Crack-healing behavior of Si3N4/SiC ceramics under stress and fatigue strength at the temperature of healing (1000 °C)

Si3N4/SiC composite ceramics were sintered and subjected to three-point bending specimens made according to the appropriate JIS standard. A semi-circular surface crack of 100 μm in diameter was made on each specimen. We systematically studied crack-healing behavior, and cyclic and static fatigue strengths at the service temperature (1000 °C) by using three kinds of specimens (smooth, cracked and crack-healed). The main conclusions are as follows: (1) Si3N4/SiC composite ceramics have the excellent ability to heal a crack at 1000 °C; (2) this sample could heal a crack even under cyclic stress at 1000 °C; (3) a new crack-healing process was proposed. The sample crack-healed at 1000 °C by the process exhibited a sufficient static and cyclic fatigue strength at 1000 °C.