A graphite device surface composite tantalum carbide coating and a coating method thereof

Abstract

The present application relates to the technical field of carbon coating, and discloses a graphite device surface composite tantalum carbide coating and a coating method thereof, which comprises a carbon layer, an intermediate tantalum carbide layer and a tantalum carbide outer layer arranged in sequence along the graphite device surface outward; the intermediate tantalum carbide layer is obtained by reacting tantalum oxide, tantalum carbide and PVA glue in any proportion; and the tantalum carbide outer layer is obtained by reacting 2-8% of the mass fraction of tantalum chloride, 0.3-0.8% of the mass fraction of chromium carbide, 2-10% of the mass fraction of PVA glue and 15-25% of the mass fraction of ethylene glycol. The graphite device surface composite tantalum carbide coating in the present application can form a graphite device surface composite tantalum carbide coating with stronger binding force and higher surface finish through the mutual bonding effect between the multiple composite coatings, and the preparation process conditions are relatively lower.

Description

Technical Field

[0001] This invention relates to the field of carbon material coating technology, and more specifically, to a composite tantalum carbide coating on the surface of a graphite device and its coating method. Background Technology

[0002] Graphite is a typical layered material, with carbon atoms arranged in layers. Each carbon atom is equidistant from its neighboring atoms, and the carbon atoms in each layer are arranged in hexagonal rings. The hexagonal rings of adjacent layers are displaced in parallel with each other and then stacked to form a layered structure. Different directions and distances of displacement result in different structures. Due to its structural characteristics, graphite possesses properties such as high temperature resistance, electrical and thermal conductivity, good chemical stability, and high plasticity, and is therefore widely used in materials for high-temperature metallurgy, electrical conductivity, and electronics.

[0003] With the expansion of application scenarios and the improvement of usage requirements, the requirements for graphite-based devices are also becoming increasingly stringent. Among these requirements, the tolerance of graphite devices to extreme environments has become one of the most significant issues. Currently, the material properties of graphite devices are often improved by coating the surface of the graphite device. For example, patent CN113735627A proposes a graphite thermal field material with a tantalum carbide coating and its preparation method. High-purity tantalum powder and high-purity graphene are blended under high pressure and then sprayed onto the surface of a graphite part. Through high-temperature infiltration, a tantalum carbide coating is formed.

[0004] However, existing technologies such as coating tantalum carbide onto the surface of graphite devices have problems such as low adhesion between the tantalum carbide coating and the graphite device, poor surface finish of the coating, and the need for high sintering temperature to achieve coating preparation, which means that the requirements for process conditions and production equipment are high.

[0005] Therefore, there is an urgent need for a tantalum carbide coating for graphite devices with stronger coating adhesion, better coating surface finish, and lower process requirements, as well as its preparation method. Summary of the Invention

[0006] The technical problem to be solved by this invention:

[0007] In existing tantalum carbide coatings prepared on the surface of graphite devices, the bonding ability between the tantalum carbide coating and the graphite device is poor due to limitations in coating materials and preparation processes. Furthermore, the surface finish of the final tantalum carbide coating is poor. The coating sintering process requires high sintering temperatures, which limits the use of graphite devices and the production of tantalum carbide coatings on their surfaces.

[0008] The technical solution adopted in this invention is as follows:

[0009] This invention provides a composite tantalum carbide coating on the surface of a graphite device. Along the surface of the graphite device outwards, the composite tantalum carbide coating comprises a carbon layer, an intermediate tantalum carbide layer, and an outer tantalum carbide layer sequentially deposited. The intermediate tantalum carbide layer is obtained by reacting tantalum oxide, tantalum carbide, and PVA adhesive in any proportion. The outer tantalum carbide layer, by mass fraction, is obtained by reacting 2-8% tantalum chloride, 0.3-0.8% chromium carbide, 2-10% PVA adhesive, and 15-25% ethylene glycol.

[0010] Preferably, the thickness of the carbon layer is ≤20μm.

[0011] Preferably, the carbon layer is formed by sintering carbon powder with a particle size of 0.08-0.12 μm.

[0012] Preferably, the thickness of the intermediate tantalum carbide layer is ≤50μm.

[0013] Preferably, the thickness of the tantalum carbide outer layer is 20-40 μm.

[0014] The present invention also provides a method for coating the surface of the above-mentioned graphite device with a composite tantalum carbide coating, comprising the following steps:

[0015] S1 mixes carbon powder with adhesive and water, sprays and granulates to obtain spherical powder; then plasma-sprays the spherical powder onto the surface of a graphite substrate to form a carbon layer;

[0016] S2 mixes tantalum oxide and tantalum carbide, adds PVA adhesive and water, mixes and granulates to obtain a mixed powder; the mixed powder is plasma sprayed onto the surface of the carbon layer to form an intermediate tantalum carbide layer;

[0017] S3 mixes tantalum carbide, tantalum chloride, chromium carbide, PVA adhesive, ethylene glycol and water and ball-mills them to obtain a composite slurry; the composite slurry is then coated onto the surface of the intermediate tantalum carbide layer in multiple layers to form the outer tantalum carbide layer;

[0018] S4 The graphite substrate, after being processed in steps S1, S2 and S3, is placed in a heating furnace, preheated, and then heated in stages to 1920-1980℃ for reaction. After cooling, a graphite device with the composite tantalum carbide coating on its surface is obtained.

