Ni基超合金の疲労強度に及ぼす繰返し速度の影響

概要

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In order to investigate the growth mechanism of a fatigue crack of Ni-based super alloy at ultrasonic frequency, ultrasonic fatigue and rotating bending fatigue tests were carried out for Inconel 718 in ambient air and in N_2 gas using plain and notched specimens and the results in both tests were compared by focusing on the effects of strain rate and environment. In ambient air, fatigue strength was higher in ultrasonic fatigue than in rotating bending fatigue in plain specimen, while the results in notched specimen were the reverse. Many transgranular cracks and cleavage like cracks were observed on the fracture surface in ultrasonic fatigue in addition to striation and transgranular facets observed in rotating bending fatigue and there was no difference in the fracture mechanism between plain specimen and notched one. Moreover, these effects of frequency on the growth mechanism of a crack in ambient air were nearly the same in N_2 gas, though fatigue strength in N_2 gas was higher than that in air. The increase in fatigue strength in N_2 gas was mainly caused by the retardation of a crack initiation.
社団法人日本機械学会の論文
2006-10-25