阅读说明：本技术 一种石墨材料表面耐高温抗氧化涂层及其制备方法 (High-temperature-resistant and antioxidant coating on surface of graphite material and preparation method thereof ) 是由 薛文东 匡健磊 吴佩霞 于 2020-10-30 设计创作，主要内容包括：本发明公开了一种石墨材料表面耐高温抗氧化涂层及其制备方法,其中的石墨材料表面耐高温抗氧化涂层制备方法包括：按质量份数取碳化硅、有机锆材料、有机硼材料、有机钽材料、乙炔碳黑及有机硅消泡剂。将有机锆材料、有机硼材料、有机钽材料混合均匀,获得涂料溶剂。将碳化硅、乙炔碳黑加入至所述涂料溶剂中并加入有机硅消泡剂,制得耐高温抗氧化涂料；将耐高温抗氧化涂料涂覆在石墨材料表面,并低温烘烤；将石墨材料转移至气氛烧结炉内进行中温热解；调节气氛烧结炉内的氩气气氛及温度,启动高温碳热还原反应；碳热还原反应结束后进行高温烧结；烧结结束后即可在石墨材料表面制得一定厚度的耐高温抗氧化涂层。(The invention discloses a high-temperature-resistant and antioxidant coating on the surface of a graphite material and a preparation method thereof, wherein the preparation method of the high-temperature-resistant and antioxidant coating on the surface of the graphite material comprises the following steps: silicon carbide, an organic zirconium material, an organic boron material, an organic tantalum material, acetylene carbon black and an organic silicon defoaming agent are taken according to the mass parts. And (3) uniformly mixing the organic zirconium material, the organic boron material and the organic tantalum material to obtain the coating solvent. Adding silicon carbide and acetylene black into the coating solvent and adding an organic silicon defoamer to prepare the high-temperature-resistant and antioxidant coating; coating the high-temperature-resistant anti-oxidation coating on the surface of a graphite material, and baking at low temperature; transferring the graphite material into an atmosphere sintering furnace for medium-temperature pyrolysis; adjusting the argon atmosphere and temperature in the atmosphere sintering furnace, and starting a high-temperature carbothermic reduction reaction; sintering at high temperature after the carbothermic reduction reaction is finished; after sintering, a high-temperature-resistant and oxidation-resistant coating with a certain thickness can be prepared on the surface of the graphite material.)

1. A preparation method of a high-temperature-resistant and antioxidant coating on the surface of a graphite material is characterized by comprising the following steps:

taking 70-100 parts of silicon carbide, 10-30 parts of an organic zirconium material, 10-30 parts of an organic boron material, 5-10 parts of an organic tantalum material, 5-30 parts of acetylene carbon black and 1-3 parts of an organic silicon defoaming agent by mass;

uniformly mixing an organic zirconium material, an organic boron material and an organic tantalum material to obtain a coating solvent;

adding silicon carbide and acetylene black into the coating solvent, stirring at a high speed for 0.5-2 hours under the ice-water bath condition, adding an organic silicon defoaming agent, and continuously stirring for 0.5-1 hour to prepare a high-temperature-resistant antioxidant coating;

coating the high-temperature-resistant antioxidant coating on the surface of a graphite material to obtain a wet film with a certain thickness, and baking at a low temperature of 80-95 ℃ for 6-8 hours;

transferring the graphite material coated with the high-temperature-resistant anti-oxidation coating into an atmosphere sintering furnace, and carrying out medium-temperature pyrolysis at the temperature of 250-400 ℃ in the argon atmosphere of 0.2-1 Mpa for 1-2 hours;

reducing the argon atmosphere in the atmosphere sintering furnace to 0.01-0.05 MPa, heating to 1300-1600 ℃, and carrying out high-temperature carbothermic reduction reaction for 1-3 hours;

after the carbothermic reduction reaction is finished, increasing the pressure intensity of the argon atmosphere to 3-10 MPa, and continuing to perform high-temperature sintering at 1300-1600 ℃ for 1-3 hours;

and after sintering, cooling to room temperature at a cooling rate of 1-5 ℃/min, and thus obtaining the high-temperature-resistant and antioxidant coating with a certain thickness on the surface of the graphite material.

2. The method for preparing the high-temperature-resistant and antioxidant coating on the surface of the graphite material as claimed in claim 1, wherein the organic zirconium material is one or more of zirconium n-butoxide, zirconium n-propoxide, zirconium acetylacetonate, zirconocene dichloride and zirconium tetra (dimethylammonium) chloride.

