Preparation method of composite ceramic powder for thermal spraying

Abstract

The invention discloses a preparation method of composite ceramic powder for thermal spraying, and relates to the technical field of ceramic material preparation. When the composite ceramic powder for thermal spraying is prepared, firstly, the surface of silicon carbide powder is corroded by a chemical method, secondly, high-entropy carbide is deposited on the surface of the silicon carbide powder by a magnetron sputtering method, and finally, a high-entropy oxide precursor is coated; and performing high-temperature heat treatment in a reducing atmosphere to form a cobalt-based high-entropy alloy, thereby obtaining the composite ceramic powder for thermal spraying. The unique core-shell structure of the prepared composite ceramic powder for thermal spraying can effectively inhibit decomposition of silicon carbide in the thermal spraying process; and the high-entropy cobalt-based alloy on the outer layer has excellent oxidation resistance, so that oxidation of the alloy in the spraying process is avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of ceramic material preparation, and particularly to a preparation method of composite ceramic powder for thermal spraying. Background Art

[0002] Thermal spraying technology is a method of spraying molten or semi-molten spraying materials onto the surface of a substrate at a certain speed to form a coating. With the continuous development of technology, thermal spraying technology has been widely used in fields such as aerospace, automotive manufacturing, and new energy. As an important material in thermal spraying technology, the performance of composite ceramic powder directly affects the overall quality and performance of the coating.

[0003] Traditional composite ceramic powders are usually composed of single materials or simple composite materials, and their structures and properties often fail to meet the requirements under complex working conditions. For example, silicon carbide powder is widely used in thermal spraying coatings due to its high hardness, high wear resistance, and high corrosion resistance. However, silicon carbide powder is prone to decomposition during the thermal spraying process, resulting in a decline in coating performance. In addition, a single silicon carbide coating often fails to meet the requirements of high hardness, high toughness, and high oxidation resistance simultaneously.

[0004] To solve the above problems, researchers have begun to explore composite ceramic powders with a multi-layer structure. Through the combination and transition between different materials, this kind of powder can achieve the optimization and complementarity of various properties. However, there are still some technical problems in the preparation process of existing multi-layer structure composite ceramic powders. For example, the bonding force between layers is not strong enough, resulting in easy peeling and cracking of the coating during use; the selection of materials and structures for the transition layer is inappropriate, unable to effectively inhibit the decomposition of silicon carbide; the oxidation resistance of the outer layer material is insufficient, resulting in easy oxidation of the coating in a high-temperature environment. Summary of the Invention

[0005] The purpose of the present invention is to provide a preparation method of composite ceramic powder for thermal spraying to solve the problems existing in the prior art.

[0006] To solve the above technical problems, the present invention provides the following technical solutions:

[0007] A preparation method of composite ceramic powder for thermal spraying, the preparation method is as follows:

[0008] (1) Chemically corrode the surface of silicon carbide powder to obtain rough silicon carbide;

[0009] (2) Deposit high-entropy carbide on the surface of rough silicon carbide by magnetron sputtering to obtain a silicon carbide / high-entropy carbide composite material;

[0010] (3) Coating a high-entropy oxide precursor on the surface of the silicon carbide / high-entropy carbide composite; subjecting the silicon carbide / high-entropy carbide composite with the surface-coated high-entropy oxide precursor to high-temperature heat treatment in a reducing atmosphere to form a cobalt-based high-entropy alloy on the surface, thereby obtaining the composite ceramic powder for thermal spraying.

[0011] As an optimization, the method of chemical etching in step (1) is as follows: Mix hydrofluoric acid, nitric acid, and pure water in a volume ratio of 1:(3 - 4):(60 - 70) to obtain an etching solution, mix silicon carbide and the etching solution in a mass ratio of 1:(15 - 20), heat up to 90 - 100 °C and etch for 300 min.

