抄録
Si3N4/SiC composite ceramics with large crack-healing ability were sintered and subjected to three-point bending. Semi-elliptical surface crack of 100μm surface length was made on each sample. By this crack, strength was reduced to about 50%. The crack-healing behavior under cyclic stress of 5Hz, and resultant cyclic fatigue strengths at the healing temperature of 900°C∼1200°C were systematically investigated. The main conclusions : (1)This Si3N4/SiC sample could heal a crack at 900°C∼1200°C even under cyclic stress of 5 Hz frequency. (2)The bending strength of cracked sample was about 400MPa. In the case where applied stress was larger than 350MPa, the sample was fractured during crack-healing process. On the other hand, in the case where applied stress was smaller than 300MPa, the crack was completely healed. (3)The crack-healed sample exhibited high cyclic fatigue strength at each crack-healing temperature. (5)Finally, it was concluded that this sample exhibited self-crack-healing ability during service.
