A method for eliminating carbon adsorbed on the surface of carbide coatings

Abstract

This invention discloses a method for eliminating adsorbed carbon on the surface of a carbide coating. The method involves plasma-activating a substrate containing a defective carbide coating, then applying a repair slurry to the surface of the substrate to obtain a repair slurry layer. After drying, the sintering process yields the final product. This method can restore the surface C / M stoichiometry to 0.9-1.03 through a quantitative reaction between the applied slurry and the adsorbed carbon on the coating surface. Simultaneously, the coating becomes dense and defect-free. This method is particularly suitable for repairing coatings on graphite substrate thermal field components used in semiconductor crystal growth, and can significantly improve crystal growth quality.

Description

Technical Field

[0001] This invention belongs to the field of ceramic coating surface treatment technology, and specifically relates to a method for eliminating carbon adsorbed on the surface of carbide coatings. Background Technology

[0002] In thermal field components used for semiconductor single crystal growth, carbide ceramic coatings (such as SiC, TaC, and HfC) are widely used due to their high-temperature performance and chemical inertness. However, when carbide coatings are prepared using processes such as CVD, equipment contamination or incomplete decomposition of process gases can lead to changes in carbon potential in the thermal field, easily forming non-stoichiometric adsorbed carbon (such as free carbon) on the coating surface. This adsorbed carbon results in uneven emissivity on the coating surface, which in turn affects the temperature gradient distribution at the crystal growth interface and increases crystal defects. Traditional high-temperature annealing or mechanical polishing suffers from problems such as grain coarsening and brittle damage.

[0003] Therefore, there is an urgent need to develop a surface treatment method that can restore the stoichiometry of carbide coatings while maintaining the integrity of the coating. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a method for eliminating adsorbed carbon on the surface of carbide coatings. This method can quantitatively react with the adsorbed carbon on the coating surface through the application of a slurry, restoring the surface C / M (M=Si, Ta, Hf, etc.) stoichiometric ratio to 0.9-1.03. Simultaneously, the coating becomes dense and defect-free. This method is particularly suitable for coating repair of graphite-based thermal field components used in semiconductor crystal growth, and can significantly improve crystal growth quality.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] The present invention provides a method for eliminating carbon adsorbed on the surface of a carbide coating. The method involves plasma activation treatment of a substrate containing a defective carbide coating, followed by coating a repair slurry onto the surface of the substrate containing the defective coating to obtain a repair slurry layer, which is then dried and sintered to obtain the final product.

[0007] The repair slurry, by mass percentage, comprises the following: 60-70 wt% carbide powder, 1-2 wt% oxide powder, 0.5-1.5 wt% binder, 0.5-1.5 wt% dispersant, 1-3 wt% sintering aid, 0.1-0.3 wt% pH adjuster, with the balance being a composite solvent;

[0008] The carbides in the carbide powder are the same as those in the defective carbide coating;

[0009] The carbides obtained by thermal reduction reaction of oxides in the oxide powder with carbon are the same as those in the defective carbide coating.

[0010] The adhesive is selected from at least one of PVB and PVA;

[0011] The dispersant is selected from at least one of Tween-80 and BYK-306;

[0012] The sintering aid is selected from at least one of Co and Ni;

[0013] The composite solvent is selected from at least two of butanediol, ethanol, and benzyl alcohol;

[0014] The thickness of the repair slurry layer is 15-25 μm.

[0015] The preparation method of this invention first involves plasma treatment of the substrate containing a defective carbide coating. This process imparts polar groups to the surface of the substrate, enhancing its wettability with the repair slurry and making it easier for oxides to adsorb carbon. This increases the synergistic effect between surface activation and the reaction of the repair slurry. During sintering, the oxides in the repair slurry not only preferentially react with the adsorbed carbon in situ to form carbides, which then fill the surface defects of the original coating through epitaxial growth, but also the unreacted trace oxides from the heat treatment of the new coating are uniformly distributed at the grain boundaries. Their continuous reaction with residual carbon inhibits the re-adsorption of carbon, while the added carbides compensate for the cracking caused by the volume shrinkage after oxide reduction. The synergistic effect of these two factors ensures the integrity of the coating. Simultaneously, during the sintering process, the sintering aid of this invention... Because the eutectic temperature of the binder with the carbide (e.g., the eutectic point of Co-TiC is 1280℃) is 300-500℃ lower than the sintering temperature of pure carbide, it forms a liquid phase during sintering to promote particle rearrangement, inhibit abnormal grain growth in the carbide coating, and ensure that the performance of the original coating is not affected. The added binder can form a three-dimensional network skeleton at low temperature. During pyrolysis, it can not only form controllable nanopores (pore size 20-50nm) to provide an escape channel for CO gas generated by the subsequent carbothermic reduction reaction, but also react with carbon and oxides to generate nano carbides (e.g., SiO2+C→SiC), which further fills the micro-defects in the coating, thereby restoring the surface C / M (M=Si, Ta, Hf, etc.) stoichiometric ratio to 0.9-1.03, while the coating is dense and defect-free.

