Abstract
The low-cycle fatigue tests with varying stress hold time at the tensile maximum stress were conducted on the circumferentially grooved specimens of 18 Cr-8 Ni-Mo stainless steel (SUS 316) at 550°C. The results of micro-fractographical study are as follows:
(1) In general, the shorter hold time condition gave the transgranular fracture mode, and the longer hold condition gave the intergranular mode. Intergranular facets appeared when the average propagation rate (ΔS/tH) became less than 10-3mm/min.
(2) The striation spacing was not affected by the duration of stress hold. Therefore, the stress hold time seems to affect the crack propagation rate only during the initial fatigue stage where the striation pattern is unobservable.