3. The method for preparing the high-temperature-resistant and antioxidant coating on the surface of the graphite material as claimed in claim 1, wherein the organoboron material is one or more of triisopropyl borate, triethyl borate, dichlorophenylborane, triethylamine borane and trimethylamine borane.

4. The preparation method of the high-temperature-resistant and antioxidant coating on the surface of the graphite material as claimed in claim 1, wherein the organic tantalum material is one or more of tantalum isopropoxide, tantalum trifluoroethanol, tantalum ethoxide and tantalum penta-n-butoxide.

5. The method for preparing the high-temperature-resistant and antioxidant coating on the surface of the graphite material according to claim 1, wherein the particle size of the silicon carbide is 100-1000 nm, and the particle size of the acetylene black is 10-50 nm.

6. The method for preparing the high-temperature-resistant and oxidation-resistant coating on the surface of the graphite material according to claim 1, wherein the coating thickness of the wet film is 300-2000 microns.

7. The method for preparing the high-temperature-resistant and oxidation-resistant coating on the surface of the graphite material according to claim 1, wherein the thickness of the high-temperature-resistant and oxidation-resistant coating is 100-800 micrometers.

8. A high-temperature-resistant and oxidation-resistant coating on the surface of a graphite material, which is characterized by being prepared by the preparation method of the high-temperature-resistant and oxidation-resistant coating on the surface of the graphite material according to any one of claims 1 to 7.

Technical Field

The invention belongs to the field of material technology, and particularly relates to a high-temperature-resistant and antioxidant coating on the surface of a graphite material and a preparation method thereof.

Background

The graphite material has good chemical corrosion resistance, high electric and heat conductivity, excellent mechanical property, low density, small thermal expansion coefficient and high thermal stability. Therefore, the graphite material is a common high-temperature material and is widely applied to the fields of aerospace, metal smelting, refractory materials, nuclear power industry, petroleum machinery and the like. However, graphite is easily oxidized in a high-temperature environment. Although graphite materials can be used in inert or vacuum atmospheres above 2000 ℃, rapid oxidation begins above 500 ℃ in air or oxygen-containing atmospheres. This severely limits its application in high temperature areas and results in waste and consumption of valuable graphite resources. Therefore, it is necessary to improve the oxidation resistance of graphite and prolong the service life thereof.

The preparation of a layer of high-temperature-resistant and oxidation-resistant coating material on the surface of a graphite material is a main way and method for improving the oxidation resistance of the graphite material. The method does not change the composition, structure and preparation process of the graphite material, thereby having minimal influence on the production and application of the graphite material. The high-temperature resistant oxidation-resistant coating is mainly used for preventing oxygen from diffusing to the graphite material, so that the oxidation of the graphite material is avoided. In order to improve the oxidation resistance as much as possible, the coating material itself must first of all have excellent high-temperature resistance and oxidation resistance, it must also be able to produce a tight bond with the graphite material, and the coefficients of expansion of the two must not differ too much. According to the above requirements, materials represented by ultra-high temperature ceramics such as silicon carbide, tantalum carbide, zirconium boride and the like are potential high temperature resistant and oxidation resistant coating materials. Chinese patent publication No. CN109824374B discloses a method for preparing a high-performance silicon carbide coating on the surface of a carbon-carbon composite thermal insulation material, which comprises coating polycarbosilane, xylene and silicon powder as a coating on the surface of a carbon material, carrying out ceramic sintering treatment at 900 ℃, depositing carbon on the surface of the ceramic sintered coating material by using propylene as a carbon source and nitrogen as a diluent gas, and finally reacting silicon in the ceramic sintered coating with the deposited carbon through a 1500 ℃ sintering reaction to generate a silicon carbide coating. Chinese patent document with publication number CN110357635A discloses a method for improving the bonding strength of an oxidation-resistant coating on the surface of a carbon-based or ceramic-based composite material, which comprises the steps of firstly preparing a SiC bottom layer on the surface of a substrate material by using a CVD process; carrying out pre-oxidation treatment on the substrate material deposited with the SiC to form silicon oxide on the surface of the substrate material; preparing slurry by using boron oxide, silicon dioxide, silicon carbide, zirconium boride, alumina powder and silica sol as raw materials, and preparing an ultrahigh-temperature ceramic anti-oxidation intermediate layer on the surface of a pre-oxidized sample by using a slurry brushing-sintering process; and finally depositing an outer SiC layer on the surface of the sample. The two methods need a complex gas phase process, and have high cost and long time consumption.

