2022 年 108 巻 3 号 p. 191-198
Fatigue crack propagation (FCP) behavior was studied on three kinds of zero thermal expansion (ZTE) alloy. The specimens manufactured by three different processes, i.e., casting, forging and laser additive manufacturing: selective laser melting (SLM), were employed. The FCP rates in casted alloy were almost same with SS400 which was used for comparison. In SLM product, FCP rates were higher than casted alloy and slightly higher than forged alloy especially in low ∆K region. The characterization of fracture surfaces was conducted by scanning electron microscope. Through the observation, rough crack surface was observed in casted alloy, on the other hand, small marks along the crack propagate direction were observed in SLM specimen. In order to consider the effective stress intensity factor range, the crack opening load was measured to estimate FCP behavior. In evaluation by the effective stress intensity factor range, FCP rates of the specimens with three kinds of manufacturing processes were similar. From these results, it is concluded that the ZTE alloy, manufactured by SLM showed enough performance in FCP examination compared with forged alloy. The difference in the results between the two products is attributed to the difference in the fracture surface due to the different microstructure.