[0019] Preferably, in step S1, the particle size of the spherical powder is 0.1-2 μm.

[0020] Preferably, in step S3, the composite slurry is coated onto the surface of the intermediate tantalum carbide layer in 4-8 applications.

[0021] Preferably, after each coating is completed, the product is baked at 130-160°C, cooled to room temperature, and then coated again.

[0022] Preferably, in step S4, the temperature is first kept at 200-220℃ for 0.8-1.2h, then raised to 780-820℃ and kept for 0.3-0.8h, and finally raised to 1920-1980℃ and kept for 4-6h.

[0023] The beneficial effects of this invention are as follows:

[0024] The graphite device of this invention is coated with a multi-layer composite coating consisting of a carbon layer, an intermediate tantalum carbide layer, and an outer tantalum carbide layer. The plasma-sprayed carbon layer exhibits excellent adhesion to the graphite device substrate and can react with the subsequently applied tantalum oxide-containing coating during the high-temperature sintering stage. This allows the tantalum oxide liquid phase to diffuse into the carbon layer and react with the carbon to form tantalum carbide. The tantalum carbide generated in this process is tightly integrated with the carbon layer, thus improving the overall adhesion of the composite coating. Furthermore, the composite slurry of the outer tantalum carbide layer can graft TaOxCy active sintering sites onto the surface of the tantalum carbide in the intermediate and outer layers, further promoting the adhesion and diffusion of tantalum carbide particles during the high-temperature sintering stage. The chromium carbide within the sintering layer forms a liquid phase at the sintering temperature, thereby reducing the coating sintering temperature and resulting in a smooth and glossy outermost surface of the composite coating. Overall, this invention, through the mutual bonding between the multi-layer composite coatings, can form a composite tantalum carbide coating on the graphite device surface with stronger adhesion and higher surface smoothness, while requiring relatively lower processing conditions. Attached Figure Description

[0025] Figure 1 This is a photograph of the surface morphology of the graphite device sample in Example 1 after scratching.

[0026] Figure 2 The image shows the surface morphology of the graphite device sample in Comparative Example 1 after it has been scratched.

[0027] Figure 3 The image shows the surface morphology of the graphite device sample in Comparative Example 2 after it has been scratched. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0029] This invention provides a composite tantalum carbide coating on the surface of a graphite device, comprising, outwardly along the surface of the graphite device, a carbon layer, an intermediate tantalum carbide layer, and an outer tantalum carbide layer sequentially deposited; the carbon layer is formed by sintering carbon powder with a particle size of 0.08-0.12μm, the intermediate tantalum carbide layer is obtained by reacting tantalum oxide, tantalum carbide, and PVA adhesive, and the outer tantalum carbide layer is obtained by reacting tantalum chloride, chromium carbide, PVA (polyvinyl alcohol) adhesive, and ethylene glycol.

[0030] In this invention, the carbon powder in the carbon layer has a particle size of 0.08-0.12 μm and is granulated into spherical powder with a particle size of 1-2 μm. The spherical powder is then coated to form the carbon layer.

[0031] In this invention, the thickness of the carbon layer does not exceed 20 μm, the thickness of the intermediate tantalum carbide layer does not exceed 50 μm, and the thickness of the outer tantalum carbide layer is 20-40 μm.

[0032] In this invention, the tantalum carbide slurry in the outer layer of tantalum carbide, by weight, comprises 0.3-0.8 wt% chromium carbide, 2-10 wt% PVA powder, 2-8 wt% TaCl5, 15-25 wt% ethylene glycol, and the balance tantalum carbide.

[0033] The present invention also provides a method for coating the surface of the above-mentioned graphite device with a composite tantalum carbide coating, comprising the following steps:

[0034] (1) Mix 0.1-0.5μm spherical carbon powder with PVA glue and water, and granulate by plasma spraying to form spherical powder with a particle size of 0.1-2μm; during granulation, control the inlet temperature of the granulation equipment to be 180-220℃, the outlet temperature to be 90-100℃, the solid content of the slurry to be 50-65%, the pressure of the feed pump to be 1.5-2.5 bar, and the feed flow rate to be 20-35L / h;

[0035] A graphite substrate is taken, cleaned, and polished. Using argon as the carrier gas, spherical powder is sprayed onto the surface of the graphite substrate to form a carbon layer through high-temperature plasma spraying. The preferred parameters of the plasma spraying equipment are: power 30kW, spraying distance 80mm, spraying angle 60°, and powder feeding rate 30g / min.

[0036] (2) Tantalum carbide and Ta2O5 are mixed as raw materials, 2-5wt% of PVA adhesive is added, and 2-5mL / g of water is added to make a slurry. The mixture is then granulated in a gas spray granulation equipment to obtain a mixed powder. During granulation, the inlet temperature of the granulation equipment is controlled at 220-250℃, the outlet temperature is controlled at 110-130℃, the solid content of the slurry is controlled at 55-60%, the pressure of the feed pump is controlled at 1.5-2.5bar, and the feed flow rate is controlled at 30-50L / h.

[0037] On the surface of a graphite substrate with a carbon layer, a mixed powder is sprayed onto the substrate using plasma spraying to form an intermediate tantalum carbide layer.