[0012] As an optimization, the preparation method of the silicon carbide / high-entropy carbide composite in step (2) is as follows: Using titanium, zirconium, hafnium, vanadium, and tungsten metals as targets, introduce argon into the vacuum chamber, the air pressure in the vacuum chamber is 2×10-3 Pa, then introduce acetylene into the chamber, the acetylene flow rate is 2.5 - 3.0 mL / min, apply a pulsed power supply to the targets, the power of the power supply is 180 W, deposit high-entropy carbide on the rough silicon carbide surface, and the deposition time is 5 min; cool to 40 - 50 °C in a vacuum environment, then fill the chamber with air to atmospheric pressure, open the chamber to take samples to obtain the silicon carbide / high-entropy carbide, and the air pressure in the chamber is maintained at 0.2 - 2.0 Pa during the deposition process.

[0013] As an optimization, the mass of the high-entropy carbide in step (2) is 10% - 50% of the mass of the silicon carbide powder.

[0014] As an optimization, the preparation method of the composite ceramic powder for thermal spraying in step (3) is as follows: Mix metal salts and urea, the molar ratio of the total metal ions to urea is 1:6, add silicon carbide / high-entropy carbide which is 5 - 6 times the mass of urea, then add pure water which is 30 - 40 times the mass of urea, stir well, calcine at 500 °C for 1 h, then wash and dry; perform high-temperature heat treatment in a reducing atmosphere to obtain the composite ceramic powder for thermal spraying.

[0015] As an optimization, the metal salts contain four or more of chromium ions, nickel ions, iron ions, aluminum ions, titanium ions, manganese ions, and copper ions, and also contain cobalt ions; the molar amount of cobalt ions accounts for 20% - 50% of the total metal ions in the metal salts.

[0016] As an optimization, the reducing atmosphere is one of a hydrogen-argon mixed gas, ammonia, and hydrogen; the high-temperature heat treatment temperature is 1000 - 1400 °C, and the time is 3 - 6 h.

[0017] Compared with the prior art, the beneficial effects achieved by the present invention are:

[0018] The composite ceramic powder for thermal spraying prepared by the present invention is composed of a three-layer structure. The inner layer is silicon carbide powder, the middle layer is a high-entropy compound, and the outer layer is a cobalt-based high-entropy alloy. When preparing the composite ceramic powder for thermal spraying, first, through surface corrosion, a rough bonding interface is formed on the surface of the silicon carbide powder to strengthen the bonding force between the silicon carbide core and the high-entropy carbide. Second, the high-entropy compound with high hardness and excellent toughness forms a transition layer between the alloy and the silicon carbide. Finally, the unique core-shell structure of the ceramic powder can effectively inhibit the decomposition of silicon carbide during thermal spraying. The outer high-entropy cobalt-based alloy has excellent oxidation resistance, avoiding the oxidation of the alloy during spraying. Detailed implementation manners

[0019] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0020] Example 1:

[0021] A preparation method of a composite ceramic powder for thermal spraying, characterized in that the preparation method is as follows:

[0022] (1) Chemically corrode the surface of the silicon carbide powder to obtain rough silicon carbide. The method of chemical corrosion is: mix hydrofluoric acid, nitric acid, and pure water in a volume ratio of 1:3:60 to obtain a corrosion solution, mix the silicon carbide and the corrosion solution in a mass ratio of 1:15, heat to 100 °C and corrode for 300 min

[0023] (2) Deposit high-entropy carbide on the surface of the rough silicon carbide by magnetron sputtering to obtain a silicon carbide / high-entropy carbide composite material. The preparation method of the silicon carbide / high-entropy carbide composite material is: use titanium, zirconium, hafnium, vanadium, and tungsten metals as target materials, introduce argon into the vacuum chamber, the air pressure in the vacuum chamber is 2×10 -3 Pa, then introduce acetylene into the chamber, the acetylene flow rate is 2.5 mL / min, apply a pulsed power supply to the target, the power of the power supply is 180 W, deposit high-entropy carbide on the surface of the rough silicon carbide, and the deposition time is 5 min; cool to 50 °C in a vacuum environment, then fill the chamber with air to atmospheric pressure, open the chamber to sample, and obtain silicon carbide / high-entropy carbide. The air pressure in the chamber is maintained at 2.0 Pa during the deposition process;

