Subcritical crack growth in silicon carbide

Crack growth behaviour in two types of commercially available silicon carbide was examined from 600 to 8500C in ambient atmospheres containing oxygen, water vapour, and sulphur dioxide. The double-torsion specimen was used in the incremental displacement rate mode to yield (K1, V) relations. The direct-bonded material exhibited unstable crack propagation and arrest behaviour which was not measurably affected by temperature variations or the corrosive environments. The hot-pressed material exhibited subcritical crack growth similar to the three regions of the classical (K1, V) diagram. Oxidation of the silicon carbide is suggested to be the mechanism of stress corrosion operating in these environments. (author)