High Temperature Strength Characterization of Sintered Alpha Silicon Carbide.

Uniaxial tensile and flexural stress rupture testing of sintered alpha-SiC Carborundum 1980 material was carried out at 1200 to 1400 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 slow crack growth associated with surface connected porosity failure sites. The extent of slow crack growth increased with increasing temperature and large regions of SCG were observed in tests made at 1300 C. These observations were supported by flexural stress rupture testing at 1300 and 1400 C. Slow crack growth is characterized primarily by intergranular crack propagation while fast fracture brittle failure occurs transgranularly. The uniaxial tensile stress rupture testing is much more sensitive in revealing the time-dependent crack growth behavior, especially at lower temperatures such as 1200 C in air, than flexural stress rupture testing.