Chinese patent publication No. CN111334743A discloses a method for preparing a zirconium boride-zirconium carbide-silicon carbide composite coating, which comprises performing sand blasting or sand paper polishing on an inorganic non-metallic substrate, and then preparing a zirconium boride-zirconium carbide-silicon carbide composite coating on the surface of the inorganic non-metallic material by thermal spraying using zirconium/boron carbide/silicon carbide composite powder or zirconium oxide/boron carbide/aluminum/silicon carbide composite powder as a raw material. The high temperature caused by the thermal spraying process is easy to cause the oxidation damage of the graphite material.

Chinese patent publication No. CN109678516A discloses an oxidation-resistant graphite electrode surface coating and a preparation process thereof, wherein silicon carbide, zirconium oxide, aluminum oxide, methanol, ethanol, stearic acid as a dispersant and acrylic resin as a binder are used as raw materials to prepare a coating according to a certain proportion, and the coating is coated on the surface of a graphite electrode and then sintered at 1500-1800 ℃ to prepare the oxidation-resistant coating. The CN111233483A patent provides a silicon carbide coating for sagger and a preparation method thereof, which takes silicon carbide powder, metal oxide, kaolin, graphite, polyacrylate, binder, water or ethanol as raw materials, heats up in a reaction kettle, stirs and mixes, cools and screens to obtain the silicon carbide coating. The CN110498684A patent provides a preparation method of a silicon carbide coating, which is a silicon carbide coating prepared by coating the surface of a graphite material with polycarbosilane and xylene as primer and silicon carbide powder, silica sol, carbon black powder and yttrium oxide powder as silicon carbide coating slurry and then sintering at 1550-1600 ℃. The metal oxide is added in the three methods mainly for reducing the sintering temperature, but the oxide is easy to form liquid phase evaporation loss at high temperature in the service process of the coating, and finally holes are formed.

Chinese patent publication No. CN110409170A discloses a method for preparing a ZrB2 coating on the surface of carbon fiber, which comprises the steps of preparing a coating by using polyvinyl alcohol, boric acid, inorganic zirconium salt and deionized water as raw materials, coating the coating on the surface of the carbon fiber, and reacting at 1200-1400 ℃ to obtain the ZrB2 coating. The CN110396817A patent further adds an inorganic hafnium salt to prepare HfZrB2 coating. In the two methods, deionized water is used as a solvent to prepare the coating, and the surface of the carbon material is not hydrophilic, so that the coating is easily uneven and runs off, and the final coating is uneven and not compact.

Disclosure of Invention

Aiming at the defects in the prior art, the invention provides a preparation method of a high-temperature-resistant and antioxidant coating on the surface of a graphite material, and the technical scheme is as follows:

a preparation method of a high-temperature-resistant and oxidation-resistant coating on the surface of a graphite material comprises the following steps:

taking 70-100 parts of silicon carbide, 10-30 parts of an organic zirconium material, 10-30 parts of an organic boron material, 5-10 parts of an organic tantalum material, 5-30 parts of acetylene carbon black and 1-3 parts of an organic silicon defoaming agent by mass;

uniformly mixing an organic zirconium material, an organic boron material and an organic tantalum material to obtain a coating solvent;

adding silicon carbide and acetylene black into the coating solvent, stirring at a high speed for 0.5-2 hours under the ice-water bath condition, adding an organic silicon defoaming agent, and continuously stirring for 0.5-1 hour to prepare a high-temperature-resistant antioxidant coating;

coating the high-temperature-resistant antioxidant coating on the surface of a graphite material to obtain a wet film with a certain thickness, and baking at a low temperature of 80-95 ℃ for 6-8 hours;

transferring the graphite material coated with the high-temperature-resistant anti-oxidation coating into an atmosphere sintering furnace, and carrying out medium-temperature pyrolysis at the temperature of 250-400 ℃ in the argon atmosphere of 0.2-1 Mpa for 1-2 hours;

reducing the argon atmosphere in the atmosphere sintering furnace to 0.01-0.05 MPa, heating to 1300-1600 ℃, and carrying out high-temperature carbothermic reduction reaction for 1-3 hours;

after the carbothermic reduction reaction is finished, increasing the pressure intensity of the argon atmosphere to 3-10 MPa, and continuing to perform high-temperature sintering at 1300-1600 ℃ for 1-3 hours;

and after sintering, cooling to room temperature at a cooling rate of 1-5 ℃/min, and thus obtaining the high-temperature-resistant and antioxidant coating with a certain thickness on the surface of the graphite material.