[0016] Of course, the uniform dispersion of carbide and oxide particles in the slurry is also crucial to the aforementioned sintering effect. Therefore, firstly, in this invention, at least one of Tween-80 and BYK-306 is selected as a dispersant. The dispersant can ensure the uniform dispersion of carbide and oxide particles through a stabilizing mechanism. When Tween-80 is used as a dispersant in an organic slurry system, its hydrophobic end is an oleic acid long chain, which can be physically adsorbed onto the surface of carbides and oxides after forming coordination bonds. The hydrophilic PEO chain extends into the solvent to form steric hindrance, thereby achieving uniform particle dispersion. Secondly, a composite solvent is used to achieve good compatibility with the dispersant and binder, thus ensuring the uniform dispersion of the carbide and oxide particles. Effective adsorption on the surface of the material ensures uniform dispersion of particles without agglomeration. The binder is uniformly dispersed to form a network skeleton, resulting in orderly accumulation of particles in the obtained green body. Moreover, the composite flux of this invention uses a combination of high-boiling-point and low-boiling-point flux to prevent excessively rapid volatilization and cracking during drying. Thirdly, controlling the distribution ratio of each component in the slurry within the range of this invention is also key to ensuring uniform dispersion of the two types of carbide and oxide particles. Through the synergistic effect of each component, when the particles are uniformly dispersed without agglomeration, they are then uniformly covered on the surface of the defective carbide coating by coating method. After slow drying, a green body with a high packing density is obtained. Finally, the uniformly dispersed particles in the green body, combined with low-temperature sintering aids, shorten the diffusion distance during heat treatment and promote densification dominated by grain boundary diffusion. If the proportions of each group are not within the scope of this invention, it will cause the particles to agglomerate or be insufficiently dispersed. During heat treatment, the oxides cannot play a full role, and a small amount of adsorbed carbon will still exist on the surface. In addition, although the main purpose of adding oxides is to remove adsorbed carbon through carbothermic reduction, the crystal structure changes after the phase transition, resulting in smaller interatomic spacing and thus volume shrinkage. As the amount of oxides added increases, more oxides are reduced to carbides, which intensifies the volume shrinkage. Therefore, only when an appropriate amount of oxides is added can the carbides compensate for the cracking caused by the volume shrinkage after oxide reduction and obtain a dense and defect-free coating.

[0017] Furthermore, in this invention, controlling the thickness of the repair slurry layer within the aforementioned range is essential to better restore the surface C / M stoichiometry and ensure a dense, defect-free coating. If the coating is too thin, the adsorbed carbon on the surface cannot be completely removed, and the stoichiometry of the coating surface cannot be restored during heat treatment. If the repair coating is too thick, it may hinder the escape of gases (such as CO), leading to increased internal porosity or unreacted oxide residues. The repair layer may exhibit minor defects that affect its performance.

[0018] In a preferred embodiment, the carbide in the substrate containing the defective carbide coating is selected from one of SiC, TaC, and HfC.

[0019] In a preferred embodiment, the substrate with the defective carbide coating is first subjected to ultrasonic cleaning with ethanol for 5-10 minutes, then ultrasonic cleaning with deionized water for 5-10 minutes, and then dried in an oven at 80-120℃ for 60-100 minutes. Finally, the dried substrate with the defective carbide coating is subjected to plasma activation treatment.

