638 Si_3N_4/SiC 複合セラミックスき裂治癒材の高温低サイクル疲労強度特性と負荷中のき裂治癒挙動

概要

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Silicon nitride containing both 8wt% yttrium oxide as a sintering additive and 20wt% silicon carbide particles (average grain size 0.03μm) was hot-press sintered. Using the material, low fatigue strength of crack-healed and proof-tested specimens (CP specimens) at elevated temperature and crack-healing behavior under both static and cyclic loading at 1200℃ in air were investigated in this study. A semi-circular pre-crack with about 110μm in diameter was introduced on the center of the tensile surface of specimens using a Vickers hardness indenter. Crack healing was performed at 1300℃ for 1 hour in air. The fatigue strength of the CP specimen decreased slightly with increasing test temperature. However, the crack-healed part is no sensitive to low cyclic fatigue below temperatures of 1400℃. The process of "crack-healing+proof test at R.T" is useful for improving the reliability for fatigue strength of Si_3N_4/SiC composite below temperatures of 1000℃. In the present material, a 110μm surface crack could be healed perfectly under both static and cyclic loading with a frequency of 0.001 to 5Hz at 1200℃ in air. Bending strength of the specimens crack-healed under loading was restored to as-received level.
社団法人日本機械学会の論文
2000-10-05