[0038] (3) Mix tantalum carbide, chromium carbide, TaCl5 (tantalum chloride), ethylene glycol, and PVA adhesive, add pure water, mix and ball mill to make a composite slurry;

[0039] On the surface of a graphite substrate with a carbon layer and an intermediate tantalum carbide layer, a composite slurry is applied in small amounts and multiple times to form an outer tantalum carbide layer. The number of coatings is 4-8 times, the total coating thickness is 20-40μm, and each coating is baked at 130-160℃ and cooled to room temperature before the next coating is applied.

[0040] The coating method can be brushing or spraying, with spraying being the preferred method to achieve a uniform coating thickness.

[0041] (4) The graphite substrate with carbon layer-intermediate tantalum carbide layer-outer tantalum carbide layer is placed in a heating furnace and vacuum-heated at 200-220℃ for 0.8-1.2h, then heated to 780-820℃ and held for 0.3-0.8h, then filled with argon and heated to 1920-1980℃ and held for 4-6h, and then cooled to room temperature to obtain a stone grinding device with a composite tantalum carbide coating on the surface.

[0042] <Example>

[0043] Example 1

[0044] Step 1: Mix carbon powder with a particle size of less than 0.5 μm, 5% PVA adhesive, and 10% water to form a slurry; use a spray granulator, adjust the inlet temperature to 200℃, the outlet temperature to 95℃, the slurry solid content to 50%, the feed pump pressure to 2.0 bar, and the feed flow rate to 30 L / h; then, through air classification, finally make the slurry into spherical powder with a particle size of less than 2 μm.

[0045] Step 2: Using the spherical powder prepared in Step 1 as raw material, argon as carrier gas, powder flow rate of 15 g / min, arc gun working voltage of 60 V, distance between nozzle end face and graphite device surface of 130 mm, relative moving speed between spray gun and graphite device surface of 12 m / min, a 5 μm thick carbon layer is plasma sprayed on graphite device surface.

[0046] Step 3: By mass fraction, mix 85wt% Ta2O5 and 15wt% TaC as raw materials, add 3.5wt% PVA adhesive by mass of the raw materials, and then add 3.5mL / g water to mix and prepare the slurry. Perform gas spray granulation on the granulation equipment. The inlet temperature of the granulation equipment is 240℃, the outlet temperature is 120℃, the solid content of the slurry is 60%, the feed pump pressure is 2.0bar, and the feed flow rate is 40L / h. Then, through air classification, a mixed powder with a particle size of less than 20μm is produced.

[0047] Step 4: Using the mixed powder prepared in Step 3 as raw material, argon as carrier gas, powder flow rate of 10 g / min, arc gun working voltage of 60 V, distance between nozzle end face and graphite device surface of 100 mm, and relative moving speed between spray gun and graphite device surface of 10 m / min, a 10 μm thick intermediate tantalum carbide layer is plasma sprayed onto the carbon layer surface obtained in Step 2.

[0048] Step 5: Mix 0.5wt% Cr3C2, 5wt% PVA adhesive, 5wt% TaCl5, 20wt% ethylene glycol and the balance tantalum carbide by mass fraction, add pure water at a solid-liquid ratio of 3g / mL, and ball mill for 2 hours to obtain composite slurry A.

[0049] Step 6: Mix 3wt% PVA adhesive, 10wt% ethylene glycol and the balance tantalum carbide by mass fraction, add pure water at a solid-liquid ratio of 2g / mL, and ball mill for 0.5h to obtain composite slurry B.

[0050] Step 7: Apply composite slurry A to the surface of the intermediate tantalum carbide layer obtained in step 4, dividing it into two brushings, and baking it at 150°C for 10 minutes after each brushing; then apply composite slurry B, dividing it into six brushings, and baking it at 150°C for 10 minutes after each brushing.

[0051] Step 8: Place the graphite device with composite coating obtained in Step 7 into a vacuum high-temperature furnace, first heat it to 200℃ and hold it for 1 hour, then continue heating it to 800℃ and hold it for 0.5 hours, then fill it with argon gas and continue heating it to 1950℃ and hold it for 5 hours, then cool it to room temperature to obtain a graphite device with a composite tantalum carbide coating on its surface.

[0052] Example 2

[0053] Step 1: Mix carbon powder with a particle size of less than 0.5 μm, 5% PVA adhesive, and 10% water to form a slurry; use a spray granulator, adjust the inlet temperature to 200℃, the outlet temperature to 95℃, the slurry solid content to 50%, the feed pump pressure to 2.0 bar, and the feed flow rate to 30 L / h; then, through air classification, finally make the slurry into spherical powder with a particle size of less than 2 μm.

[0054] Step 2: Using the spherical powder prepared in Step 1 as raw material, argon as carrier gas, powder flow rate of 15 g / min, arc gun working voltage of 60 V, distance between nozzle end face and graphite device surface of 130 mm, relative moving speed between spray gun and graphite device surface of 12 m / min, a 5 μm thick carbon layer is plasma sprayed on graphite device surface.