In some embodiments, the organozirconium material is one or more of zirconium n-butoxide, zirconium n-propoxide, zirconium acetylacetonate, zirconocene dichloride, and zirconium tetrakis (dimethylammonium) chloride.

In some embodiments, the organoboron material is one or more of triisopropyl borate, triethyl borate, dichlorophenylborane, triethylamine borane, and trimethylamine borane.

In some embodiments, the organic tantalum material is one or more of tantalum isopropoxide, tantalum trifluoroethanol, tantalum ethoxide and tantalum penta-n-butoxide.

In some embodiments, the silicon carbide has a particle size of 100 to 1000 nm, and the acetylene black has a particle size of 10 to 50 nm.

In some embodiments, the wet film is coated to a thickness of 300 to 2000 microns.

In some embodiments, the thickness of the high temperature resistant and oxidation resistant coating is 100-800 microns.

The invention also provides a high-temperature-resistant and antioxidant coating on the surface of the graphite material, which is prepared by the preparation method of the high-temperature-resistant and antioxidant coating on the surface of the graphite material.

Compared with the prior art, the invention has the beneficial effects that:

1. taking an organic zirconium material, an organic boron material and an organic tantalum material as zirconium, boron and tantalum sources in the high-temperature-resistant anti-oxidation coating; meanwhile, compared with water-based paint, the organic material is also used as a solvent, so that better affinity to the graphite material can be realized, the organic material is favorable for spreading and permeating into pores on the surface of the graphite material, a foundation is provided for subsequent reaction of the pyrolysis product of the organic material and the surface of the graphite material, and the formation of tight chemical combination is facilitated.

2. The high-temperature pyrolysis intermediate products of the organozirconium material, the organoboron material and the organotantalum material have higher activity, can realize the carbothermic reduction reaction with the surface of the graphite material and the acetylene black in the coating under the condition of lower temperature, and simultaneously are chemically combined with the surface of the silicon carbide to finally form the high-temperature resistant and antioxidant coating consisting of the silicon carbide-zirconium boride-tantalum carbide multiphase ultrahigh-temperature ceramics.

Detailed Description

The description is further elucidated with reference to specific examples. The description is to be regarded as illustrative and explanatory only and should not be taken as limiting the scope of the invention in any way.

Example 1

The preparation method of the high-temperature-resistant and oxidation-resistant coating on the surface of the graphite material in the embodiment comprises the following steps:

10 parts of n-butyl zirconium, 10 parts of triethyl borate and 5 parts of tantalum ethoxide are weighed and mixed uniformly to be used as a coating solvent.

70 parts of silicon carbide (with the grain diameter of 1000 nanometers) and 5 parts of acetylene black (with the grain diameter of 50 nanometers) are weighed and mixed, added into a coating solvent, stirred at a high speed for 0.5 hour under the condition of ice-water bath, and then added with 1 part of organic silicon defoamer and continuously stirred for 0.5 hour to prepare the high-temperature-resistant antioxidant coating.

Coating the high-temperature-resistant anti-oxidation coating on the surface of a graphite material to obtain a wet film with the thickness of 2000 mu m, and then baking at the low temperature of 95 ℃ for 8 hours.

And transferring the graphite material coated with the high-temperature-resistant anti-oxidation coating into an atmosphere sintering furnace, and carrying out medium-temperature pyrolysis at 250 ℃ under the atmosphere of 1Mpa argon for 2 hours.

And continuously heating to 1300 ℃ for carrying out high-temperature carbothermic reduction reaction, wherein the reaction time is 1 hour, the reaction atmosphere is argon atmosphere, and the pressure of the argon atmosphere is 0.01 MPa.

After the carbothermic reduction reaction is finished, the pressure of the argon atmosphere is increased to 3MPa, and high-temperature sintering is continuously carried out at 1300 ℃, wherein the sintering time is 1 hour.

And after sintering, cooling to room temperature at the rate of 1 ℃/minute to obtain the high-temperature-resistant and oxidation-resistant coating with the thickness of 620 mu m on the surface of the graphite material.

The coating prepared by the embodiment is uniform and compact, has no cracks, and the binding force between the composite coating and the graphite material reaches 47.2 Mpa. Through test comparison, after heat preservation is carried out for 10 hours at 1400 ℃ in air atmosphere, the ablation rate of the graphite material without the coating is more than or equal to 99.9 percent, and the ablation rate of the graphite material with the composite coating on the surface is less than or equal to 0.3 percent.