[0020] In a preferred embodiment, the plasma activation treatment is carried out in an oxygen atmosphere or an argon atmosphere, the power of the plasma activation treatment is 200-400W, and the time of the plasma activation treatment is 1-5min.

[0021] Experiments have shown that plasma activation treatment can acquire polar groups on the substrate surface of defective carbide coatings, thereby enhancing the wettability of the substrate surface of defective carbide coatings with the slurry, making it easier for oxides to contact and adsorb carbon, and promoting the complete reaction of carbon.

[0022] In a preferred embodiment, the particle size D50 of the carbide powder is ≤1.5μm, and the particle size D50 of the oxide powder is ≤1.5μm.

[0023] In this invention, the carbides in the carbide powder are the same as the carbides in the defective carbide coating (e.g., TaC powder is used to repair defective TaC coatings).

[0024] In a preferred embodiment, the adhesive is PVB.

[0025] In a preferred embodiment, the dispersant is Tween-80.

[0026] In a preferred embodiment, the sintering aid is Co.

[0027] In a preferred embodiment, the pH adjuster is selected from at least one of TMAH (tetramethylammonium hydroxide), ammonia, and citric acid, with ammonia being the most preferred.

[0028] In this invention, pH control can promote the effective adsorption of dispersant on the particle surface through the synergistic effect of two stabilization mechanisms: the double electric layer and the steric hindrance effect. This fully utilizes the role of the dispersant. When the dispersant is Tween-80, its ester bond hydrolysis is accelerated in a weakly alkaline environment (pH≈8), exposing more -COOH groups to enhance adsorption on the particle surface and further enhance the role of the dispersant.

[0029] In a preferred embodiment, the process of obtaining the repair slurry is as follows: carbide powder, oxide powder, sintering aid, composite solvent, and dispersant are mixed according to the design ratio and placed in a ball mill. The mixture is first ball-milled at a speed of 400-600 rpm for 2-3 hours, then a binder is added and the mixture is ball-milled at a speed of 80-120 rpm for 0.5-1 hours. Finally, a pH adjuster is added to adjust the pH to obtain the final product.

[0030] In the slurry preparation process, the present invention first adds carbides, oxides, sintering aids, solvents and dispersants in sequence and then performs high-speed ball milling. Finally, the binder is added and ball milled at low speed to prevent the binder and dispersant from competing for adsorption on the powder surface and to ensure that each component plays its full role.

[0031] In a further preferred embodiment, the ball milling process uses ball jars and balls made of silicon nitride or tungsten carbide.

[0032] In a preferred embodiment, the solid particles in the repair slurry have a particle size D50 of 0.6-1 μm, a viscosity of 100-150 mPa·s, and a pH of 5-10, preferably 7-5-8.5.

[0033] By controlling the conditions of the repair slurry within the above range, the final repair effect is optimal. If the solid particle size is too large, the slurry will be unstable due to the weight of the particles and will easily settle. If the particle size is too small, the specific surface area will increase and the slurry will be too thick, which is not conducive to the subsequent coating implementation.

[0034] In a preferred embodiment, the coating method is one of spraying, brushing, or dipping. In this invention, different coating methods can be selected for different structures, as long as the uniformity of the coating thickness is ensured.

[0035] In a preferred embodiment, the coating method is spraying. During spraying, the nozzle diameter is controlled to be 0.5-0.8 mm, the compressed air pressure to be 0.2-0.6 MPa, the spraying distance to be 15-25 cm, the spray gun moving speed to be 50-200 mm / s, and the spray gun angle to be 70-90°. 90° means the spray gun angle is perpendicular to the surface to be sprayed.

[0036] In a preferred embodiment, the drying process is as follows: first, the temperature is raised to 40-60℃ and held for 2-4 hours; then, the temperature is raised to 80-100℃ at a rate of 5-10℃ / min and held for 3-4 hours; finally, the temperature is raised to 120-150℃ at a rate of 1-3℃ / min and held for 3-6 hours.

[0037] In this invention, a segmented drying process can be used to gradually remove solvents with different boiling points, preventing excessively rapid evaporation from causing stress concentration in the green body and resulting in cracks.

