entropy carbide anti-ablation coating is 59.9–60.7 GPa.

[0009] Secondly, a method for preparing a high-entropy carbide ablation-resistant coating is provided, the method comprising:

[0010] Step 1: Mix the metal oxide powder and carbon material powder and ball mill them to obtain a mixed powder;

[0011] Step 2: Sinter the mixed powder to obtain the high-entropy carbide ablation-resistant coating.

[0012] In step 1, the metal oxide powder includes HfO2, ZrO2, Ta2O5 and TiO2.

[0013] In step 1, the metal oxide powder further includes one of NbO, MoO2, WO3, and V2O5.

[0014] In step 1, the metal oxides are in an equimolar ratio.

[0015] In step 1, the carbon material is carbon black.

[0016] In step 2, the sintering includes:

[0017] First stage of sintering: The temperature is increased from room temperature to 1650℃ to 1750℃ at a heating rate of 30 to 100℃ / min, and then held for 15 to 30 minutes at a pressure of 10 to 30 MPa.

[0018] Two-stage sintering: The temperature is increased from the holding temperature of the first-stage sintering to 2000℃~2200℃ at a heating rate of 30~100℃ / min, and then held for 5~15min at a pressure of 10~30MPa.

[0019] Thirdly, an ablation-resistant coating is provided, wherein the ablation-resistant coating contains the high-entropy carbide ablation-resistant coating described in the first aspect or the high-entropy carbide ablation-resistant coating prepared according to the method described in the second aspect.

[0020] The beneficial effects of this invention include:

[0021] (1) The high-entropy carbide ablation-resistant coating provided by the present invention has high density and strong nano-indentation hardness.

[0022] (2) The method for preparing high-entropy carbide ablation-resistant coating provided by the present invention adopts staged sintering, which realizes both the carbothermic reduction reaction of metal oxides and the desired coating. The preparation cycle is short, the method is simple, and the reaction materials can be adjusted according to the actual coating requirements. It has potential applications in ablation-resistant coatings. Attached Figure Description

[0023] 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.

[0024] In the attached diagram:

[0025] Figure 1 SEM images of the mixed powders in Example 1 are shown;

[0026] Figure 2 The X-ray diffraction pattern of the mixed powder in Example 1 is shown;

[0027] Figure 3 The X-ray diffraction pattern of the high-entropy carbide ablation-resistant coating prepared in Example 1 is shown.

[0028] Figure 4 A macroscopic photograph of the high-entropy carbide ablation-resistant coating prepared in Example 1 is shown.

[0029] Figure 5 The cross-sectional micrograph of the high-entropy carbide ablation-resistant coating prepared in Example 1 is shown.

[0030] Figure 6 This shows a macroscopic photograph of the high-entropy carbide ablation-resistant coating prepared in Example 1 after ablation;

[0031] Figure 7 The X-ray diffraction pattern of the high-entropy carbide ablation-resistant coating prepared in Comparative Example 1 is shown. Detailed Implementation

[0032] The following will refer to the appendix. Figures 1 to 7 Specific embodiments of the invention will be described in more detail below. While specific embodiments of the invention are shown in the accompanying drawings, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the invention and to fully convey the scope of the invention to those skilled in the art.

[0033] 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.

[0034] In the description of this invention, it should be noted that the terms "upper," "lower," "inner," "outer," "front," and "rear," etc., indicate the orientation or positional relationship based on the orientation or positional relationship in the working state of this invention, and are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention. Furthermore, the terms "first," "second," "third," and "fourth" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0035] 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.

[0036] On one hand, according to the present invention, a high-entropy carbide ablation-resistant coating is provided, wherein the chemical phase of the high-entropy carbide ablation-resistant coating is represented as: (Ti Zr Hf Ta M)C, where M is Nb, Mo, W or V.

[0037] Of course, the high-entropy carbide anti-ablation coating may also not contain the M element. In this case, the chemical phase of the high-entropy carbide anti-ablation coating is represented as: (Ti Zr Hf Ta)C.

[0038] Furthermore, the high-entropy carbide ablation-resistant coating has a single-phase solid solution structure; the thickness of the high-entropy carbide ablation-resistant coating is 220–240 μm, and the nanoindentation hardness is 59.9–60.7 GPa.