[0055] Step 3: By mass fraction, mix 20wt% Ta2O5 and 80wt% TaC as raw materials, add 3.5wt% PVA adhesive by mass of the raw materials, and then add 3.5mL / g water to mix and prepare the slurry. Perform gas spray granulation on the granulation equipment. The inlet temperature of the granulation equipment is 240℃, the outlet temperature is 120℃, the solid content of the slurry is 60%, the feed pump pressure is 2.0bar, and the feed flow rate is 40L / h. Then, through air classification, a mixed powder with a particle size of less than 20μm is produced.

[0056] Step 4: Using the mixed powder prepared in Step 3 as raw material, argon as carrier gas, powder flow rate of 10 g / min, arc gun working voltage of 60 V, distance between nozzle end face and graphite device surface of 100 mm, and relative moving speed between spray gun and graphite device surface of 10 m / min, a 10 μm thick intermediate tantalum carbide layer is plasma sprayed onto the carbon layer surface obtained in Step 2.

[0057] Step 5: Mix 0.5wt% Cr3C2, 5wt% PVA adhesive, 5wt% TaCl5, 20wt% ethylene glycol and the balance tantalum carbide by mass fraction, add pure water at a solid-liquid ratio of 3g / mL, and ball mill for 2 hours to obtain composite slurry A.

[0058] Step 6: Mix 3wt% PVA adhesive, 10wt% ethylene glycol and the balance tantalum carbide by mass fraction, add pure water at a solid-liquid ratio of 2g / mL, and ball mill for 0.5h to obtain composite slurry B.

[0059] Step 7: Apply composite slurry A to the surface of the intermediate tantalum carbide layer obtained in step 4, dividing it into two brushings, and baking it at 150°C for 10 minutes after each brushing; then apply composite slurry B, dividing it into six brushings, and baking it at 150°C for 10 minutes after each brushing.

[0060] Step 8: Place the graphite device with composite coating obtained in Step 7 into a vacuum high-temperature furnace, first heat it to 200℃ and hold it for 1 hour, then continue heating it to 800℃ and hold it for 0.5 hours, then fill it with argon gas and continue heating it to 1950℃ and hold it for 5 hours, then cool it to room temperature to obtain a graphite device with a composite tantalum carbide coating on its surface.

[0061] Example 3

[0062] Step 1: Mix carbon powder with a particle size of less than 0.5 μm, 5% PVA adhesive, and 10% water to form a slurry; use a spray granulator, adjust the inlet temperature to 200℃, the outlet temperature to 95℃, the slurry solid content to 50%, the feed pump pressure to 2.0 bar, and the feed flow rate to 30 L / h; then, through air classification, finally make the slurry into spherical powder with a particle size of less than 2 μm.

[0063] Step 2: Using the spherical powder prepared in Step 1 as raw material, argon as carrier gas, powder flow rate of 15 g / min, arc gun working voltage of 60 V, distance between nozzle end face and graphite device surface of 130 mm, relative moving speed between spray gun and graphite device surface of 12 m / min, a 5 μm thick carbon layer is plasma sprayed on graphite device surface.

[0064] Step 3: By mass fraction, mix 30wt% Ta2O5 and 70wt% TaC as raw materials, add 3.5wt% PVA adhesive by mass of the raw materials, and then add 3.5mL / g water to mix and prepare the slurry. Perform gas spray granulation on the granulation equipment. The inlet temperature of the granulation equipment is 240℃, the outlet temperature is 120℃, the solid content of the slurry is 60%, the feed pump pressure is 2.0bar, and the feed flow rate is 40L / h. Then, through air classification, a mixed powder with a particle size of less than 20μm is produced.

[0065] Step 4: Using the mixed powder prepared in Step 3 as raw material, argon as carrier gas, powder flow rate of 10 g / min, arc gun working voltage of 60 V, distance between nozzle end face and graphite device surface of 100 mm, and relative moving speed between spray gun and graphite device surface of 10 m / min, a 10 μm thick intermediate tantalum carbide layer is plasma sprayed onto the carbon layer surface obtained in Step 2.

[0066] Step 5: Mix 0.5wt% Cr3C2, 5wt% PVA adhesive, 5wt% TaCl5, 20wt% ethylene glycol and the balance tantalum carbide by mass fraction, add pure water at a solid-liquid ratio of 3g / mL, and ball mill for 2 hours to obtain composite slurry A.

[0067] Step 6: Mix 3wt% PVA adhesive, 10wt% ethylene glycol and the balance tantalum carbide by mass fraction, add pure water at a solid-liquid ratio of 2g / mL, and ball mill for 0.5h to obtain composite slurry B.

[0068] Step 7: Apply composite slurry A to the surface of the intermediate tantalum carbide layer obtained in step 4, dividing it into two brushings, and baking it at 150°C for 10 minutes after each brushing; then apply composite slurry B, dividing it into six brushings, and baking it at 150°C for 10 minutes after each brushing.

[0069] Step 8: Place the graphite device with composite coating obtained in Step 7 into a vacuum high-temperature furnace, first heat it to 200℃ and hold it for 1 hour, then continue heating it to 800℃ and hold it for 0.5 hours, then fill it with argon gas and continue heating it to 1950℃ and hold it for 5 hours, then cool it to room temperature to obtain a graphite device with a composite tantalum carbide coating on its surface.