[0038] In a preferred embodiment, the sintering is carried out under a protective atmosphere, and the sintering process is as follows: the temperature is increased to 250-350℃ at a heating rate of 5-7℃ / min and held for 0.5-1h; then the temperature is increased to 350-450℃ at a heating rate of 5-7℃ / min and held for 1-2h; then the temperature is increased to 1200-1400℃ at a heating rate of 6-10℃ / min and held for 2-3h; finally, the temperature is increased to 1600-1800℃ at a heating rate of 5-7℃ / min and held for 3-5h, with a vacuum degree of 5-7mbar.

[0039] In this invention, a slurry with uniformly dispersed particles and no agglomeration is obtained through the synergistic effect of the various components in the repair slurry. After being uniformly coated on the part to be repaired, a coating green body with a certain thickness and no defects such as cracks or pores is obtained by combining a gradient drying process. Then, through the above-mentioned sintering process, the surface C / M (M=Si, Ta, Hf, etc.) stoichiometric ratio is finally restored to 0.9-1.03, and the coating is dense and defect-free. During the above-mentioned sintering heat treatment process, polymers such as binders and dispersants are slowly removed in a gradient at low temperature, forming controllable nanopores. As the temperature rises, the uniformly dispersed oxides preferentially react with adsorbed carbon in situ to generate carbides, which fill the surface defects of the original coating through epitaxial growth. While the reaction is underway, the re-adsorption of adsorbed carbon is inhibited. With the formation of a liquid phase by uniformly distributed low-temperature sintering aids, the diffusion distance between carbide particles is shortened, promoting densification dominated by grain boundary diffusion.

[0040] Experiments have shown that after the polymers such as binders and dispersants are slowly removed in the low-temperature gradient insulation, it is necessary to further insulate at 1200-1400℃ and then raise the temperature to the highest temperature in order to achieve the highest coating density. This is because when the temperature is in the range of 1200-1400℃, the liquid phase fills the gaps between particles and enhances the migration of matter through capillary forces, thus promoting densification. When the temperature is outside this range, diffusion is not conducive and ultimately affects densification.

[0041] In a further preferred embodiment, the protective atmosphere is Ar gas.

[0042] Principles and advantages

[0043] The method of this invention first involves plasma treatment of the substrate containing defective carbide coatings, thereby acquiring polar groups on the surface of the substrate to enhance its wettability with the repair slurry. This makes it easier for oxides to contact and adsorb carbon, increasing the synergistic effect of surface activation and the reaction of the repair slurry. During sintering, the oxides in the repair slurry not only preferentially react with the adsorbed carbon in situ to generate carbides, which then fill the surface defects of the original coating through epitaxial growth, but also the unreacted trace oxides from the heat treatment of the new coating are uniformly distributed at the grain boundaries. Their continuous reaction with residual carbon can inhibit the re-adsorption of carbon, while the added carbides can compensate for the cracking caused by the volume shrinkage after oxide reduction. The synergistic effect of these two factors ensures the integrity of the coating and avoids the degradation of the substrate coating performance. Simultaneously, during the sintering process, this invention... The sintering aids have a eutectic temperature with the carbides (e.g., the eutectic point of Co-TiC is 1280℃) that is 300-500℃ lower than the sintering temperature of pure carbides. Therefore, during the sintering process, they form a liquid phase to promote particle rearrangement, inhibit abnormal growth of carbide coating grains, and ensure that the performance of the original coating is not affected. The added binder can form a three-dimensional network skeleton at low temperature. During pyrolysis, it can not only form controllable nanopores (pore size 20-50nm) to provide an escape channel for CO gas generated by the subsequent carbothermic reduction reaction, but also react with carbon and oxides to generate nano carbides (e.g., SiO2+C→SiC), which further fills the micro-defects of the coating, thereby restoring the surface C / M (M=Si, Ta, Hf, etc.) stoichiometric ratio to 0.9-1.03, while the coating is dense and defect-free.

[0044] The method provided by this invention is simple and low in cost, and is particularly suitable for surface repair of large-sized and complex-shaped parts. By quantitatively reacting the slurry with the adsorbed carbon on the coating surface, the surface C / M (M=Si, Ta, Hf, etc.) stoichiometric ratio is restored to 0.9-1.03, while the coating is dense and defect-free. Attached Figure Description

[0045] Figure 1 This is a process flow diagram of the present invention.

