Borosilicate Glass‐Induced Fiber Degradation of SiC/BN/SiC Composites Exposed in Combustion Environments

Abstract

Three SiC/ BN /SiC composite specimens reinforced with different SiC fibers (Sylramic, Sylramic‐ iBN , and Hi‐Nicalon Type S) were exposed in a combustion environment. Exposures were carried out for 151 h in a fuel‐lean high pressure burner rig at 0.9 MPa total pressure, sample temperatures near 1573 K, and a gas velocity of 15 m/s. Weight loss of all three composites was observed. Extensive oxidation of SiC fibers was observed in cracked locations. A mechanism based on borosilicate enhanced oxidation coupled with volatilization of boria is described. Ramifications of this degradation mechanism are discussed for long‐term applications of SiC/ BN /SiC composites in combustion environments.