[0024] (3) Coating a high-entropy oxide precursor on the surface of the silicon carbide / high-entropy carbide composite; performing high-temperature heat treatment on the silicon carbide / high-entropy carbide composite with the high-entropy oxide precursor coated on its surface in a reducing atmosphere to form a cobalt-based high-entropy alloy on the surface, thereby obtaining a composite ceramic powder for thermal spraying; the preparation method of the composite ceramic powder for thermal spraying is as follows: mixing cobalt salt, chromium salt, nickel salt, iron salt, and copper salt to obtain a metal salt, and the molar ratio of cobalt ions, chromium ions, nickel ions, iron ions, and copper ions in the metal salt is 1:1:1:1:1; mixing the metal salt and urea, with the molar ratio of total metal ions to urea being 1:6, adding silicon carbide / high-entropy carbide that is 5 times the mass of urea, and then adding pure water that is 30 times the mass of urea, fully stirring, calcining at 500 °C for 1 h, followed by washing and drying; performing high-temperature heat treatment in a reducing atmosphere to obtain a composite ceramic powder for thermal spraying; the reducing atmosphere is hydrogen; the high-temperature heat treatment temperature is 1400 °C and the time is 6 h.

[0025] Example 2:

[0026] A preparation method of a composite ceramic powder for thermal spraying, the preparation method is as follows:

[0027] (1) Chemically corroding the surface of the silicon carbide powder to obtain rough silicon carbide; the method of chemical corrosion is: mixing hydrofluoric acid, nitric acid, and pure water in a volume ratio of 1:3.5:65 to obtain a corrosion solution, mixing silicon carbide and the corrosion solution in a mass ratio of 1:17, heating to 95 °C and corroding for 300 min

[0028] (2) Depositing high-entropy carbide on the surface of the rough silicon carbide by magnetron sputtering to obtain a silicon carbide / high-entropy carbide composite; the preparation method of the silicon carbide / high-entropy carbide composite is: using titanium, zirconium, hafnium, vanadium, and tungsten metals as targets, introducing argon into the vacuum chamber, with the air pressure in the vacuum chamber being 2×10 -3 Pa, then introducing acetylene into the chamber, with the acetylene flow rate being 2.7 mL / min, applying a pulsed power supply to the targets, with the power of the power supply being 180 W, depositing high-entropy carbide on the surface of the rough silicon carbide, and the deposition time being 5 min; cooling to 45 °C in a vacuum environment, then filling the chamber with air to atmospheric pressure, opening the chamber to take samples to obtain silicon carbide / high-entropy carbide, and the air pressure in the chamber is maintained at 1.0 Pa during the deposition process;

[0029] (3) Coating a high-entropy oxide precursor on the surface of the silicon carbide / high-entropy carbide composite; performing high-temperature heat treatment on the silicon carbide / high-entropy carbide composite with the high-entropy oxide precursor coated on its surface in a reducing atmosphere to form a cobalt-based high-entropy alloy on the surface, thereby obtaining a composite ceramic powder for thermal spraying; the preparation method of the composite ceramic powder for thermal spraying is as follows: mixing cobalt salt, chromium salt, nickel salt, iron salt, and copper salt to obtain a metal salt, wherein the molar ratio of cobalt ions, chromium ions, nickel ions, iron ions, and copper ions in the metal salt is 2:1:1:1:1; mixing the metal salt and urea, with the molar ratio of the total metal ions to urea being 1:6, adding silicon carbide / high-entropy carbide that is 5.5 times the mass of urea, and then adding pure water that is 35 times the mass of urea, fully stirring, calcining at 500 °C for 1 h, washing, and drying; performing high-temperature heat treatment in a reducing atmosphere to obtain the composite ceramic powder for thermal spraying; the reducing atmosphere is ammonia; the high-temperature heat treatment temperature is 1200 °C and the time is 4 h.