[0046] Figure 2 These are SEM comparison images of tantalum carbide coating before and after treatment in Example 1, wherein... Figure 2 (a) is a SEM image of the defective tantalum carbide coating before treatment. Figure 2 (b) is a SEM image of the tantalum carbide coating obtained after treatment in Example 1. Figure 2 In (a), 1 is the marker point of the first energy spectrum (EDS). Figure 2 In (b), 2 is the marker point of the second energy spectrum (EDS).

[0047] Figure 3 These are SEM images of different locations on the surface of the tantalum carbide coating in Comparative Example 1. Figure 3 (a) Figure 3 (b) SEM images of different locations on the surface of the tantalum carbide coating in Comparative Example 1 after surface treatment. Figure 3 In (b), 3 is the marker point of the third energy spectrum (EDS) and 4 is the marker point of the fourth energy spectrum (EDS). Detailed Implementation

[0048] Example 1

[0049] This embodiment provides a method for eliminating carbon adsorbed on the surface of a carbide coating, and the specific repair process is as follows:

[0050] Step S1: A 50×50×10mm tantalum carbide coated part (graphite substrate with defective tantalum carbide coating) is sequentially ultrasonically cleaned with ethanol and deionized water for 8 minutes each. Then, the coated part is placed in an oven and dried at 100℃ for 100 minutes to ensure no moisture residue remains on the surface. The coated part is then subjected to plasma activation treatment in an oxygen atmosphere at a power of 200W for 5 minutes.

[0051] Step S2: 100g TaC powder (particle size D50≤1.5μm), 2.85g Ta2O5 (particle size D50≤1.5μm), 2g Co powder, 6.2ml butanediol, 32ml ethanol, 4.8ml benzyl alcohol, and 1.4g Tween-80 are sequentially added to a silicon nitride ball mill jar. The grinding balls are silicon nitride, the ball-to-particle ratio is 2:1, the rotation speed is 400 rpm, and the ball milling time is 3 hours. Then, 1.1g PVB is added to the mixed suspension, the rotation speed is 100 rpm, and the ball milling time is 1 hour. Finally, 0.3g ammonia water is added and mixed evenly to obtain the repair slurry.

[0052] Step S3: The repair slurry prepared in S2 is uniformly sprayed onto the surface of the tantalum carbide coated part. The spraying parameters are: nozzle 0.5mm, air pressure 0.4 MPa, spray distance 18 cm, spray gun moving speed 150mm / s, spray gun angle 90° (perpendicular to the surface to be sprayed), and spray thickness 15-18μm.

[0053] Step S4: Dry the sprayed part prepared in S3 according to the following process: keep it at 45℃ for 2 hours, then raise the temperature to 100℃ at 5℃ / min and keep it at 4 hours, and then raise the temperature to 150℃ at 3℃ / min and keep it at 5 hours.

[0054] Step S5: Under an Ar atmosphere, heat to 250℃ at 5℃ / min and hold for 1 hour, then heat to 350℃ at 5℃ / min and hold for 2 hours, then heat to 1200℃ at 8℃ / min and hold for 2 hours, then heat to 1800℃ at 6℃ / min and hold for 4 hours, with a vacuum degree of 5-7 mbar; then cool to room temperature with the furnace to obtain the final product.

[0055] Testing revealed that the solid particles in the prepared repair slurry had a particle size D50 of 0.72 μm, a viscosity of 122 mPa·s, a pH of 8.1, and a final coating thickness of 5-7 μm after heat treatment. According to... Figure 1 The image shown is a SEM image of tantalum carbide coating before and after treatment in Example 1. Figure 2 (b) is a SEM image of the tantalum carbide coating obtained after treatment in Example 1. Figure 2 (b) It can be seen that the adsorbed carbon was almost completely removed after the coating surface was repaired, and the coating completely covered the surface without any cracks or defects. Figure 2 (a) The first energy spectrum (EDS) marker point 1 and Figure 2 (b) The EDS analysis of the second energy dispersive spectroscopy (EDS) marker 2 is shown in Table 1. The C / TaC atomic ratio on the coating surface decreased from 7.84 to 0.96, thus restoring the surface stoichiometry.

