In-beam fatigue behavior of F82H steel at 500 °C

Abstract

Stress-controlled fatigue tests were conducted for side-notched small specimens of F82H steel under in-beam and unirradiated conditions with 17 MeV protons at 500 °C. The environment for the fatigue tests was impure He gas containing 10–3000 ppm oxygen. The number of cycles to fracture ( N f) was slightly reduced under irradiation. SEM examination of fracture surfaces indicated the formation of an oxide film in the vicinity of notch tip only for the in-beam specimens. Optical microscopic observation demonstrated oxidation not only along the grain boundaries but also on the crystallographic slip planes on the specimen surfaces of both in-beam and unirradiated specimens. The oxidation appeared to be enhanced to form numerous oxidation pits on the surface, especially for the in-beam specimens. In this study, the in-beam fatigue behavior at 500 °C is discussed with respect to the dynamic irradiation effect in the low oxygen potential atmosphere.