Effects of Furnace Pressure and Sample Position on Microstructure and Thermal Fatigue Resistance of CVD - SiC Coatings

The SiC coating prepared on graphite substrate can effectively solve the corrosion and powder loss problems of graphite material in environments with high temperature and corrosive gas. In this paper, a SiC coating was prepared on the surface of graphite substrate. The deposition process parameters were adjusted and optimized to realize rapid manufacturing of high - performance SiC coating with the aim of providing theoretical basis and technical support for SiC coating’ application on the surface of graphite substrate. An industrial - grade chemical vapor deposition equipment was employed to prepare the silicon carbide coating on the surface of graphite substrates using methyl trichlorosilane (MTS) and H2 as raw materials. The effects of furnace pressure and sample position on the microstructure and thermal fatigue resistance of the coating were studied by analysis and testing methods such as scanning electron microscopy, X - ray diffractometer and vacuum thermal cycling. Results showed that when the furnace pressure was 2.0 kPa, a high - purity silicon carbide coating with single grain growth orientation could be prepared. As the furnace pressure increased, the deposition rate and thermal fatigue resistance of the coating both showed a non - monotonic change of first rising, then falling and then rising again. When the furnace pressure was 2.0 kPa, the silicon carbide coating had the highest deposition rate and the best thermal fatigue resistance. The coatings prepared with different sample positions were all pure SiC coatings, and the closer the substrate suspension position to the air distribution plate, the faster the coating deposition rate was and the better thermal fatigue resistance the coating showed. When the furnace pressure was 2.0 kPa and the sample position was 300 mm, a SiC coating with good thermal fatigue resistance could be quickly prepared.