Oxidation resistant SiC coating for graphite materials

A dense functional gradient SiSiC coating with good oxidation resistance wh en 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 p rimary coating, and pinholes were filled with free silicon. The mechanism f or the formation of a continuous SIC coating on graphite was investigated e xperimentally and theoretically. Oxidation tests were conducted from 800 de grees C to 1600 degrees C for up to 1000 h. Samples of graphite with the Si SiC coating were found to be totally intact after oxidizing for 1000 h toge ther with 100 thermal cycles at 1200 degrees C and 200 h with 20 thermal cy cles at 1400 degrees C, indicating excellent oxidation resistance and therm al shock resistance of the coating. The good thermal shock resistance is at tributed to the compositional gradient in the coating. (C) 1999 Elsevier Sc ience Ltd. All rights reserved.