[0039] On the other hand, according to a method for preparing a high-entropy carbide ablation-resistant coating provided by the present invention, the method includes:

[0040] Step 1: Mix the metal oxide powder and carbon material powder and ball mill them to obtain a mixed powder;

[0041] Step 2: Sinter the mixed powder to obtain the high-entropy carbide ablation-resistant coating.

[0042] Specifically:

[0043] Step 1: Mix the metal oxide powder and carbon material powder and ball mill them to obtain a mixed powder.

[0044] In step 1, the metal oxide powder includes HfO2, ZrO2, Ta2O5 and TiO2, and also includes one of NbO, MoO2, WO3 and V2O5, optionally including one of NbO, MoO2, WO3 and V2O5.

[0045] Ti possesses characteristics such as low density, excellent mechanical strength, plasticity, and good heat resistance. Zr readily forms an oxide film on its surface, exhibiting corrosion resistance. At high temperatures, it can react with non-metallic elements and many metallic elements to form solid solutions. Hf is associated with Zr, exhibiting a cubic close-packed structure below 1300℃ and a body-centered cubic structure above 1300℃, demonstrating plasticity and stability in air. Ta is highly ductile, has a very small coefficient of thermal expansion, and Ta₂O₅ remains very stable even at high temperatures, also possessing extremely high corrosion resistance. In addition to the above, the carbides of refractory metals Zr, Hf, and Ta have higher melting points, hardness, and elastic moduli than borides and nitrides. They belong to the NaCl-type face-centered cubic structure, with a wide non-stoichiometric range, which is beneficial for carbide modification. HfO₂, ZrO₂, Ta₂O₅, and TiO₂ form solid solutions with ultra-high melting points through high-temperature solid solution formation.

[0046] In step 1, the metal elements in the metal oxide are in equal molar ratios, based on the molar ratio of metal elements.

[0047] In step 1, the particle size of the metal oxides is between 1 and 8 μm.

[0048] In step 1, the carbon material is carbon black.

[0049] In step 1, the carbon material is in excess to ensure that the metal oxide powder reacts completely with the carbon element. The molar ratio of the carbon material to the metal element in the metal oxide powder is (2-3):1, preferably (2.4-2.6):1, and more preferably 2.5:1.

[0050] In step 1, as the ball milling rate increases, the ball milling efficiency naturally increases as well. At this point, the impact energy of the milling balls on the material increases. However, if the ball milling rate is too high, it will significantly weaken the collision and compression effect of the milling balls on the milled material. Preferably, the ball milling rate is 100–260 r / min; more preferably, the ball milling rate is 160–260 r / min; for example, the ball milling rate is 200 r / min.

[0051] Furthermore, the longer the ball milling time, the more intense the crushing and compressing effects of the milling jar and milling balls on the milled material, and the more energy is generated during the milling process. The milling time has varying effects on different milled materials and is closely related to factors such as the composition, size, and properties of the milled material. If the milling time is too long, the milled material will agglomerate, greatly affecting the material's performance. Preferably, the milling time is 2–12 hours; more preferably, the milling time is 6–10 hours, for example, 10 hours.

[0052] Furthermore, since the grinding balls and the grinding material require a certain amount of space for free collision, the selection of the loading amount is crucial. Increasing the number of grinding balls promotes the impact of the grinding material, which can improve the energy conversion efficiency of the grinding material and effectively shorten the grinding time; however, the filling amount of grinding balls is not always better the larger it is. When the loading amount of grinding balls is too large, the limited space inside the grinding jar restricts the effective crushing of the grinding material, resulting in a prolonged grinding time and affecting the performance of the prepared material. Preferably, the ball-to-material ratio used in the grinding is (3-8):1, more preferably, the ball-to-material ratio used in the grinding is (4-6):1, for example, the ball-to-material ratio used in the grinding is 5:1.

[0053] Step 2: Sinter the mixed powder to obtain the high-entropy carbide ablation-resistant coating.

[0054] In step 2, before sintering, it is preferable to pre-press the mixed powder to obtain a high-entropy carbide ablation-resistant coating with excellent density.

[0055] Further, the mixed powder is spread onto the carbon-based surface and then pre-pressed.

[0056] The carbon-based material is a C / C composite material or a graphite matrix, and the mass of the mixed powder is selected according to the thickness of the high-entropy carbide ablation-resistant coating.

[0057] According to the present invention, pressing can increase the adhesion and coherence of metal carbide powder. The pre-pressing pressure is 20-30 MPa, preferably 25-30 MPa, and more preferably 30 MPa.

