Oxidation and defect control of CVD SiC coating on three-dimensional C/SiC composites

Two kinds of multi-layer CVD SiC coatings were prepared on a three-dimensional C/SiC composite. Oxidation behavior of the coating and the composite were Studied and the effect of defects in the coating on its oxidation protection property were investigated. Above 1200 degreesC, thickness of the oxide film formed on the coating was related to oxidation time by the Fick's first law X(t)(2)=Bt, the diffusion rate constant increased with oxidation temperature according to the Arrhenius' relation ln B= -32 483/T + 1.4048. Morphology of the interface between the CVD SiC and its oxide film was different after oxidation at temperatures from 1200 to 1500 degreesC. It as interpreted by consideration of the interfacial stress produced by thermal expansion mismatch and the CO gas pressure produced by interfacial reaction. (C) 2002 Elsevier Science Ltd. All rights reserved.