CRACK-HEALING BEHAVIOUR OF Si{sub}3N{sub}4 CERAMICS DURING SERVICE AND RESULTANT FATIGUE STRENGTH IN THE HEALED CONDITION (1000°C - 1200°C, IN AIR)

摘要

Si{sub}3N{sub}4/SiC composite ceramics were sintered and subjected to three-point bending. A semi-elliptical surface crack of 100 μm in surface length was made on each specimen. Crack-healing behaviour under cyclic stress and resultant cyclic fatigue strength were systematically investigated at healing temperatures of 1000°C and 1100°C. Si{sub}3N{sub}4/SiC composite ceramics have the excellent crack-healing ability even under cyclic stress at a frequency of 5 Hz. Moreover, the crack-healed sample exhibited high cyclic fatigue limits at healing temperatures of 1000°C and 1100°C.