[0058] According to the present invention, pressing metal carbide powder for a period of time can increase the density between particles. Of course, a longer pre-pressing time will not have a significant impact on the density between particles. The pre-pressing time is 10 to 30 minutes, preferably 15 to 25 minutes, and more preferably 20 minutes.

[0059] In step 2, before sintering, an inert gas such as argon or helium is introduced into the sintering apparatus to prevent impurities from affecting the reaction.

[0060] In step 2, before sintering, a vacuum of less than 6 Pa is required to prevent the mixed powder from oxidizing during the high-temperature sintering process.

[0061] In step 2, the sintering is a staged sintering process, including:

[0062] First stage of sintering: The temperature is increased from room temperature to 1650℃ to 1750℃ at a heating rate of 60 to 120℃ / min, and then held for 15 to 30 minutes at a pressure of 10 to 30 MPa.

[0063] Two-stage sintering: The temperature is increased from the holding temperature of the first-stage sintering to 2000℃~2200℃ at a heating rate of 50~100℃ / min, and then held for 5~15min at a pressure of 10~30MPa.

[0064] Preferably, the sintering is staged sintering, comprising:

[0065] First stage of sintering: The temperature is increased from room temperature to 1700-1750℃ at a heating rate of 70-110℃ / min, and held at this temperature for 15-25 minutes, while maintaining a pressure of 25-30MPa.

[0066] Two-stage sintering: The temperature is increased from the holding temperature of the first-stage sintering to 2000℃~2200℃ at a heating rate of 60~90℃ / min, and then held for 7~12min at a pressure of 25~30MPa.

[0067] More preferably, the sintering is staged sintering, including:

[0068] First stage of sintering: The temperature is increased from room temperature to 1700℃ at a heating rate of 100℃ / min, and then held at this temperature for 25 minutes at a pressure of 30MPa.

[0069] Two-stage sintering: The temperature is increased from the holding temperature of the first-stage sintering to 2000℃ at a heating rate of 70℃ / min, and then held for 10 minutes at a pressure of 30MPa.

[0070] According to the present invention, during the first stage of sintering, a carbothermic reduction reaction of metal oxides is achieved within the holding time to generate carbides; then, a high-entropy carbide ablation-resistant coating is obtained during the second stage of sintering.

[0071] Furthermore, if the heating rate during the first-stage sintering process is too low, it will lead to larger grains, but an excessively high temperature rate will cause a decrease in the density of the resulting high-entropy carbide ablation-resistant coating. If the holding temperature during the first-stage sintering is too low, the metal oxides cannot be reduced, and the resulting high-entropy carbide ablation-resistant coating will contain oxide phases, resulting in poor high-temperature performance. However, if the holding temperature during sintering is too high, it will affect the second-stage sintering temperature because it will far exceed the Gibbs free energy reaction temperature required for the carbonization of metal oxides. As the holding time during the first-stage sintering increases, the reaction between the metal oxides and carbon materials becomes more complete, but an excessively long time is unnecessary and may lead to side reactions. If the pressure during the first-stage sintering is too low, it will cause a decrease in the density of the high-entropy carbide ablation-resistant coating, while if the pressure is too high, it will cause the sintering mold to crack.

[0072] Furthermore, if the heating rate during the second-stage sintering process is too low, it will lead to a longer preparation cycle, but an excessively high temperature rate will result in insufficient reaction. If the holding temperature of the second-stage sintering is too low, it will be difficult for the carbides obtained from the first-stage sintering to form a single solid solution structure, but if the holding temperature of the sintering is too high, it will lead to overburning. As the holding time of the second-stage sintering is extended, the carbides obtained from the first-stage sintering gradually form a single solid solution structure, but an excessively long time will also lead to overburning. If the pressure of the second-stage sintering is too low, the second-stage sintering temperature will need to be further increased, and if the pressure is too high, it will cause the sintering mold to break.

[0073] In step 2, after sintering, to avoid the formation of cracks due to large internal stress during rapid cooling of the prepared sample, the temperature is lowered to 500-700°C at a cooling rate of 20-100°C / min, and then naturally cooled to room temperature; preferably, the temperature is lowered to 570-650°C at a cooling rate of 40-80°C / min, and then naturally cooled to room temperature; more preferably, the temperature is lowered to 600°C at a cooling rate of 60°C / min, and then naturally cooled to room temperature.