[0070] Example 4

[0071] Step 1: Mix carbon powder with a particle size of less than 0.5 μm, 5% PVA adhesive, and 10% water to form a slurry; use a spray granulator, adjust the inlet temperature to 200℃, the outlet temperature to 95℃, the slurry solid content to 50%, the feed pump pressure to 2.0 bar, and the feed flow rate to 30 L / h; then, through air classification, finally make the slurry into spherical powder with a particle size of less than 2 μm.

[0072] Step 2: Using the spherical powder prepared in Step 1 as raw material, argon as carrier gas, powder flow rate of 15 g / min, arc gun working voltage of 60 V, distance between nozzle end face and graphite device surface of 130 mm, relative moving speed between spray gun and graphite device surface of 12 m / min, a 5 μm thick carbon layer is plasma sprayed on graphite device surface.

[0073] Step 3: By mass fraction, mix 40wt% Ta2O5 and 60wt% TaC as raw materials, add 3.5wt% PVA adhesive by mass of the raw materials, and then add 3.5mL / g water to mix and prepare the slurry. Perform gas spray granulation on the granulation equipment. The inlet temperature of the granulation equipment is 240℃, the outlet temperature is 120℃, the solid content of the slurry is 60%, the feed pump pressure is 2.0bar, and the feed flow rate is 40L / h. Then, through air classification, a mixed powder with a particle size of less than 20μm is produced.

[0074] Step 4: Using the mixed powder prepared in Step 3 as raw material, argon as carrier gas, powder flow rate of 10 g / min, arc gun working voltage of 60 V, distance between nozzle end face and graphite device surface of 100 mm, and relative moving speed between spray gun and graphite device surface of 10 m / min, a 10 μm thick intermediate tantalum carbide layer is plasma sprayed onto the carbon layer surface obtained in Step 2.

[0075] Step 5: Mix 0.3wt% Cr3C2, 3.2wt% PVA adhesive, 2.5wt% TaCl5, 20wt% ethylene glycol and the balance tantalum carbide by mass fraction, add pure water at a solid-liquid ratio of 3g / mL, and ball mill for 2 hours to obtain composite slurry A.

[0076] Step 6: Mix 3wt% PVA adhesive, 10wt% ethylene glycol and the balance tantalum carbide by mass fraction, add pure water at a solid-liquid ratio of 2g / mL, and ball mill for 0.5h to obtain composite slurry B.

[0077] Step 7: Apply composite slurry A to the surface of the intermediate tantalum carbide layer obtained in step 4, dividing it into two brushings, and baking it at 150°C for 10 minutes after each brushing; then apply composite slurry B, dividing it into six brushings, and baking it at 150°C for 10 minutes after each brushing.

[0078] Step 8: Place the graphite device with composite coating obtained in Step 7 into a vacuum high-temperature furnace, first heat it to 200℃ and hold it for 1 hour, then continue heating it to 800℃ and hold it for 0.5 hours, then fill it with argon gas and continue heating it to 1950℃ and hold it for 5 hours, then cool it to room temperature to obtain a graphite device with a composite tantalum carbide coating on its surface.

[0079] Example 5

[0080] Step 1: Mix carbon powder with a particle size of less than 0.5 μm, 5% PVA adhesive, and 10% water to form a slurry; use a spray granulator, adjust the inlet temperature to 200℃, the outlet temperature to 95℃, the slurry solid content to 50%, the feed pump pressure to 2.0 bar, and the feed flow rate to 30 L / h; then, through air classification, finally make the slurry into spherical powder with a particle size of less than 2 μm.

[0081] Step 2: Using the spherical powder prepared in Step 1 as raw material, argon as carrier gas, powder flow rate of 15 g / min, arc gun working voltage of 60 V, distance between nozzle end face and graphite device surface of 130 mm, relative moving speed between spray gun and graphite device surface of 12 m / min, a 5 μm thick carbon layer is plasma sprayed on graphite device surface.

[0082] Step 3: By mass fraction, mix 25wt% Ta2O5 and 75wt% TaC as raw materials, add 3.5wt% PVA adhesive by mass of the raw materials, and then add 3.5mL / g water to mix and prepare the slurry. Perform gas spray granulation on the granulation equipment. The inlet temperature of the granulation equipment is 240℃, the outlet temperature is 120℃, the solid content of the slurry is 60%, the feed pump pressure is 2.0bar, and the feed flow rate is 40L / h. Then, through air classification, a mixed powder with a particle size of less than 20μm is produced.

[0083] Step 4: Using the mixed powder prepared in Step 3 as raw material, argon as carrier gas, powder flow rate of 10 g / min, arc gun working voltage of 60 V, distance between nozzle end face and graphite device surface of 100 mm, and relative moving speed between spray gun and graphite device surface of 10 m / min, a 10 μm thick intermediate tantalum carbide layer is plasma sprayed onto the carbon layer surface obtained in Step 2.

[0084] Step 5: Mix 0.7wt% Cr3C2, 8.3wt% PVA adhesive, 7.5wt% TaCl5, 20wt% ethylene glycol and the balance tantalum carbide by mass fraction, add pure water at a solid-liquid ratio of 3g / mL, and ball mill for 2 hours to obtain composite slurry A.