[0056]

[0057] Example 2

[0058] This embodiment provides a method for eliminating carbon adsorbed on the surface of a carbide coating, and the specific repair process is as follows:

[0059] Step S1: The tantalum carbide coated part with dimensions of 50×50×10mm is ultrasonically cleaned with ethanol and deionized water in sequence, and the ultrasonic cleaning time is 10min for each time; then the coated part is placed in an oven at 120℃ and dried for 100min to ensure that there is no moisture residue on the surface; the coated part is then subjected to plasma activation treatment in an oxygen atmosphere at a power of 400W for a treatment time of 3min.

[0060] Step S2: 100g TaC powder (particle size D50≤1.5μm), 2.65g Ta2O5 (particle size D50≤1.5μm), 2.2g Co powder, 7.2ml butanediol, 33.6ml ethanol, 5.8ml benzyl alcohol, and 1.2g Tween-80 are sequentially added to a silicon nitride ball mill jar. The grinding balls are silicon nitride, the ball-to-particle ratio is 2:1, the rotation speed is 400 rpm, and the ball milling time is 2.5 hours. Then, 1.2g PVB is added to the mixed suspension, the rotation speed is 100 rpm, and the ball milling time is 1 hour. Finally, 0.2g ammonia water is added and mixed evenly to obtain the repair slurry.

[0061] Step S3: The repair slurry prepared in S2 is uniformly sprayed onto the surface of the tantalum carbide coated part. The spraying parameters are: nozzle 0.5mm, air pressure 0.4 MPa, spray distance 18 cm, spray gun moving speed 150mm / s, spray gun angle 90° (perpendicular to the surface to be sprayed), and spray thickness 15-18μm.

[0062] Step S4: Dry the sprayed part prepared in S3 according to the following process: keep it at 45℃ for 2 hours, then raise the temperature to 100℃ at 5℃ / min and keep it at 4 hours, and then raise the temperature to 150℃ at 3℃ / min and keep it at 6 hours.

[0063] Step S5: Under an Ar atmosphere, heat to 250℃ at 5℃ / min and hold for 1 hour, then heat to 350℃ at 5℃ / min and hold for 2 hours, then heat to 1200℃ at 8℃ / min and hold for 2 hours, then heat to 1750℃ at 6℃ / min and hold for 4.5 hours, with a vacuum degree of 5-7 mbar; then cool to room temperature with the furnace to obtain the final product.

[0064] Testing revealed that the solid particles in the prepared repair slurry had a particle size D50 of 0.85 μm, a viscosity of 145 mPa·s, and a pH of 7.8. After final heat treatment, the coating thickness was 5-7 μm. The coating in Example 2 had a surface morphology essentially the same as that in Example 1. After repair, almost all adsorbed carbon was removed from the coating surface, and the coating completely covered the surface without any cracks or defects. The C / TaC atomic ratio on the coating surface decreased from 4.65 to 0.91.

[0065] Example 3

[0066] This embodiment provides a method for eliminating carbon adsorbed on the surface of a carbide coating, and the specific repair process is as follows:

[0067] Step S1: The tantalum carbide coated part with dimensions of 50×50×10mm is ultrasonically cleaned sequentially with ethanol and deionized water for 10 minutes each. Next, the coated part is placed in an oven at 120℃ and dried for 100 minutes to ensure no moisture residue remains on the surface. Then, the coated part is subjected to plasma activation treatment in an oxygen atmosphere at a power of 300W for 5 minutes.

[0068] Step S2: 100g TaC powder (particle size D50≤1.5μm), 2.77g Ta2O5 (particle size D50≤1.5μm), 2.4g Co powder, 5.3ml butanediol, 30.2ml ethanol, 4.1ml benzyl alcohol, and 1.3g Tween-80 are sequentially added to a silicon nitride ball mill jar. The grinding balls are silicon nitride, the ball-to-particle ratio is 2:1, the rotation speed is 400 rpm, and the ball milling time is 3 hours. Then, 1.2g PVB is added to the mixed suspension, the rotation speed is 100 rpm, and the ball milling time is 1 hour. Finally, 0.2g ammonia water is added and mixed evenly to obtain the repair slurry.