[0074] In step 2, the ambient temperature is generally 0 to 40°C, for example, 25°C.

[0075] In step 2, the DC pulse current is turned on during sintering. When the temperature drops to the required temperature, such as 600°C, the DC pulse current is turned off, and the temperature is then allowed to cool naturally to room temperature.

[0076] In step 2, the inert gas needs to be continuously supplied from before sintering until the sintering end temperature drops to room temperature.

[0077] In step 2, the sintering is preferably performed using spark plasma sintering, for example, in a spark plasma sintering apparatus. This method features sintering under pressure, where the plasma generated by the pulsed current and the pressure applied during sintering help lower the sintering temperature of the powder. Simultaneously, the low voltage and high current characteristics enable rapid and dense sintering of the powder.

[0078] Thirdly, according to the present invention, an ablation-resistant coating is provided, wherein the ablation-resistant coating contains the high-entropy carbide ablation-resistant coating described in the first aspect or the high-entropy carbide ablation-resistant coating prepared according to the method described in the second aspect.

[0079] Example

[0080] The present invention is further described below through specific examples; however, these examples are merely exemplary and do not constitute any limitation on the scope of protection of the present invention.

[0081] Example 1

[0082] TiO2, ZrO2, HfO2, Ta2O5, and carbon black powders in a molar ratio of 1:1:1:0.5:12.5 were mixed and placed in a ball mill jar. The total amount of TiO2, ZrO2, HfO2, Ta2O5, and carbon black powders was 15g, and the masses of TiO2, ZrO2, HfO2, Ta2O5, and carbon black powders were 2.19g, 3.38g, 5.76g, 6.03g, and 1.85g, respectively. The particle size of each powder was between 1-8μm. The mixture was ball-milled in the jar at 200r / min for 10h with a ball-to-powder weight ratio of 5:1. After ball milling, a mixed powder was obtained. The mixed powder was passed through a 200-mesh sieve and then ground uniformly using an agate mortar.

[0083] Next, a graphite substrate (model JUYI-8) with a diameter of 30 mm and a height of 10 mm was placed on a graphite mold. 2 g of mixed powder was spread onto the graphite block, and it was pre-pressed at 30 MPa for 20 min on a tablet press. At this time, the graphite mold was placed in the furnace of the spark plasma sintering system, the vacuum was drawn to 6 Pa, argon gas was introduced into the sintering system, and the DC pulse current was turned on. Sintering was carried out according to the following procedure:

[0084] First stage of sintering: The temperature is increased from room temperature to 1700℃ at a heating rate of 100℃ / min, and then held at this temperature for 25 minutes at a pressure of 30MPa.

[0085] Two-stage sintering: The temperature is increased from the holding temperature of 1700℃ in the first stage sintering to 2000℃ at a heating rate of 70℃ / min, and then held for 10 minutes at a pressure of 30MPa.

[0086] Next, the temperature was lowered to 600°C at a rate of 60°C / min. At this point, the DC pulse current was turned off, and the material was allowed to cool naturally to room temperature, thus obtaining a high-entropy carbide ablation-resistant coating.

[0087] The nanoindentation hardness of the obtained high-entropy carbide ablation-resistant coating was tested to be 60.7 GPa.

[0088] Figure 1 The microstructure of the mixed powder shown in the figure indicates that the particle size of the mixed powder is relatively uniform and there is no agglomeration. Figure 2 The X-ray diffraction pattern of the mixed powders reveals the phases of each mixed powder. Figure 3 The X-ray diffraction pattern of the prepared high-entropy carbide ablation-resistant coating shows that a single solid solution structure is formed. Figure 4 The image shows the macroscopic morphology of the prepared high-entropy carbide ablation-resistant coating, indicating that the coating is densely sintered; (Attached) Figure 5 The image shows the cross-sectional microstructure of the prepared high-entropy carbide ablation-resistant coating, revealing a coating thickness of approximately 240 μm.

[0089] The obtained high-entropy carbide ablation-resistant coating was subjected to a heat flux density of 5MW / m 2 Hydrogen-oxygen ablation for 90 s, linear ablation rate 0.06 μm / s. Figure 6 Macroscopic photographs of the high-entropy carbide anti-ablation coating after ablation are shown. It can be seen that the high-entropy carbide anti-ablation coating after ablation does not show exposed substrate surface, and the coating does not crack, exhibiting typical ablation morphology characteristics.