[0085] Step 6: Mix 3wt% PVA adhesive, 10wt% ethylene glycol and the balance tantalum carbide by mass fraction, add pure water at a solid-liquid ratio of 2g / mL, and ball mill for 0.5h to obtain composite slurry B.

[0086] Step 7: Apply composite slurry A to the surface of the intermediate tantalum carbide layer obtained in step 4, dividing it into two brushings, and baking it at 150°C for 10 minutes after each brushing; then apply composite slurry B, dividing it into six brushings, and baking it at 150°C for 10 minutes after each brushing.

[0087] Step 8: Place the graphite device with composite coating obtained in Step 7 into a vacuum high-temperature furnace, first heat it to 200℃ and hold it for 1 hour, then continue heating it to 800℃ and hold it for 0.5 hours, then fill it with argon gas and continue heating it to 1950℃ and hold it for 5 hours, then cool it to room temperature to obtain a graphite device with a composite tantalum carbide coating on its surface.

[0088] Example 6

[0089] Step 1: Mix carbon powder with a particle size of less than 0.5 μm, 5% PVA adhesive, and 10% water to form a slurry; use a spray granulator, adjust the inlet temperature to 200℃, the outlet temperature to 95℃, the slurry solid content to 50%, the feed pump pressure to 2.0 bar, and the feed flow rate to 30 L / h; then, through air classification, finally make the slurry into spherical powder with a particle size of less than 2 μm.

[0090] Step 2: Using the spherical powder prepared in Step 1 as raw material, argon as carrier gas, powder flow rate of 15 g / min, arc gun working voltage of 60 V, distance between nozzle end face and graphite device surface of 130 mm, relative moving speed between spray gun and graphite device surface of 12 m / min, a 5 μm thick carbon layer is plasma sprayed on graphite device surface.

[0091] Step 3: By mass fraction, mix 15wt% Ta2O5 and 85wt% TaC as raw materials, add 3.5wt% PVA adhesive by mass of the raw materials, and then add 3.5mL / g water to mix and prepare the slurry. Perform gas spray granulation on the granulation equipment. The inlet temperature of the granulation equipment is 240℃, the outlet temperature is 120℃, the solid content of the slurry is 60%, the feed pump pressure is 2.0bar, and the feed flow rate is 40L / h. Then, through air classification, a mixed powder with a particle size of less than 20μm is produced.

[0092] Step 4: Using the mixed powder prepared in Step 3 as raw material, argon as carrier gas, powder flow rate of 10 g / min, arc gun working voltage of 60 V, distance between nozzle end face and graphite device surface of 100 mm, and relative moving speed between spray gun and graphite device surface of 10 m / min, a 10 μm thick intermediate tantalum carbide layer is plasma sprayed onto the carbon layer surface obtained in Step 2.

[0093] Step 5: Mix 0.5wt% Cr3C2, 4.2wt% PVA adhesive, 5wt% TaCl5, 15wt% ethylene glycol and the balance tantalum carbide by mass fraction, add pure water at a solid-liquid ratio of 3g / mL, and ball mill for 2 hours to obtain a composite slurry.

[0094] Step 6: Apply composite slurry to the surface of the intermediate tantalum carbide layer obtained in step 4, dividing it into 6 brushings, and baking it at 150°C for 10 minutes after each brushing.

[0095] Step 7: Place the graphite device with composite coating obtained in Step 6 in a vacuum high-temperature furnace, first heat it to 200℃ and hold it for 1 hour, then continue heating it to 800℃ and hold it for 0.5 hours, then fill it with argon gas and continue heating it to 1950℃ and hold it for 5 hours, then cool it to room temperature to obtain a graphite device with a composite tantalum carbide coating on its surface.

[0096] <Comparative Example>

[0097] Comparative Example 1

[0098] Step 1: By mass fraction, mix 85wt% Ta2O5 and 15wt% TaC as raw materials, add 3.5wt% PVA adhesive by mass of the raw materials, and then add 3.5mL / g water to mix and prepare the slurry. Perform gas spray granulation on the granulation equipment. The inlet temperature of the granulation equipment is 240℃, the outlet temperature is 120℃, the solid content of the slurry is 50%, the feed pump pressure is 2.0bar, and the feed flow rate is 30L / h. Then, through air classification, a mixed powder with a particle size of less than 20μm is produced.

[0099] Step 2: Using the mixed powder prepared in Step 1 as raw material, argon as carrier gas, the powder flow rate is 10 g / min, the arc gun working voltage is 60 V, the distance between the nozzle end face and the graphite device surface is 100 mm, and the relative moving speed between the spray gun and the graphite device surface is 10 m / min, a 10 μm thick tantalum layer is plasma sprayed on the graphite device surface.

[0100] Step 3: Mix 0.5wt% Cr3C2, 5wt% PVA adhesive, 5wt% TaCl5, 20wt% ethylene glycol and the balance tantalum carbide by mass fraction, add pure water at a solid-liquid ratio of 3g / mL, and ball mill for 2 hours to obtain composite slurry A.

[0101] Step 4: Mix 3wt% PVA adhesive, 10wt% ethylene glycol and the balance tantalum carbide by mass fraction, add pure water at a solid-liquid ratio of 2g / mL, and ball mill for 0.5h to obtain composite slurry B.

