Preparation of a multi-composition coating for oxidation protection of modified carbon-bonded carbon fiber composites by a rapid sintering method

In order to improve the oxidation resistance of carbon-bonded carbon fiber composites, a multi-composition coating consisting of multilayer ZrB₂-SiC whiskers(SiCw)-borosilicate/ZrB₂-MoSi₂-SiCw-borosilicate was prepared on the surface of ZrB₂-modified carbon-bonded carbon fiber composites (M-CBCF) by a rapid sintering method in trace amounts of oxygen environment. The inner-layer ZrB₂-SiCw-borosilicate was first prepared by instantaneous vacuum-impregnation to seal the surface pores of M-CBCF, and the outer-layer ZrB₂-MoSi₂-SiCw-borosilicate was obtained by slurry spraying. The multilayer-coated composites were embedded in graphite powders and sintered at 1723 K for 10min in atmosphere. The results showed that the prepared ZrB₂-SiCw-borosilicate/ZrB₂-MoSi₂-SiCw-borosilicate coating had remarkable oxidation resistance and could protect M-CBCF from high-temperature erosion. The weight loss rate of the double-layer-coated composites was only 0.44% after oxidation for 100min at 1773K, while the weight loss rate of inner-layer-coated composites reached 25.35%. The oxidation resistance of multilayer coating was mainly attributed to the high viscosity of glass phase, matched thermal expansion coefficient and the toughening effect of SiC_w.