[0090] Example 2

[0091] TiO2, ZrO2, HfO2, Ta2O5, and carbon black powders in a molar ratio of 1:1:1:0.5:12.5 were mixed and placed in a ball mill jar. The total amount of TiO2, ZrO2, HfO2, Ta2O5, and carbon black powders was 15g, and the masses of TiO2, ZrO2, HfO2, Ta2O5, and carbon black powders were 2.19g, 3.38g, 5.76g, 6.03g, and 1.85g, respectively. The particle size of each powder was between 1-8μm. The mixture was ball-milled in the jar at 220r / min for 8h with a ball-to-powder weight ratio of 5:1. After ball milling, a mixed powder was obtained. The mixed powder was passed through a 200-mesh sieve and then ground uniformly using an agate mortar.

[0092] Next, a graphite substrate (model JUYI-8) with a diameter of 30 mm and a height of 10 mm was placed on a graphite mold. 2 g of mixed powder was spread onto the graphite block, and it was pre-pressed at 30 MPa for 20 min on a tablet press. At this time, the graphite mold was placed in the furnace of the spark plasma sintering system, the vacuum was drawn to 6 Pa, argon gas was introduced into the sintering system, and the DC pulse current was turned on. Sintering was carried out according to the following procedure:

[0093] First stage of sintering: The temperature is increased from room temperature to 1650℃ at a heating rate of 60℃ / min, and then held at this temperature for 15min, with a pressure of 25MPa.

[0094] Two-stage sintering: The temperature is increased from the holding temperature of 1650℃ in the first stage sintering to 2100℃ at a heating rate of 50℃ / min, and then held for 10 minutes at a pressure of 25MPa.

[0095] Next, the temperature was lowered to 600℃ at a rate of 40℃ / min. At this point, the DC pulse current was turned off, and the material was allowed to cool naturally to room temperature, resulting in a high-entropy carbide ablation-resistant coating with a thickness of 220μm. The nanoindentation hardness was measured to be 60.2GPa.

[0096] Example 3

[0097] TiO2, ZrO2, HfO2, Ta2O5, and carbon black powders in a molar ratio of 1:1:1:0.5:12.5 were mixed and placed in a ball mill jar. The total amount of TiO2, ZrO2, HfO2, Ta2O5, and carbon black powders was 15g, and the masses of TiO2, ZrO2, HfO2, Ta2O5, and carbon black powders were 2.19g, 3.38g, 5.76g, 6.03g, and 1.85g, respectively. The particle size of each powder was between 1-8μm. The mixture was ball-milled in the jar at 260r / min for 6h with a ball-to-powder weight ratio of 5:1. After ball milling, a mixed powder was obtained. The mixed powder was passed through a 200-mesh sieve and then ground evenly using an agate mortar.

[0098] Next, a graphite substrate (model JUYI-8) with a diameter of 30 mm and a height of 10 mm was placed on a graphite mold. 2 g of mixed powder was spread onto the graphite block, and it was pre-pressed at 30 MPa for 20 min on a tablet press. At this time, the graphite mold was placed in the furnace of the spark plasma sintering system, the vacuum was drawn to 6 Pa, argon gas was introduced into the sintering system, and the DC pulse current was turned on. Sintering was carried out according to the following procedure:

[0099] First stage of sintering: The temperature is increased from room temperature to 1750℃ at a heating rate of 110℃ / min, and then held at this temperature for 15min, with a pressure of 20MPa.

[0100] Two-stage sintering: The temperature is increased from the holding temperature of 1750℃ in the first stage sintering to 2200℃ at a heating rate of 100℃ / min, and then held for 5 minutes at a pressure of 20MPa.

[0101] Next, the temperature was lowered to 600℃ at a rate of 80℃ / min. At this point, the DC pulse current was turned off, and the material was allowed to cool naturally to room temperature, resulting in a high-entropy carbide ablation-resistant coating with a thickness of 230μm. The nanoindentation hardness was measured to be 59.9GPa.

