Oxidation resistant SiC coating for graphite materials

A dense functional gradient SiSiC coating with good oxidation resistance when applied to a graphite substrate has been developed using a novel process, in which large pores in the coating were eliminated by application of a primary coating, and pinholes were filled with free silicon. The mechanism for the formation of a continuous SiC coating on graphite was investigated experimentally and theoretically. Oxidation tests were conducted from 800°C to 1600°C for up to 1000 h. Samples of graphite with the SiSiC coating were found to be totally intact after oxidizing for 1000 h together with 100 thermal cycles at 1200°C and 200 h with 20 thermal cycles at 1400°C, indicating excellent oxidation resistance and thermal shock resistance of the coating. The good thermal shock resistance is attributed to the compositional gradient in the coating.