Coating structure for a CVD-SiC surface and coating method

Abstract

The present application relates to the field of coating preparation, in particular to a coating structure for CVD-SiC surface and a coating method, the coating structure comprises from inside to outside: graphite substrate; interface strengthening layer; silicon carbide coating. The present application combines a unique interface strengthening mechanism with an advanced deposition process to achieve the construction of a strong and tough, dense and highly matched protective coating on a complex substrate. Compared with the prior art, the method significantly improves the bonding strength, thermal shock resistance and environmental adaptability of the coating, effectively inhibits cracking and peeling, and at the same time ensures the uniformity and integrity of the coating. The technology has broad application prospects in the fields of high-performance thermal field components, semiconductor equipment and extreme environment protection.

Description

Technical Field

[0001] This invention relates to the field of coating preparation, and more particularly to a coating structure and coating method for CVD-SiC surfaces. Background Technology

[0002] Chemical vapor deposition silicon carbide (CVD-SiC) is a high-purity, dense SiC material deposited by chemical reaction of a vapor precursor on a high-temperature substrate surface. With its excellent high-temperature strength, extremely high thermal conductivity, outstanding wear and corrosion resistance, and good neutron irradiation stability, it has become an irreplaceable key basic material in cutting-edge technology fields such as semiconductor manufacturing equipment, hot-end components of next-generation aerospace engines, and nuclear reactor cladding materials.

[0003] However, the performance of CVD-SiC bulk materials still faces challenges under extreme service environments, such as high-temperature oxidation, molten salt corrosion, particle erosion, or plasma erosion.

[0004] In existing technologies, a single silicide coating or a simple bilayer structure is typically used to protect the CVD-SiC substrate. These methods mainly isolate corrosive media by providing a physical barrier. However, there is a significant difference in the coefficient of thermal expansion between CVD-SiC and commonly used coating materials. During intense thermal cycling, huge thermal stress is generated at the interface, which makes the coating prone to cracking or even peeling off from the substrate. In addition, coatings made of a single material cannot simultaneously meet the comprehensive requirements of corrosion resistance, erosion resistance and long-term stability. Furthermore, traditional coating preparation processes, such as atmospheric plasma spraying, may introduce pores and impurities into the coating and are difficult to achieve uniform coverage on complex shaped parts, thus limiting the overall performance and reliability of the coating.

[0005] Therefore, based on the relevant technologies mentioned above, there is an urgent need to develop a coating structure and coating method for CVD-SiC surfaces. Summary of the Invention

[0006] In view of this, the purpose of this invention is to propose a coating structure and coating method for CVD-SiC surfaces to solve the problems of weak adhesion, easy cracking, single performance and uneven coverage in the prior art.

[0007] To achieve the above objectives, the present invention provides a coating structure and coating method for CVD-SiC surfaces.

[0008] A coating structure for CVD-SiC surfaces, wherein the coating structure comprises, from the inside out:

[0009] Graphite substrate: It has open micropores formed inside after thermal cleaning;

[0010] Interface reinforcement layer: A silicon-carbon composite layer formed by liquid silicon penetrating into the micropores of graphite and the gaps in the graphite or SiC assembly;

[0011] Silicon carbide coating: A dense, continuous SiC layer formed on the interface reinforcement layer.

[0012] A coating method for a coating structure on a CVD-SiC surface, the coating method being as follows:

[0013] Step S1: Pre-treat the graphite substrate;

[0014] Step S2: Perform silicon liquid phase infiltration and interface strengthening;

[0015] Step S3: Perform chemical vapor deposition to form a silicon carbide coating;

[0016] Step S4: Perform high-temperature annealing and post-treatment.

[0017] Preferably, step S1 specifically includes the following steps:

[0018] Under an argon atmosphere, the graphite matrix is ​​placed in a sintering furnace and heated to 780-820℃ at a heating rate of 3-5℃ / min. The temperature is held for 80-120 minutes. After the holding period, the temperature is lowered to 20-30℃ before proceeding to the next step.

[0019] Preferably, step S2 specifically includes the following steps:

[0020] Under an argon atmosphere, the component treated in step S1 is heated to 1400-1500℃ at a heating rate of 6-10℃ / min. A silicon-containing gaseous precursor is introduced at a flow rate of 1000-2000 sccm, and the reaction chamber pressure is 8-10 kPa. The reaction is carried out for 20-40 min. The addition of the silicon-containing gaseous precursor is stopped, and the temperature is maintained for 100-120 min. After the temperature maintenance is completed, the process proceeds to the next step.

[0021] Preferably, the silicon-containing gaseous precursor is either silane or chlorosilane, and its volume concentration is 8%-10%.