[0102] Step 5: Apply composite slurry A to the tantalum layer obtained in step 2, dividing it into two brushings, and bake it at 150°C for 10 minutes after each brushing; then apply composite slurry B, dividing it into six brushings, and bake it at 150°C for 10 minutes after each brushing.

[0103] Step Six: Place the graphite device with composite coating obtained in Step Five into a vacuum high-temperature furnace, first heat it to 200℃ and hold it for 1 hour, then continue heating it to 800℃ and hold it for 0.5 hours, then fill it with argon gas and continue heating it to 1950℃ and hold it for 5 hours, then cool it to room temperature to obtain a graphite device with a composite tantalum carbide coating on its surface.

[0104] Comparative Example 2

[0105] Step 1: Mix carbon powder with a particle size of less than 0.5μm, 5% PVA adhesive, and 10% water to form a slurry. Use a spray granulator, adjust the inlet temperature to 200℃, the outlet temperature to 95℃, the slurry solid content to 50%, the feed pump pressure to 2.0 bar, and the feed flow rate to 30L / h. Then, through air classification, the slurry is finally made into spherical powder with a particle size of less than 2μm.

[0106] Step 2: Using the spherical powder prepared in Step 1 as raw material, argon as carrier gas, powder flow rate of 15 g / min, arc gun working voltage of 60 V, distance between nozzle end face and graphite device surface of 130 mm, relative moving speed between spray gun and graphite device surface of 12 m / min, a 5 μm thick carbon layer is plasma sprayed on graphite device surface.

[0107] Step 3: Mix 0.5wt% Cr3C2, 5wt% PVA adhesive, 5wt% TaCl5, 20wt% ethylene glycol and the balance tantalum carbide by mass fraction, add pure water at a solid-liquid ratio of 3g / mL, and ball mill for 2 hours to obtain composite slurry A.

[0108] Step 4: Mix 3wt% PVA adhesive, 10wt% ethylene glycol and the balance tantalum carbide by mass fraction, add pure water at a solid-liquid ratio of 2g / mL, and ball mill for 0.5h to obtain composite slurry B.

[0109] Step 5: Apply composite slurry A to the carbon layer obtained in step 2, dividing it into two equal parts, and bake it at 150°C for 10 minutes after each application; then apply composite slurry B, dividing it into six equal parts, and bake it at 150°C for 10 minutes after each application.

[0110] Step Six: Place the graphite device with composite coating obtained in Step Five into a vacuum high-temperature furnace, first heat it to 200℃ and hold it for 1 hour, then continue heating it to 800℃ and hold it for 0.5 hours, then fill it with argon gas and continue heating it to 1950℃ and hold it for 5 hours, then cool it to room temperature to obtain a graphite device with a composite tantalum carbide coating on its surface.

[0111] Comparative Example 3

[0112] Step 1: Mix 6.7wt% PVA adhesive and the remaining tantalum carbide by mass fraction, add pure water at a solid-liquid ratio of 3g / mL, and ball mill for 2 hours to obtain a composite slurry.

[0113] Step 2: Apply composite slurry to the surface of the graphite device by brushing, dividing it into 8 brushings, and baking it at 150℃ for 10 minutes after each brushing.

[0114] Step 3: Place the graphite device with composite slurry coating obtained in Step 2 into a vacuum high-temperature furnace, first heat it to 200℃ and hold it for 1 hour, then continue heating it to 800℃ and hold it for 0.5 hours, then fill it with argon gas and continue heating it to 1950℃ and hold it for 5 hours, then cool it to room temperature to obtain a graphite device with a composite tantalum carbide coating on its surface.

[0115] <Experimental Example>

[0116] Samples: Examples 1-6, Comparative Examples 1-3

[0117] (1) The coating structure and morphology of the samples prepared in Examples 1-6 and Comparative Examples 1-3 were measured and recorded in Table 1 below:

[0118] Table 1. Composite coating structure and morphology of different samples

[0119]

[0120] Based on the structure and morphology of the composite layers of different samples in Table 1 above, and combined with the sample coating diagram of Example 1, it can be found that when preparing graphite device surface coatings of the same thickness, even if the sintering temperature of Examples 1 to 6 is lower than that of conventional sintering, the composite tantalum carbide coatings prepared by them have higher surface smoothness and can obtain graphite device surface composite tantalum carbide coatings with better morphology.

[0121] (2) Coating adhesion thermal shock test

[0122] Graphite device samples with tantalum carbide coatings on the surface, prepared in Examples 1-6 and Comparative Examples 1-3 respectively, were placed in a high-temperature vacuum furnace and heated to 2000°C within 5 minutes, then cooled to below 100°C. The heating and cooling process was repeated 3 times, and the damage to the coating on the surface of the graphite device was recorded. The graphite device samples were then placed in a liquid nitrogen container from room temperature and left to stand for 1 minute. After being removed, they were left to stand at room temperature for 1 minute. The standing process was repeated 3 times, and the damage to the coating on the surface of the graphite device was recorded.

[0123] Among them, the bonding strength resistance to rapid heating impact level refers to the number of times that the sample can remain unbroken when it is placed in a temperature difference of 2000℃ and room temperature alternately. "A" means more than 100 times, "B" means more than 50 times and less than 100 times, and "C" means less than 50 times.