[0030] Example 3:

[0031] A preparation method of a composite ceramic powder for thermal spraying, the preparation method is as follows:

[0032] (1) Chemically etching the surface of the silicon carbide powder to obtain rough silicon carbide; the method of chemical etching is: mixing hydrofluoric acid, nitric acid, and pure water in a volume ratio of 1:4:70 to obtain an etching solution, mixing silicon carbide and the etching solution in a mass ratio of 1:20, heating to 90 °C and etching for 300 min;

[0033] (2) Depositing high-entropy carbide on the surface of the rough silicon carbide by magnetron sputtering to obtain a silicon carbide / high-entropy carbide composite; the preparation method of the silicon carbide / high-entropy carbide composite is: using titanium, zirconium, hafnium, vanadium, and tungsten metals as target materials, introducing argon into the vacuum chamber, with the air pressure in the vacuum chamber being 2×10 -3 Pa, then introducing acetylene into the chamber, with the acetylene flow rate being 2.5 mL / min, applying a pulsed power supply to the target material, with the power of the power supply being 180 W, depositing high-entropy carbide on the surface of the rough silicon carbide, and the deposition time being 5 min; cooling to 40 °C in a vacuum environment, then filling the chamber with air to atmospheric pressure, opening the chamber to sample, obtaining silicon carbide / high-entropy carbide, and the air pressure in the chamber is maintained at 0.2 Pa during the deposition process;

[0034] (3) Coating a high-entropy oxide precursor on the surface of the silicon carbide / high-entropy carbide composite; performing high-temperature heat treatment on the silicon carbide / high-entropy carbide composite with the high-entropy oxide precursor coated on its surface in a reducing atmosphere to form a cobalt-based high-entropy alloy on the surface and obtain a composite ceramic powder for thermal spraying; the preparation method of the composite ceramic powder for thermal spraying is as follows: mixing cobalt salt, chromium salt, nickel salt, iron salt, and copper salt to obtain a metal salt, and the molar ratio of cobalt ions, chromium ions, nickel ions, iron ions, and copper ions in the metal salt is 3:1:1:1:1; mixing the metal salt and urea, with the molar ratio of total metal ions to urea being 1:6, adding silicon carbide / high-entropy carbide with a mass 6 times that of urea, and then adding pure water with a mass 40 times that of urea, fully stirring, calcining at 500 °C for 1 h, washing, and drying; performing high-temperature heat treatment in a reducing atmosphere to obtain a composite ceramic powder for thermal spraying; the reducing atmosphere is ammonia; the high-temperature heat treatment temperature is 1000 °C and the time is 3 h.

[0035] Example 4:

[0036] A preparation method of a composite ceramic powder for thermal spraying, and the preparation method is as follows:

[0037] (1) Chemically corroding the surface of the silicon carbide powder to obtain rough silicon carbide; the method of chemical corrosion is: mixing hydrofluoric acid, nitric acid, and pure water according to a volume ratio of 1:3.5:65 to obtain a corrosion solution, mixing silicon carbide and the corrosion solution according to a mass ratio of 1:17, heating to 95 °C and corroding for 300 min

[0038] (2) Depositing high-entropy carbide on the surface of the rough silicon carbide by magnetron sputtering to obtain a silicon carbide / high-entropy carbide composite; the preparation method of the silicon carbide / high-entropy carbide composite is: using titanium, zirconium, hafnium, vanadium, and tungsten metals as targets, introducing argon into the vacuum chamber, with the air pressure in the vacuum chamber being 2×10 -3 Pa, then introducing acetylene into the chamber, with the acetylene flow rate being 2.7 mL / min, applying a pulsed power supply to the targets, with the power of the power supply being 180 W, depositing high-entropy carbide on the surface of the rough silicon carbide, and the deposition time being 5 min; cooling to 45 °C in a vacuum environment, then filling the chamber with air to atmospheric pressure, opening the chamber to take samples to obtain silicon carbide / high-entropy carbide, and the air pressure in the chamber is maintained at 1.0 Pa during the deposition process;

