Abstract
Fatigue test of Inconel 718 was conducted at high temperature (923K) using compact tension specimens. Microstructures of the longitudinal cross section of the fractured specimens were observed together with the fracture surfaces. Fatigue test at room temperature and creep test at high temperature were also conducted for the comparison. It has been verified that the intergranular fracture mode was predominant at high temperature whether the fracture was due to creep or creep-fatigue. However, at room temperature, the fatigue fracture mode was transgranular. Furthermore, microcracks which is almost perpendicular to the main crack were observed in the specimens fractured by creep or creep-fatigue. Oxidation at the grain boundaries at creep-fatigue condition was not verified by the EPMA analysis.