Example 2

The preparation method of the high-temperature-resistant and oxidation-resistant coating on the surface of the graphite material in the embodiment comprises the following steps:

25 parts of zirconium n-propoxide, 30 parts of dichlorophenylborane and 10 parts of tantalum pentan-butoxide are weighed and mixed uniformly to be used as a coating solvent.

100 parts of silicon carbide (with the grain diameter of 100 nanometers) and 30 parts of acetylene black (with the grain diameter of 10 nanometers) are weighed and mixed, added into a coating solvent, stirred at a high speed for 2 hours under the condition of ice-water bath, then added with 3 parts of organic silicon defoamer and continuously stirred for 1 hour to prepare the high-temperature-resistant antioxidant coating.

Coating the high-temperature-resistant anti-oxidation coating on the surface of a graphite material to obtain a wet film with the thickness of 300 mu m, and then baking at the low temperature of 80 ℃ for 6 hours.

And transferring the graphite material coated with the high-temperature-resistant anti-oxidation coating into an atmosphere sintering furnace, and carrying out medium-temperature pyrolysis at 400 ℃ under the argon atmosphere of 0.2Mpa for 1 hour.

And continuously heating to 1600 ℃ to carry out high-temperature carbothermic reduction reaction for 3 hours, wherein the reaction atmosphere is argon atmosphere, and the pressure of the argon atmosphere is 0.05 MPa.

After the carbothermic reduction reaction is finished, the pressure of the argon atmosphere is increased to 10MPa, and high-temperature sintering is continuously carried out at 1600 ℃ for 3 hours.

And after sintering, cooling to room temperature at the rate of 5 ℃/min to obtain the high-temperature-resistant and oxidation-resistant coating with the thickness of 140 mu m on the surface of the graphite material.

The coating prepared by the embodiment is uniform and compact, has no cracks, and the binding force between the composite coating and the graphite material reaches 61.7 Mpa. Through test comparison, after heat preservation is carried out for 10 hours at 1400 ℃ in air atmosphere, the ablation rate of the graphite material without the coating is more than or equal to 99.9 percent, and the ablation rate of the graphite material with the composite coating on the surface is less than or equal to 0.8 percent.

Example 3

The preparation method of the high-temperature-resistant and oxidation-resistant coating on the surface of the graphite material in the embodiment comprises the following steps:

30 parts of zirconocene dichloride, 15 parts of triethylamine borane and 8 parts of tantalum isopropoxide are weighed and mixed uniformly to be used as a coating solvent.

85 parts of silicon carbide (with the grain diameter of 500 nanometers) and 15 parts of acetylene black (with the grain diameter of 40 nanometers) are weighed and mixed, added into a coating solvent, stirred at a high speed for 1 hour under the condition of ice-water bath, then added with 2 parts of an organic silicon defoamer and continuously stirred for 1 hour to prepare the high-temperature-resistant antioxidant coating.

Coating the high-temperature-resistant anti-oxidation coating on the surface of a graphite material to obtain a wet film with the thickness of 1000 mu m, and then baking at the low temperature of 90 ℃ for 7 hours.

And transferring the graphite material coated with the high-temperature-resistant anti-oxidation coating into an atmosphere sintering furnace, and carrying out medium-temperature pyrolysis at 300 ℃ under the argon atmosphere of 0.6Mpa for 1.5 hours.

And continuously heating to 1500 ℃ to perform high-temperature carbothermic reduction reaction for 2 hours, wherein the reaction atmosphere is argon atmosphere, and the pressure of the argon atmosphere is 0.04 MPa.

After the carbothermic reduction reaction is finished, the pressure of the argon atmosphere is increased to 8MPa, and high-temperature sintering is continuously carried out at 1500 ℃, wherein the sintering time is 2 hours.

And after sintering, cooling to room temperature at the rate of 4 ℃/min to obtain a high-temperature-resistant and oxidation-resistant coating with the thickness of 440 mu m on the surface of the graphite material.

The coating prepared by the embodiment is uniform and compact, has no cracks, and the bonding force between the composite coating and the graphite material reaches 56.5 Mpa. Through test comparison, after heat preservation is carried out for 10 hours at 1400 ℃ in air atmosphere, the ablation rate of the graphite material without the coating is more than or equal to 99.9 percent, and the ablation rate of the graphite material with the composite coating on the surface is less than or equal to 0.6 percent.