[0069] Step S3: The repair slurry prepared in S2 is uniformly sprayed onto the surface of the tantalum carbide coated part. The spraying parameters are: nozzle 0.5mm, air pressure 0.4 MPa, spray distance 18 cm, spray gun moving speed 150mm / s, spray gun angle 90° (perpendicular to the surface to be sprayed), and spray thickness 23-25μm.

[0070] Step S4: Dry the sprayed part prepared in S3 according to the following process: keep it at 45℃ for 2 hours, then raise the temperature to 100℃ at 5℃ / min and keep it at 4 hours, and then raise the temperature to 150℃ at 3℃ / min and keep it at 5 hours.

[0071] Step S5: Under an Ar atmosphere, heat to 250℃ at 5℃ / min and hold for 1 hour, then heat to 350℃ at 5℃ / min and hold for 2 hours, then heat to 1200℃ at 8℃ / min and hold for 2 hours, then heat to 1800℃ at 6℃ / min and hold for 4 hours, with a vacuum of 5-7 mbar. Then cool to room temperature with the furnace to obtain the final product.

[0072] Testing revealed that the solid particles of the prepared repair slurry had a particle size D50 of 0.77 μm, a viscosity of 132 mPa·s, a pH of 8.2, and a coating thickness of 8-10 μm after final heat treatment. The surface morphology of the coating in Example 3 was basically the same as that in Example 1. After repair, almost all adsorbed carbon was removed from the coating surface, and the coating completely covered the surface without any cracks or defects. The C / Ta atomic ratio on the coating surface decreased from 6.71 to 0.92.

[0073] Comparative Example 1

[0074] This comparative example is identical to Example 1 under all other conditions except that Ta2O5 powder is not added during the slurry preparation process in step S2.

[0075] The prepared tantalum carbide slurry was tested and found to have a particle size D50 of 0.70 μm, a viscosity of 145 mPa·s, a pH of 8.0, and a coating thickness of 5-7 μm after final heat treatment. The ceramic material obtained in Comparative Example 1 is as follows... Figure 3 The image shown is an SEM image of different locations after tantalum carbide coating surface treatment. Figure 3 (a) Figure 3 In (b), dark gray areas are visible, indicating that adsorbed carbon still exists locally on the coating surface. Figure 3 EDS analysis was performed on the third energy dispersive spectroscopy (EDS) marker 3 and the fourth energy dispersive spectroscopy (EDS) marker 4 in (b). The results are shown in Table 2. The surface stoichiometry C / TaC = 0.9-1.03 was not achieved. This is because the absence of oxide powder will result in insufficient reaction of adsorbed carbon, and the re-adsorption of carbon cannot be further inhibited during heat treatment.

[0076]

[0077] Comparative Example 2

[0078] Comparative Example 2 is identical to Example 1 in all other conditions except that 0.8g of Ta2O5 powder is added during the slurry preparation process in step S2.

[0079] The prepared tantalum carbide slurry had a particle size D50 of 0.78 μm, a viscosity of 121 mPa·s, a pH of 8.1, and a final coating thickness of 5-7 μm after heat treatment. The surface morphology of the coating was basically consistent with that of Comparative Example 1. Adsorbed carbon was still present in some areas of the coating surface, and the surface stoichiometry (C / TaC = 0.9-1.05) was not achieved. This indicates that the addition of oxide powder undergoing carbothermic reduction during slurry preparation must be strictly performed according to the requirements of this invention. Adding tantalum pentoxide powder outside the above requirements cannot restore the surface stoichiometry of the coating.

[0080] Comparative Example 3

[0081] The conditions for this comparative example are exactly the same as those for Example 1, except that the coating thickness in step S3 is 35-40 μm.

[0082] Testing revealed that the final coating thickness after heat treatment was 18-22 μm. The coating surface exhibited a small number of defects such as microcracks and pinholes, and locally adsorbed carbon remained, resulting in a surface stoichiometry of C / TaC = 0.9-1.05. Excessive coating thickness during repair may impede gas escape (such as CO), leading to increased internal porosity or residual unreacted oxides, resulting in minor defects in the repair layer and affecting performance.