[0022] Preferably, in step S2, the deposition and heat preservation process causes the workpiece to rotate at a constant speed of 10-20 rpm.

[0023] Preferably, step S3 specifically includes the following steps:

[0024] Adjust the system temperature to 1250-1350℃, introduce a methyltrichlorosilane mixture with hydrogen as the carrier gas into the reaction chamber, with a total gas flow rate of 3000-5000 sccm, a reaction chamber pressure of 1-10 kPa, and a deposition time of 8-10 h. After deposition is complete, proceed to the next step.

[0025] Preferably, the volume concentration of the methyltrichlorosilane is 1%-5%.

[0026] Preferably, step S4 specifically includes the following steps:

[0027] In an argon atmosphere, the coated part is heated to 1500-1700℃ at a rate of 3-8℃ / min and held at that temperature for 1-4 hours. After annealing, the part is cooled to 20-30℃ at a rate of 1-5℃ / min.

[0028] The beneficial effects of this invention are:

[0029] This invention provides a high-performance coating structure for CVD-SiC surfaces and its preparation method. By combining a unique interface strengthening mechanism with advanced deposition processes, this invention achieves the construction of a tough, dense, and highly substrate-compatible protective coating on complex substrates. Compared with existing technologies, this method significantly improves the coating's bonding strength, thermal shock resistance, and environmental adaptability, effectively suppressing cracking and peeling, while ensuring the coating's uniformity and integrity. This technology has broad application prospects in high-performance thermal field components, semiconductor equipment, and extreme environment protection. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0031] Example 1: Preparation of a coating structure for CVD-SiC surfaces

[0032] S1: Under an argon atmosphere, the graphite matrix assembled with SiC components is placed in a high-temperature sintering furnace and heated to 800°C at a rate of 5°C / min. The temperature is held for 100 min, and after the holding period, the temperature is cooled to 20°C for later use.

[0033] S2: Under an argon atmosphere, the part treated in S1 is placed in a CVD reaction chamber and heated to 1450℃ at a heating rate of 8℃ / min. Silane with a volume concentration of 9% is introduced, the pressure in the reaction chamber is maintained at 9kPa, the gas flow rate is 1500sccm, and the reaction is carried out for 30min. Then, the silane is stopped and the temperature is maintained for 110min. During this process, the workpiece is rotated at a uniform speed of 15rpm.

[0034] S3: Adjust the system temperature to 1300℃, introduce a methyltrichlorosilane mixture with hydrogen as the carrier gas into the reaction chamber, wherein the volume concentration of methyltrichlorosilane is 3%, the total gas flow rate is 4000 sccm, the reaction chamber pressure is 5 kPa, and the deposition time is 9 hours.

[0035] S4: In an argon atmosphere, the coated part is heated to 1600℃ at a rate of 5℃ / min and held at that temperature for 2 hours. After annealing, the part is cooled to 25℃ at a rate of 3℃ / min to obtain the coated structure.

[0036] Example 2: Preparation of a coating structure for CVD-SiC surfaces

[0037] S1: Under an argon atmosphere, the graphite matrix assembled with SiC components is placed in a high-temperature sintering furnace and heated to 780°C at a rate of 4°C / min. The temperature is held for 120 minutes. After the holding period, the temperature is lowered to 20°C for later use.

[0038] S2: Under an argon atmosphere, the part treated in S1 is placed in a CVD reaction chamber and heated to 1400℃ at a heating rate of 6℃ / min. Silane with a volume concentration of 8% is introduced, the pressure in the reaction chamber is maintained at 9kPa, the gas flow rate is 1000sccm, the reaction is carried out for 20min, the introduction of silane is stopped, and the temperature is maintained for 100min. During this process, the workpiece is rotated at a uniform speed of 10rpm.

[0039] S3: Adjust the system temperature to 1300℃, introduce a methyltrichlorosilane mixed gas with hydrogen as the carrier gas into the reaction chamber, wherein the volume concentration of methyltrichlorosilane is 1%, the total gas flow rate is 3000 sccm, the reaction chamber pressure is 1 kPa, and the deposition time is 8 hours.

[0040] S4: In an argon atmosphere, the coated part is heated to 1500℃ at a rate of 5℃ / min and held at that temperature for 1 hour. After annealing, the part is cooled to 25℃ at a rate of 5℃ / min to obtain the coated structure.

[0041] Example 3: Preparation of a coating structure for CVD-SiC surfaces

[0042] S1: Under an argon atmosphere, the graphite matrix assembled with SiC components is placed in a high-temperature sintering furnace and heated to 820°C at a rate of 5°C / min. The temperature is held for 80 minutes. After the holding period, the temperature is cooled to 30°C and set aside for later use.

