Fatigue Behavior of Non-Oxide Ceramics at Elevated Temperature

Abstract

Cyclic and static fatigue tests were carried out using tensile specimen to clarify the fatigue behavior of silicon nitride and silicon carbide. The cyclic fatigue strength of silicon nitride on 107 alternating cycles is about 60% of the original mean tensile strength at room temperature. With increasing temperature, the cyclic fatigue strength decreases due to slow crack growth and creep deformation. The static fatigue strength of silicon nitride also degraded with increasing temperature. In slow crack growth failure without creep deformation, the power law for crack growth rate controlled the strength degradation. In creep deformation regime, the modified Larson-Miller parameter was applicable to life prediction under static stress. On the other hand, the cyclic fatigue phenomenon in silicon carbide is observed at elevated temperature, but not at room temperature. The difference of fatigue behavior between silicon nitride and silicon carbide was caused by microstructure characteristics.