[0039] (3) Coating the surface of the silicon carbide / high-entropy carbide composite with a high-entropy oxide precursor; performing high-temperature heat treatment on the silicon carbide / high-entropy carbide composite with the surface-coated high-entropy oxide precursor in a reducing atmosphere to form a cobalt-based high-entropy alloy on the surface, thereby obtaining a composite ceramic powder for thermal spraying; the preparation method of the composite ceramic powder for thermal spraying is as follows: mixing cobalt salt, chromium salt, nickel salt, titanium salt, and aluminum salt to obtain a metal salt, and the molar ratio of cobalt ions, chromium ions, nickel ions, titanium ions, and aluminum ions in the metal salt is 2:1:1:1:1; mixing the metal salt and urea, and the molar ratio of the total metal ions to urea is 1:6, adding silicon carbide / high-entropy carbide with a mass 5.5 times that of urea, then adding pure water with a mass 35 times that of urea, fully stirring, calcining at 500 °C for 1 h, washing, and drying; performing high-temperature heat treatment in a reducing atmosphere to obtain a composite ceramic powder for thermal spraying; the reducing atmosphere is ammonia; the high-temperature heat treatment temperature is 1200 °C and the time is 4 h.

[0040] Comparative Example 1:

[0041] A preparation method of a composite ceramic powder for thermal spraying, the preparation method is as follows:

[0042] (1) Depositing high-entropy carbide on the surface of silicon carbide by magnetron sputtering to obtain a silicon carbide / high-entropy carbide composite; the preparation method of the silicon carbide / high-entropy carbide composite is as follows: using titanium, zirconium, hafnium, vanadium, and tungsten metals as targets, introducing argon into the vacuum chamber, the air pressure in the vacuum chamber is 2×10-3 Pa, then introducing acetylene into the chamber, the acetylene flow rate is 2.7 mL / min, applying a pulsed power supply to the target, the power of the power supply is 180 W, depositing high-entropy carbide on the rough silicon carbide surface, and the deposition time is 5 min; cooling to 45 °C in a vacuum environment, then filling the chamber with air to atmospheric pressure, opening the chamber to take samples, obtaining silicon carbide / high-entropy carbide, and the air pressure in the chamber is maintained at 1.0 Pa during the deposition process;

[0043] (2) Coating a high-entropy oxide precursor on the surface of the silicon carbide / high-entropy carbide composite; performing high-temperature heat treatment on the silicon carbide / high-entropy carbide composite coated with the high-entropy oxide precursor in a reducing atmosphere to form a cobalt-based high-entropy alloy on the surface, thereby obtaining a composite ceramic powder for thermal spraying; the preparation method of the composite ceramic powder for thermal spraying is as follows: mixing cobalt salt, chromium salt, nickel salt, iron salt, and copper salt to obtain a metal salt, and the molar ratio of cobalt ions, chromium ions, nickel ions, iron ions, and copper ions in the metal salt is 2:1:1:1:1; mixing the metal salt and urea, and the molar ratio of the total metal ions to urea is 1:6, adding silicon carbide / high-entropy carbide that is 5.5 times the mass of urea, and then adding pure water that is 35 times the mass of urea, fully stirring, calcining at 500 °C for 1 h, washing, and drying; performing high-temperature heat treatment in a reducing atmosphere to obtain a composite ceramic powder for thermal spraying; the reducing atmosphere is ammonia; the high-temperature heat treatment temperature is 1200 °C and the time is 4 h.

[0044] Comparative Example 2:

[0045] A preparation method of a composite ceramic powder for thermal spraying, characterized in that the preparation method is as follows:

[0046] (1) Chemically etching the surface of the silicon carbide powder to obtain rough silicon carbide; the method of chemical etching is as follows: mixing hydrofluoric acid, nitric acid, and pure water according to a volume ratio of 1:3.5:65 to obtain an etching solution, mixing silicon carbide and the etching solution according to a mass ratio of 1:17, heating to 95 °C and etching for 300 min.