[0043] S2: Under an argon atmosphere, the part treated in S1 is placed in a CVD reaction chamber and heated to 1500℃ at a heating rate of 10℃ / min. Silane with a volume concentration of 10% is introduced, the pressure in the reaction chamber is maintained at 10kPa, the gas flow rate is 1600sccm, the reaction is carried out for 40min, the introduction of silane is stopped, and the temperature is maintained for 120min. During this process, the workpiece is rotated at a uniform speed of 20rpm.

[0044] S3: Adjust the system temperature to 1350℃, introduce a methyltrichlorosilane mixed gas with hydrogen as the carrier gas into the reaction chamber, wherein the volume concentration of methyltrichlorosilane is 5%, the total gas flow rate is 4000 sccm, the reaction chamber pressure is 10 kPa, and the deposition time is 10 h.

[0045] S4: In an argon atmosphere, the coated part is heated to 1700℃ at a rate of 8℃ / min and held at that temperature for 4 hours. After annealing, the part is cooled to 30℃ at a rate of 5℃ / min to obtain the coated structure.

[0046] Comparative Example 1:

[0047] Compared with Example 1, this comparative example did not add silane in the preparation process of a coating structure for CVD-SiC surface. All other steps and parameters were the same, and will not be repeated in this comparative example. The final coating structure was obtained.

[0048] Comparative Example 2:

[0049] Compared with Example 1, this comparative example only replaces the CVD deposition process in step S3 with an atmospheric plasma spraying process. All other steps and parameters are the same, and will not be repeated here. The final coating structure is obtained.

[0050] Comparative Example 3:

[0051] This comparative example involves depositing a CVD-SiC coating directly on the surface of graphite / SiC assemblies from the same batch that have not undergone any surface treatment, using the process parameters S3 and S4 of Example 1.

[0052] Performance testing:

[0053] Coating adhesion strength test

[0054] The AG-IC100kN universal testing machine was used in accordance with the GB / T8642-2002 testing standard.

[0055] 1. Take the coating samples of Examples 1-3 and Comparative Examples 1-3 respectively, and bond them to the uncoated steel fixtures with E7 type high-strength epoxy resin adhesive. Heat to 25°C and cure for 24 hours to obtain the samples.

[0056] 2. Place the sample on a universal testing machine and apply a tensile rate of 1.0 mm / min until the coating peels or cohesive failure occurs. Record the maximum failure load (F).

[0057] 3. Combined with the strength calculation formula: A is the bonding area (approximately 3.14 cm²). 2 ).

[0058] Table 1. Test results of the bonding strength of the coatings in the examples and comparative examples.

[0059]

[0060] Thermal shock resistance test

[0061] The test method for thermal shock resistance of coatings was conducted using a box-type resistance furnace (SX-G17123).

[0062] 1. Take the coating samples of Examples 1-3 and Comparative Examples 1-3 respectively, place them in a resistance furnace, heat them to 1200±10℃, keep them at that temperature for 10 minutes, take them out after the holding time is over, put them into flowing deionized water at 25±5℃ for quenching, keep them for 30 seconds, take them out and blow them dry.

[0063] 2. Repeat the above steps and record the number of thermal cycles experienced when the coating first shows visible macroscopic cracks (length > 1 mm), peeling, or flaking.

[0064] Table 2. Thermal shock resistance test results of the examples and comparative examples.

[0065]

[0066] High-temperature antioxidant performance test

[0067] The KSL-1700X box furnace was used in accordance with the GB / T13303-1991 testing standard.

[0068] 1. Take the coating samples of Examples 1-3 and Comparative Examples 1-3, each with a mass of m0, place them in a corundum crucible, heat them to 1400±10℃, keep them at that temperature for 100h, take them out, cool them to room temperature, brush off the oxide scale, and weigh the final mass of the sample (m1).

[0069] 2. Formula for calculating the change in mass per unit area: A represents the area of ​​the coating sample.

[0070] Table 3 Performance test results of the examples and comparative examples

[0071]

[0072] Data Analysis:

[0073] As can be seen from Tables 1-3, the coating structure prepared in the embodiments of the present invention has higher bonding strength, better thermal shock resistance and better high-temperature oxidation resistance.

