Effects of artificial defect on the material residual strength of SiC ceramics after thermal-shock

Thermal shock behaviors of SiC ceramic with artificial defects were studied. Artificial surface cracks were simulated by Vickers and Knoop indentations, and artificial inner cracks were obtained using novel method of introducing plastic fibers. The residual flexural strength and microstructure were analyzed. The flexural strength of artificial defect free SiC ceramic maintains minimum 87% of the original strength after thermal shock ΔT no more than 400 ℃, and the residual strength of those with artificial crack, no matter surface type or inner type, can still be improved by the joint effect of thermal treatment, thermal shock and the stress relaxation by artificial crack if ΔT no more than 400 ℃. It is believed that inner and surface artificial defects ease the crack propagation during the thermal shock process.