750 窒化ケイ素セラミックスの繰返し応力下におけるき裂治癒挙動  [in Japanese] Crack-healing behaviors of Si_3N_4/SiC under cyclic stress  [in Japanese]

Si_3N_4/SiC composite ceramics were sintered and subjected to three-point bending. A semi-elliptical surface crack of 100μm in surface length was made on each specimen. The pre-cracked specimens were subjected to crack-healing under a cyclic bending stress of 5 Hz and the resultant bending strength and fatigue strength were investigated. The threshold stress for crack-healing, below which the pre-cracked specimens recovered their bending strength, was 300MPa at 1000℃ and 1200℃, which was 75% of the bending strength of the pre-cracked specimens. The crack-healed specimens exhibited quite high cyclic fatigue strength at crack-healing temperatures of 1000℃ and 1200℃.