[0047] (3) Coating a high-entropy oxide precursor on the surface of the rough silicon carbide; performing high-temperature heat treatment on the rough silicon carbide coated on the surface in a reducing atmosphere to form a cobalt-based high-entropy alloy on the surface, thereby obtaining a composite ceramic powder for thermal spraying; the preparation method of the composite ceramic powder for thermal spraying is as follows: mixing cobalt salt, chromium salt, nickel salt, iron salt, and copper salt to obtain a metal salt, and the molar ratio of cobalt ions, chromium ions, nickel ions, iron ions, and copper ions in the metal salt is 2:1:1:1:1; mixing the metal salt and urea, and the molar ratio of the total metal ions to urea is 1:6, adding rough silicon carbide that is 5.5 times the mass of urea, and then adding pure water that is 35 times the mass of urea, fully stirring, calcining at 500 °C for 1 h, washing, and drying; performing high-temperature heat treatment in a reducing atmosphere to obtain a composite ceramic powder for thermal spraying; the reducing atmosphere is ammonia; the high-temperature heat treatment temperature is 1200 °C and the time is 4 h.

[0048] Comparative Example 3:

[0049] A preparation method of a composite ceramic powder for thermal spraying, the preparation method is as follows:

[0050] (1) Chemically etch the surface of the silicon carbide powder to obtain rough silicon carbide; the method of chemical etching is as follows: Mix hydrofluoric acid, nitric acid, and pure water in a volume ratio of 1:3.5:65 to obtain an etching solution, mix silicon carbide and the etching solution in a mass ratio of 1:17, heat to 95 °C and etch for 300 min;

[0051] (2) Deposit high-entropy carbide on the surface of rough silicon carbide by magnetron sputtering to obtain a silicon carbide / high-entropy carbide composite; the preparation method of the silicon carbide / high-entropy carbide composite is as follows: Use titanium, zirconium, hafnium, vanadium, and tungsten metals as target materials, introduce argon into the vacuum chamber, the air pressure in the vacuum chamber is 2×10-3 Pa, then introduce acetylene into the chamber, the acetylene flow rate is 2.7 mL / min, apply a pulsed power supply to the target, the power of the power supply is 180 W, deposit high-entropy carbide on the surface of rough silicon carbide, and the deposition time is 5 min; Cool to 45 °C in a vacuum environment, then fill the chamber with air to atmospheric pressure, open the chamber to take samples to obtain the composite ceramic powder for spraying, and the air pressure in the chamber is maintained at 1.0 Pa during the deposition process.

[0052] Test Example 1:

[0053] Test of oxidation resistance:

[0054] Test method: Prepare a coating from the ceramic powders obtained in the examples and comparative examples using a Diamond Jet2600 supersonic flame spraying system; The coating substrate is made of 304 stainless steel. First, degrease and remove rust from the substrate to ensure that the substrate surface is pollution-free, and then sandblast the substrate with corundum particles; The spraying parameters are as follows: The spray gun model is DJ2600; The hydrogen flow rate is 635 L / min, the oxygen flow rate is 280 L / min; The compressed air flow rate is 345 L / min; The carrier gas argon flow rate is 25 L / min, the powder feeding speed is 32 g / min, the moving speed is 90 m / min, and the spraying distance is 250 mm; In this experiment, the calcination method is used to test the oxidation resistance of the composite ceramic powders obtained in the examples and comparative examples. Use a precision balance to measure the mass of the substrate with the coating before calcination, put the substrate with the coating into an electric furnace and calcine it in an air environment, and measure the mass of the sample after calcination after cooling. The calcination temperature is 1000 °C and the calcination time is 90 h. Calculate the oxidation weight gain per unit area. The greater the weight gain, the worse the oxidation resistance of the powder, and vice versa. The results are shown in Table 1.

[0055] Table 1

[0056] <![CDATA[Mass (mg / cm 2 )]]> <![CDATA[Mass (mg / cm 2 )]]> Example 1 2.6 Comparative Example 1 2.8 Example 2 2.7 Comparative Example 2 6.4 Example 3 2.7 Comparative Example 3 6.8 Example 4 2.6

[0057] From the comparison of the experimental data of Examples 1-4 and Comparative Examples 1-3 in Table 1, it can be found that the composite ceramic powder prepared by the present invention has good oxidation resistance.