[0074] In contrast, Comparative Example 1, due to the absence of silicon liquid phase infiltration and interface strengthening treatment in step S2, has a bonding strength that is only about one-third of that of the Example, a significant reduction in the number of thermal shock cycles, and a significant increase in weight gain due to high-temperature oxidation. The fundamental reason is the lack of a silicon-carbon composite interface strengthening layer formed by the liquid silicon infiltration reaction, which makes it impossible to achieve a strong mechanical anchoring and chemical bonding between the coating and the graphite substrate. At the same time, interface defects become thermal stress concentration points and oxygen diffusion channels.

[0075] Comparative Example 2, by replacing the CVD deposition process in step S3 with atmospheric plasma spraying, resulted in a bonding strength that was higher than that of Comparative Example 1 but still much lower than that of the Example. Its thermal shock resistance was limited and its oxidation resistance was the worst. This is because the coating formed by plasma spraying has a layered structure and inherent pores, low cohesive strength and non-dense structure. It is easy for the layers to separate during thermal cycling and provides a fast path for oxidation and erosion.

[0076] Comparative Example 3 completely omits the interface treatment and strengthening steps of the present invention, and directly deposits the coating on the untreated substrate, resulting in extremely low bonding strength. It completely fails in the first thermal shock and cannot be effectively tested for oxidation resistance. The reason is that there is only a weak van der Waals force bond between the coating and the heterogeneous substrate, and there is no effective interlocking or chemical bonding mechanism. It is very easy to fail at the interface under thermal stress or usage environment.

[0077] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention is limited to these examples; within the framework of the invention, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of the different aspects of the invention as described above, which are not provided in detail for the sake of brevity.

[0078] This invention is intended to cover all such substitutions, modifications, and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A coating structure for CVD-SiC surfaces, characterized in that, The coating structure, from the inside out, is as follows: Graphite substrate: It has open micropores formed inside after thermal cleaning; Interface reinforcement layer: A silicon-carbon composite layer formed by liquid silicon penetrating into the micropores of graphite and the gaps in the graphite or SiC assembly; Silicon carbide coating: A dense, continuous SiC layer formed on the interface reinforcement layer.

2. The coating method for a coating structure on a CVD-SiC surface according to claim 1, characterized in that, The coating method is as follows: Step S1: Pre-treat the graphite substrate; Step S2: Perform silicon liquid phase infiltration and interface strengthening; Step S3: Perform chemical vapor deposition to form a silicon carbide coating; Step S4: Perform high-temperature annealing and post-treatment.

3. The coating method for a coating structure on a CVD-SiC surface according to claim 2, characterized in that, The specific steps of step S1 are as follows: Under an argon atmosphere, the graphite matrix is ​​placed in a sintering furnace and heated to 780-820℃ at a heating rate of 3-5℃ / min. The temperature is held for 80-120 minutes. After the holding period, the temperature is lowered to 20-30℃ before proceeding to the next step.

4. The coating method for a coating structure on a CVD-SiC surface according to claim 1, characterized in that, The specific steps of step S2 are as follows: Under an argon atmosphere, the component treated in step S1 is heated to 1400-1500℃ at a heating rate of 6-10℃ / min. A silicon-containing gaseous precursor is introduced at a flow rate of 1000-2000 sccm, and the reaction chamber pressure is 8-10 kPa. The reaction is carried out for 20-40 min. The addition of the silicon-containing gaseous precursor is stopped, and the temperature is maintained for 100-120 min. After the temperature maintenance is completed, the process proceeds to the next step.

5. The coating method for a coating structure on a CVD-SiC surface according to claim 4, characterized in that, The silicon-containing gaseous precursor is either silane or chlorosilane, with a volume concentration of 8%-10%.

6. The coating method for a coating structure on a CVD-SiC surface according to claim 4, characterized in that, The deposition and heat preservation process described in step S2 involves rotating the workpiece at a constant speed of 10-20 rpm.

7. The coating method for a coating structure on a CVD-SiC surface according to claim 1, characterized in that, The specific steps of step S3 are as follows: Adjust the system temperature to 1250-1350℃, introduce a methyltrichlorosilane mixture with hydrogen as the carrier gas into the reaction chamber, with a total gas flow rate of 3000-5000 sccm, a reaction chamber pressure of 1-10 kPa, and a deposition time of 8-10 h. After deposition is complete, proceed to the next step.

8. The coating method for a coating structure on a CVD-SiC surface according to claim 7, characterized in that, The volume concentration of the methyltrichlorosilane is 1%-5%.

9. A coating method for a coating structure on a CVD-SiC surface according to claim 1, characterized in that, The specific steps of step S4 are as follows: In an argon atmosphere, the coated part is heated to 1500-1700℃ at a rate of 3-8℃ / min and held at that temperature for 1-4 hours. After annealing, the part is cooled to 20-30℃ at a rate of 1-5℃ / min.

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