[0102] Comparative Example

[0103] Comparative Example 1

[0104] TiO2, ZrO2, HfO2, Ta2O5, and carbon black powders in a molar ratio of 1:1:1:0.5:12.5 were mixed and placed in a ball mill jar. The total amount of TiO2, ZrO2, HfO2, Ta2O5, and carbon black powders was 15g, and the masses of TiO2, ZrO2, HfO2, Ta2O5, and carbon black powders were 2.19g, 3.38g, 5.76g, 6.03g, and 1.85g, respectively. The particle size of each powder was between 1-8μm. The mixture was ball-milled in the jar at 260r / min for 6h with a ball-to-powder weight ratio of 1:5. After ball milling, a mixed powder was obtained. The mixed powder was passed through a 200-mesh sieve and then ground evenly using an agate mortar.

[0105] Next, a graphite substrate (model JUYI-8) with a diameter of 30 mm and a height of 10 mm was placed on a graphite mold. 2 g of mixed powder was spread onto the graphite block. The substrate was pre-pressed at 30 MPa for 20 min on a tablet press. At this time, the graphite mold was placed in the furnace of the spark plasma sintering system. The vacuum was evacuated to 6 Pa. Argon gas was introduced into the sintering system. The DC pulse current was turned on and sintering was performed according to the following procedure: the temperature was increased from room temperature to 2000℃ at a heating rate of 100℃ / min. The temperature was then held for 15 min at a pressure of 30 MPa.

[0106] Next, the temperature was lowered to 600°C at a rate of 60°C / min. At this point, the DC pulse current was turned off, and the material was allowed to cool naturally to room temperature, thus obtaining a high-entropy carbide ablation-resistant coating with a thickness of 230 μm.

[0107] XRD patterns of the prepared high-entropy carbide ablation-resistant coating are as follows: Figure 7 As shown, it is evident that the high-entropy carbide ablation-resistant coating still exhibits peaks of ZrO2, HfO2, and TaO, indicating that under this sintering temperature condition, a high-entropy carbide ablation-resistant coating with a single-phase solid solution structure cannot be successfully prepared.

[0108] The obtained high-entropy carbide ablation-resistant coating was subjected to a heat flux density of 5MW / m 2 Oxyacetylene ablation for 90 s yielded a linear ablation rate of 3.25 μm / s.

[0109] The present invention has been described in detail above with reference to preferred embodiments and exemplary examples. However, it should be noted that these specific embodiments are merely illustrative explanations of the invention and do not constitute any limitation on the scope of protection of the invention. Various improvements, equivalent substitutions, or modifications can be made to the technical content and embodiments of the present invention without departing from the spirit and scope of protection of the invention, and all such modifications fall within the scope of protection of the present invention. The scope of protection of the present invention is defined by the appended claims.

Claims

1. A high-entropy carbide ablation-resistant coating, characterized in that, The chemical phase of the high-entropy carbide ablation-resistant coating is represented as: (Ti Zr Hf Ta M)C, where M is Nb, Mo, W or V; The high-entropy carbide ablation-resistant coating is prepared by the following steps: Step 1: Mix and ball-mill the metal oxide powder and carbon material powder to obtain a mixed powder; the metal oxide powder includes HfO2, ZrO2, Ta2O5 and TiO2, and also includes one of NbO, MoO2, WO3 and V2O5; the particle size of the metal oxides is between 1 and 8 μm; the molar ratio of metal elements in the carbon material and metal oxide powder is (2~3):1; Step 2: Spread the mixed powder onto the carbon-based surface, then pre-press and sinter sequentially to obtain the high-entropy carbide ablation-resistant coating; The sintering includes: First stage of sintering: The temperature is increased from room temperature to 1650°C to 1750°C at a heating rate of 30 to 100°C / min, and then held for 15 to 30 min at a pressure of 10 to 30 MPa. Two-stage sintering: The temperature is increased from the holding temperature of the first-stage sintering to 2000°C to 2200°C at a heating rate of 30~100°C / min, and then held for 5~15 min at a pressure of 10~30 MPa.

2. The high-entropy carbide ablation-resistant coating according to claim 1, characterized in that, The high-entropy carbide ablation-resistant coating has a single-phase solid solution structure.

3. The high-entropy carbide ablation-resistant coating according to claim 1, characterized in that, The nanoindentation hardness of the high-entropy carbide anti-ablation coating is 59.9~60.7 GPa.

4. The high-entropy carbide ablation-resistant coating according to claim 1, characterized in that, In step 1, the metal oxides are in an equimolar ratio.

5. The high-entropy carbide ablation-resistant coating according to claim 1, characterized in that, In step 1, the carbon material is carbon black.

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