高温低サイクル疲労における微小き裂の発生と伝ぱへの粒界反応型析出の影響

概要

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Effects of serrated grain boundaries on the initiation and growth of short fatigue cracks were investigated using austenitic 21-4N heat-resisting steel at 973K in air. Grain boundaries were serrated by the grain-boundary reaction (GBR) precipitates. Fatigue cracks were initiated at second-phase particles and on the grain boundaries on which GBR precipitates did not form. Therefore, the crack initiation life in the specimens with serrated grain boundaries was almost identical to that in the specimens with straight grain boundaries. However, the subsequent short crack growth was influenced considerably by serrated grain boundaries, and the crack growth rate decreased more in the specimens with serrated grain boundaries than in the specimens with straight grain boundaries. The fatigue cracks were largely deflected at the GBP nodules on the grain boundaries. The deflection of the fatigue cracks was one of the most important factors for improvement of the fatigue crack growth resistance when crack length was less than a few hundred m.
社団法人日本機械学会の論文
1989-07-25