[0058] By comparison, the weight gain of Examples 1 to 4 is less than that of Comparative Example 1, indicating that the unique core-shell structure of the ceramic powder can effectively inhibit the decomposition of silicon carbide during thermal spraying; the outer high-entropy cobalt-based alloy has excellent oxidation resistance, avoiding the oxidation of the alloy during spraying.

[0059] Test Example 2:

[0060] Test of wear resistance:

[0061] Test method: The ceramic powders prepared in the examples and comparative examples were used to prepare coatings by a Diamond Jet 2600 supersonic flame spraying system; the coating substrate was made of 304 stainless steel. First, the substrate was degreased and derusted to ensure that the substrate surface was pollution-free, and then the substrate was sandblasted with corundum particles; the spraying parameters were as follows: the spray gun model was DJ2600; the hydrogen flow rate was 635 L / min, the oxygen flow rate was 280 L / min; the compressed air flow rate was 345 L / min; the carrier gas argon flow rate was 25 L / min, the powder feeding speed was 32 g / min, the moving speed was 90 m / min, and the spraying distance was 250 mm; a high-temperature friction and wear testing machine was used, the load was set to 10 N, the rotation speed was 364 / min, the test time was 5 min, and the mass loss of the coating after the experiment was measured, which was used as an index of the wear resistance of the coating; the results are shown in Table 2.

[0062] Table 2

[0063] Mass loss (mg) <![CDATA[Mass loss (mg / cm 2 )]]> Example 1 1.8 Comparative Example 1 2.1 Example 2 1.7 Comparative Example 2 3.7 Example 3 1.7 Comparative Example 3 3.6 Example 4 1.7

[0064] From the comparison of the experimental data of Examples 1 to 4 and Comparative Examples 1 to 3 in Table 2, it can be found that the composite ceramic powder prepared by the present invention has good wear resistance.

[0065] By comparison, the mass loss of Examples 1 to 4 is less than that of Comparative Example 1, indicating that the composite ceramic powder for thermal spraying prepared by the present invention is composed of a three-layer structure, with a silicon carbide powder layer on the inner layer, a high-entropy compound layer in the middle, and a cobalt-based high-entropy alloy layer on the outer layer; the combination of the three materials can provide excellent wear resistance.

[0066] Test Example 3

[0067] Test of toughness:

[0068] Test method: The ceramic powders prepared in the examples and comparative examples were used to prepare coatings by a Diamond Jet 2600 supersonic flame spraying system; the coating substrate was made of 304 stainless steel. First, the substrate was degreased and derusted to ensure that the substrate surface was pollution-free, and then the substrate was sandblasted with corundum particles; the spraying parameters were as follows: the spray gun model was DJ2600; the hydrogen flow rate was 635 L / min, the oxygen flow rate was 280 L / min; the compressed air flow rate was 345 L / min; the carrier gas argon flow rate was 25 L / min, the powder feeding speed was 32 g / min, the moving speed was 90 m / min, and the spraying distance was 250 mm; a Vickers hardness tester was used to perform indentation tests on the coatings, and the maximum loading load was 25 g to judge the toughness of the coatings. The results are shown in Table 4.

[0069] Table 4

[0070] Coating appearance Coating appearance Example 1 No obvious cracks Comparative Example 1 Tiny cracks Example 2 No obvious cracks Comparative Example 2 Slightly larger cracks Example 3 No obvious cracks Comparative Example 3 Tiny cracks

[0071] From the comparison of the experimental data of Examples 1-4 and Comparative Examples 1-3 in Table 4, it can be found that the composite ceramic powder prepared by the present invention has good toughness.