Example 4

The preparation method of the high-temperature-resistant and oxidation-resistant coating on the surface of the graphite material in the embodiment comprises the following steps:

20 parts of zirconium acetylacetonate, 20 parts of triisopropyl borate and 7 parts of tantalum trifluoroethanol are weighed and mixed uniformly to be used as a coating solvent.

80 parts of silicon carbide (with the grain diameter of 800 nanometers) and 20 parts of acetylene black (with the grain diameter of 30 nanometers) are weighed and mixed, added into a coating solvent, stirred at a high speed for 1 hour under the condition of ice-water bath, then added with 3 parts of organic silicon defoamer and continuously stirred for 1 hour to prepare the high-temperature-resistant antioxidant coating.

Coating the high-temperature-resistant anti-oxidation coating on the surface of a graphite material to obtain a wet film with the thickness of 1500 mu m, and then baking at the low temperature of 95 ℃ for 8 hours.

And transferring the graphite material coated with the high-temperature-resistant anti-oxidation coating into an atmosphere sintering furnace, and carrying out medium-temperature pyrolysis at 350 ℃ under the argon atmosphere of 0.4Mpa for 2 hours.

And continuously heating to 1550 ℃ to perform high-temperature carbothermic reduction reaction for 2.5 hours, wherein the reaction atmosphere is argon atmosphere, and the pressure of the argon atmosphere is 0.03 MP.

After the carbothermic reduction reaction is finished, the pressure of the argon atmosphere is increased to 9MPa, and high-temperature sintering is continuously carried out at 1550 ℃ for 2.5 hours.

And after sintering, cooling to room temperature at the rate of 2 ℃/min to obtain a high-temperature-resistant and oxidation-resistant coating with the thickness of 560 microns on the surface of the graphite material.

The coating prepared by the embodiment is uniform and compact, has no cracks, and the binding force between the composite coating and the graphite material reaches 51.9 Mpa. Through test comparison, after heat preservation is carried out for 10 hours at 1400 ℃ in air atmosphere, the ablation rate of the graphite material without the coating is more than or equal to 99.9 percent, and the ablation rate of the graphite material with the composite coating on the surface is less than or equal to 0.4 percent.

Example 5

The preparation method of the high-temperature-resistant and oxidation-resistant coating on the surface of the graphite material in the embodiment comprises the following steps:

22 parts of zirconium tetra (dimethyl ammonium), 25 parts of trimethylamine borane and 9 parts of tantalum trifluoroethanol are weighed and mixed uniformly to be used as a coating solvent.

85 parts of silicon carbide (with the grain diameter of 700 nanometers) and 25 parts of acetylene black (with the grain diameter of 25 nanometers) are weighed and mixed, added into a coating solvent, stirred at a high speed for 1 hour under the condition of ice-water bath, and then added with 2 parts of an organic silicon defoamer and continuously stirred for 1 hour to prepare the high-temperature-resistant antioxidant coating.

Coating the high-temperature-resistant anti-oxidation coating on the surface of a graphite material to obtain a wet film with the thickness of 1200 mu m, and then baking at the low temperature of 92 ℃ for 7 hours.

And transferring the graphite material coated with the high-temperature-resistant anti-oxidation coating into an atmosphere sintering furnace, and carrying out medium-temperature pyrolysis at 330 ℃ under the argon atmosphere of 0.5Mpa for 2 hours.

And continuously heating to 1450 ℃ for carrying out high-temperature carbothermic reduction reaction for 2.5 hours, wherein the reaction atmosphere is argon atmosphere, and the pressure of the argon atmosphere is 0.02 MP.

After the carbothermic reduction reaction is finished, the pressure of the argon atmosphere is increased to 7MPa, and high-temperature sintering is continuously carried out at 1550 ℃ for 2.5 hours.

And after sintering, cooling to room temperature at the rate of 2 ℃/min to obtain the high-temperature-resistant and oxidation-resistant coating with the thickness of 360 mu m on the surface of the graphite material.

The coating prepared by the embodiment is uniform and compact, has no cracks, and the binding force between the composite coating and the graphite material reaches 65.8 Mpa. Through test comparison, after heat preservation is carried out for 10 hours at 1400 ℃ in air atmosphere, the ablation rate of the graphite material without the coating is more than or equal to 99.9 percent, and the ablation rate of the graphite material with the composite coating on the surface is less than or equal to 0.5 percent.

The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.