SIMPLE METHOD OF SIC COATING ON CARBON CA RBON COMPOSITES AND EVALUATIONS OF OXIDATION RESISTANCE/

SiC coatings for oxidation protection of Carbon-Carbon (CIC) composite s were produced by the Si/Polymer (S/P) process and the SiC/C/Polymer (S/C/P) process; these processes are much simpler than the conventiona l CVD process. Oxidation tests were also carried out to evaluate effec tiveness of the coatings. In the S/P process, C/C composites were coat ed with slurry of Si particle-polymer mixtures. The slurry coated comp osites were then heat treated to carbonize the polymer and form SIC by the liquid silicon-carbon reaction. Porous and dense two-layer SiC co atings were observed. As for the S/C/P process, a carbon layer contain ing SIC particle was first formed on C/C composite; this layer was the n reacted with impregnated liquid silicon. A dense SiC layer was there fore formed through the S/C/P process. Although the oxidation rates of C/C composites were reduced in all the testing temperatures (900 simi lar to 2000 K), the SiC coatings by the S/P process mere less effectiv e than those by the CVD process. This was explained by small and nonun iform thicknesses of the dense SiC layer in the coatings by the S/P pr ocess. On the other hand, C/C composites coated by the S/C/P process s howed almost the same oxidation rates as those by the CVD process.