[0124] The binding strength resistance to extreme cold shock rating refers to the number of times a sample can remain intact after being placed in a liquid nitrogen container and then in a temperature difference of room temperature, alternating between the two. "A" means it can withstand 10 or more extreme cold shocks, "B" means it can withstand 5-10 extreme cold shocks, and "C" means it can withstand less than 5 extreme cold shocks.

[0125] The above experimental results are summarized and recorded in Table 2 below:

[0126] Table 2. Damage to the coatings of different graphite device samples under different conditions.

[0127]

[0128]

[0129] As can be seen from the test results in Table 2 above, the graphite device samples of Examples 1 to 6 are all better able to maintain the integrity and effectiveness of the coating under the action of rapid heating shock and extreme cold shock, and can withstand more thermal shocks and cold shocks, indicating that the bonding force between the coating and the graphite substrate is stronger.

[0130] (3) Bonding force test

[0131] The coating adhesion and wear resistance are tested by the scratching method. The principle is to scratch the coating surface with a certain pressure and speed, and then observe whether there is peeling on the sample surface.

[0132] like Figure 1 This is a photograph of the surface morphology of the graphite device sample in Example 1 after scratching. Figure 2 This is an image showing the surface morphology of the graphite device sample in Comparative Example 1 after scratching. Figure 3 The image shows the surface morphology of the graphite device sample in Comparative Example 2 after scratching. Observation revealed that the surface smoothness of the graphite device sample in Example 1 was significantly higher than that of the graphite device samples in Comparative Example 1 and Comparative Example 2 after scratching.

[0133] Furthermore, based on whether there was irregular coating peeling off the scratched area, it was divided into two levels: Level A: no peeling, no scratches; Level B: peeling, scratches. The test results are summarized in Table 3 below:

[0134] Table 3. Degradation of tantalum carbide coating after scratching different graphite device samples.

[0135]

[0136]

[0137] As can be seen from the test results in Table 3 above, the graphite devices in Examples 1 to 6 still maintain good durability after being treated with scratching, while the graphite devices in Comparative Examples 1 to 3 show a significant decrease in bonding strength and wear resistance.

[0138] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A composite tantalum carbide coating on the surface of a graphite device, characterized in that, Along the surface of the graphite device outwards, the composite tantalum carbide coating includes a carbon layer, an intermediate tantalum carbide layer, and an outer tantalum carbide layer sequentially deposited. The intermediate tantalum carbide layer is obtained by reacting tantalum oxide, tantalum carbide and PVA adhesive; The outer layer of tantalum carbide, by mass fraction, is obtained by reacting 2-8% tantalum chloride, 0.3-0.8% chromium carbide, 2-10% PVA adhesive, 15-25% ethylene glycol and the balance tantalum carbide. The method for applying the composite tantalum carbide coating to the surface of the graphite device includes the following steps: S1. Carbon powder is mixed with adhesive and water, and sprayed to granulate to obtain spherical powder; the spherical powder is then plasma-sprayed onto the surface of a graphite substrate to form a carbon layer. S2. Tantalum oxide and tantalum carbide are mixed, PVA adhesive and water are added, and the mixture is granulated to obtain a mixed powder. The mixed powder is plasma sprayed onto the surface of the carbon layer to form an intermediate tantalum carbide layer. S3 mixes tantalum carbide, tantalum chloride, chromium carbide, PVA adhesive, ethylene glycol and water and ball-mills them to obtain a composite slurry; the composite slurry is coated onto the surface of the intermediate tantalum carbide layer in multiple layers to form the outer tantalum carbide layer; S4 The graphite substrate, after being processed in steps S1, S2 and S3, is placed in a heating furnace, preheated, and then heated in stages to 1920-1980℃ for reaction. After cooling, a graphite device with the composite tantalum carbide coating on its surface is obtained.

2. The tantalum carbide coating on the surface of the graphite device according to claim 1, characterized in that, The thickness of the carbon layer is ≤20μm.

3. The tantalum carbide coating on the surface of the graphite device according to claim 2, characterized in that, The carbon layer is formed by sintering carbon powder with a particle size of 0.08-0.12μm.

4. The tantalum carbide coating on the surface of the graphite device according to any one of claims 1 to 3, characterized in that, The thickness of the intermediate tantalum carbide layer is ≤50μm.

5. The tantalum carbide coating on the surface of the graphite device according to claim 4, characterized in that, The thickness of the tantalum carbide outer layer is 20-40 μm.

6. The tantalum carbide coating on the surface of the graphite device according to claim 1, characterized in that, In step S1, the particle size of the spherical powder is 0.1-2 μm.

7. The tantalum carbide coating on the surface of the graphite device according to claim 1 or 6, characterized in that, In step S3, the composite slurry is coated onto the surface of the intermediate tantalum carbide layer in 4-8 applications.

8. The tantalum carbide coating on the surface of the graphite device according to claim 7, characterized in that, After each coating is completed, bake at 130-160℃, cool to room temperature, and then apply the next coating.

9. The tantalum carbide coating on the surface of the graphite device according to claim 1 or 6, characterized in that, In step S4, the temperature is first kept at 200-220℃ for 0.8-1.2 hours, then raised to 780-820℃ and kept for 0.3-0.8 hours, and finally raised to 1920-1980℃ and kept for 4-6 hours.

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