High temperature uniaxial tensile stress rupture strength of sintered alpha SiC

Uniaxial tensile stress rupture testing of sintered-SiC was carried out at 1200 and 1300° C in air at various applied stress levels and the corresponding times-to-failure were measureD. Fractographic evidence from uniaxial tensile stress rupture testing at 1200° C revealed limited presence of subcritical (slow) crack growth associated with surface connected porosity failure sites. The extent of slow crack growth (SCG) increased with increasing temperature and large regions of SCG were observed in tests made at 1300° C. An estimate of the crack velocity exponent,n, in the crack velocity—stress intensity factor relation,V=AK ₁ ⁿ , for SCG has been made. Slow crack growth is characterized primarily by intergranular crack propagation while fast fracture (catastrophic failure) occurs transgranularly.