Crack‐Healing Behavior Under Stress of Mullite/Silicon Carbide Ceramics and the Resultant Fatigue Strength

Mullite/SiC composite ceramics were sintered and subjected to three‐point bending of specimens made according to the appropriate JIS standard. A semicircular surface crack 100 to 250 μm in diameter was made on each specimen. We systematically studied crack‐healing behavior and cyclic‐ and static‐fatigue strengths at room temperature and 1000°C (crack‐healing temperature) by using three types of specimens (smooth, cracked, and crack‐healed). The main conclusions are as follows: (i) mullite/SiC composite ceramics have the ability to heal after cracking; (ii) crack‐healed specimens exhibited higher static and fatigue strengths than those of smooth specimens, which was caused by crack‐healing; (iii) a sample crack‐healed at 1000°C had a high fatigue strength at 1000°C; and (iv) mullite/SiC ceramics can heal a crack under stress at 1000°C, and this behavior was considered using crack‐driving force and crack‐healing force, qualitatively.