OS0804 窒化ケイ素/炭化ケイ素複合材の低酸素分圧下におけるき裂治癒可能な限界応力(ガスタービン材料の各種力学特性,オーガナイズドセッション)

抄録

The crack-healing behavior of Si_3N_4/SiC composite under constant stress and low-oxygen pressure was investigated. A semi-elliptical surface crack with length of about 100 μm was introduced on the center of tensile surface by the indentation method. These specimen were healed at 1200℃ for 5h under tensile stress (σ_<app> = 0 - 300 MPa) in low oxygen partial pressure (Po_2= 50-21000 Pa). The threshold constant stresses for crack-healing were defined 200 MPa in oxygen partial pressure over 500 Pa. The bending strength of crack-healed specimens under tensile stress in Po_2≧500 Pa showed the almost the same value to that of specimens healed , and most specimens fractured from out-side crack-healed zone. From these results, the crack healing can be achieved during service condition and can be elongate the lifetime and the reliability in Si_3N_4/SiC composite ceramic.