Abstract
Silicon-carbide-coating is generally formed for the improvement of oxidation resistance of carbon/carbon matrix composites (C/Cs). Underneath a SiC coating thin conversion layer is often inserted to improve bonding strength between coating and C/C composite. The conversion treatment represents chemical reaction between the substrate carbon and gaseous Si. Two source materials, SiCl4 and SiO were examined to yield the conversion layer, and the mechanisms for the growth of a conversion layer were discussed, where the formation rate of a conversion layer was placed a special attention. Then, improvement of the interfacial shear strength of SiC-coated C/C composites by the conversion treatment was determined by a plunger method as a function of conversion time and treatment temperature, and the surfaces and cross-sections near the interface were observed by SEM and EPMA. These results indicate that the strengthening of the interfacial bonding by longer treatment time and higher treatment temperature is caused by so-called anchor effect due to the infiltration of CVD SiC in defects in a substrate C/C.