Claims

1. A method for eliminating carbon adsorbed on the surface of a carbide coating, characterized in that: The substrate containing the defective carbide coating is subjected to plasma activation treatment, and then the repair slurry is coated on the surface of the substrate containing the defective coating to obtain the repair slurry layer. After drying, it is sintered to obtain the final product. The repair slurry, by mass percentage, comprises the following: 60-70 wt% carbide powder, 1-2 wt% oxide powder, 0.5-1.5 wt% binder, 0.5-1.5 wt% dispersant, 1-3 wt% sintering aid, 0.1-0.3 wt% pH adjuster, with the balance being a composite solvent; The carbides in the carbide powder are the same as those in the defective carbide coating; The carbides obtained by thermal reduction reaction of oxides in the oxide powder with carbon are the same as those in the defective carbide coating. The adhesive is selected from at least one of PVB and PVA; The dispersant is selected from at least one of Tween-80 and BYK-306; The sintering aid is selected from at least one of Co and Ni; The composite solvent is selected from at least two of butanediol, ethanol, and benzyl alcohol; The thickness of the repair slurry layer is 15-25 μm.

2. The method for eliminating carbon adsorbed on the surface of a carbide coating according to claim 1, characterized in that: First, the substrate with defective carbide coating is ultrasonically cleaned with ethanol for 5-10 minutes and ultrasonically cleaned with deionized water for 5-10 minutes. Then, it is placed in an oven and dried at 80-120℃ for 60-100 minutes. Finally, the dried substrate with defective carbide coating is subjected to plasma activation treatment.

3. The method for eliminating carbon adsorbed on the surface of a carbide coating according to claim 1, characterized in that: The plasma activation treatment is carried out in an oxygen atmosphere or an argon atmosphere, the power of the plasma activation treatment is 200-400W, and the time of the plasma activation treatment is 1-5min.

4. The method for eliminating carbon adsorbed on the surface of a carbide coating according to claim 1, characterized in that: The particle size D50 of the carbide powder is ≤1.5μm, and the particle size D50 of the oxide powder is ≤1.5μm.

5. The method for eliminating carbon adsorbed on the surface of a carbide coating according to claim 1, characterized in that: The process of obtaining the repair slurry is as follows: carbide powder, oxide powder, sintering aid, composite solvent and dispersant are prepared according to the design ratio and placed in a ball mill. First, the ball mill is run at a speed of 400-600 rpm for 2-3 hours. Then, the binder is added and the ball mill is run at a speed of 80-120 rpm for 0.5-1 hours. Finally, the pH adjuster is added to adjust the pH to obtain the slurry. The ball milling process uses ball jars and balls made of silicon nitride or tungsten carbide.

6. The method for eliminating carbon adsorbed on the surface of a carbide coating according to claim 1, characterized in that: The solid particles in the repair slurry have a particle size D50 of 0.6-1 μm, a viscosity of 100-150 mPa·s, and a pH of 5-10. The coating method is one of spraying, brushing, or dipping.

7. The method for eliminating carbon adsorbed on the surface of a carbide coating according to claim 6, characterized in that: The coating method is spraying. During spraying, the nozzle diameter is controlled to be 0.5-0.8mm, the compressed air pressure is 0.2-0.6Mpa, the spraying distance is 15-25cm, the spray gun moving speed is 50-200mm / s, and the spray gun angle is 70-90°.

8. The method for eliminating carbon adsorbed on the surface of a carbide coating according to claim 1, characterized in that: The drying process is as follows: first, heat the temperature to 40-60℃ and hold for 2-4 hours; then, heat the temperature to 80-100℃ at a rate of 5-10℃ / min and hold for 3-4 hours; finally, heat the temperature to 120-150℃ at a rate of 1-3℃ / min and hold for 3-6 hours.

9. The method for eliminating carbon adsorbed on the surface of a carbide coating according to claim 1, characterized in that: The sintering is carried out under a protective atmosphere. The sintering process is as follows: the temperature is increased to 250-300℃ at a heating rate of 5-7℃ / min and held for 0.5-1h; then the temperature is increased to 350-450℃ at a heating rate of 5-7℃ / min and held for 1-2h; then the temperature is increased to 1200-1400℃ at a heating rate of 6-10℃ / min and held for 2-3h; finally, the temperature is increased to 1600-1800℃ at a heating rate of 5-7℃ / min and held for 3-5h. The vacuum degree is 5-7mbar.

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