[0072] By comparison, the appearance of the coatings prepared in Examples 1-4 is complete, indicating that. The composite ceramic powder for thermal spraying prepared by the present invention is composed of a three-layer structure, with a silicon carbide powder layer on the inner layer, a high-entropy compound layer in the middle, and a cobalt-based high-entropy alloy layer on the outer layer; through surface corrosion, a rough bonding interface is formed on the surface of the silicon carbide powder to strengthen the bonding force between the silicon carbide core and the high-entropy carbide; the high-entropy compound with high hardness and excellent toughness forms a transition layer between the alloy and the silicon carbide; the outer high-entropy cobalt-based alloy has excellent hardness; the combination of the three-layer materials can provide excellent toughness.

[0073] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and without departing from the spirit or basic characteristics of the present invention, the present invention can be implemented in other specific forms. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present invention. Any reference signs in the claims should not be construed as limiting the claimed rights.

Claims

1. A method for preparing a composite ceramic powder for thermal spraying, characterized in that: The preparation method is as follows: (1) chemically etching the surface of silicon carbide powder to obtain rough silicon carbide; (2) depositing high entropy carbide on the rough silicon carbide surface by magnetron sputtering to obtain a silicon carbide / high entropy carbide composite material; (3) coating a high entropy oxide precursor on the surface of a silicon carbide / high entropy carbide composite material; subjecting the silicon carbide / high entropy carbide composite material coated with the high entropy oxide precursor to high-temperature heat treatment in a reducing atmosphere to form a cobalt-based high entropy alloy on the surface, thereby obtaining a composite ceramic powder for thermal spraying.

2. The method for preparing a composite ceramic powder for thermal spraying according to claim 1, characterized in that: The chemical etching method of step (1) is as follows: hydrofluoric acid, nitric acid and pure water are mixed in a volume ratio of 1: (3-4): (60-70) to obtain an etching solution, silicon carbide and the etching solution are mixed in a mass ratio of 1: (15-20), and the temperature is raised to 90-100° C. for etching for 300 minutes.

3. The method for preparing a composite ceramic powder for thermal spraying according to claim 1, characterized in that: The preparation method of the silicon carbide / high entropy carbide composite material in step (2) is as follows: titanium zirconium hafnium vanadium tungsten metal is used as a target material, argon gas is introduced into a vacuum chamber, and the vacuum chamber pressure is 2×10 -3 Pa, and then acetylene is introduced into the cavity with an acetylene flow rate of 2.5-3.0mL / min, a pulse power supply is applied to the target with a power of 180W, and high entropy carbide is deposited on the rough silicon carbide surface for 5 minutes; it is cooled to 40-50°C in a vacuum environment, and then air is filled into the cavity to atmospheric pressure, the cavity is opened for sampling, and silicon carbide / high entropy carbide is obtained. During the deposition process, the air pressure in the cavity is maintained at 0.2-2.0Pa.

4. The method for preparing a composite ceramic powder for thermal spraying according to claim 1, characterized in that: The mass of the high entropy carbide in step (2) is 10%-50% of the mass of the silicon carbide powder.

5. The method for preparing a composite ceramic powder for thermal spraying according to claim 1, characterized in that: The preparation method of the composite ceramic powder for thermal spraying in step (3) is as follows: metal salt and urea are mixed, the molar ratio of total metal ions to urea is 1:6, silicon carbide / high entropy carbide is added in an amount of 5-6 times the mass of urea, and pure water is added in an amount of 30-40 times the mass of urea, after being fully stirred, calcined at 500°C for 1h, washed and dried; and high-temperature heat treatment is performed in a reducing atmosphere to obtain the composite ceramic powder for thermal spraying.

6. The method for preparing a composite ceramic powder for thermal spraying according to claim 5, characterized in that: The metal salt contains four or more of chromium ions, nickel ions, iron ions, aluminum ions, titanium ions, manganese ions, and copper ions, and also contains cobalt ions; the molar amount of the cobalt ions accounts for 20%-50% of the total metal ions in the metal salt.

7. The method for preparing a composite ceramic powder for thermal spraying according to claim 5, characterized in that: The reducing atmosphere is one of hydrogen-argon mixed gas, ammonia and hydrogen; the high temperature heat treatment temperature is 1000-1400° C., and the time is 3-6 hours.