Effects of implanted hydrogen on fatigue behavior of F82H under irradiation

In situ stress-controlled fatigue tests were performed for F82H steels under 17 MeV proton irradiation with an energy degrader at 60 °C. The energy degrader enhanced the hydrogen implantation rate from 2.6 × 10−6 to 1.3 × 10−3 appm/s at a dose rate of 1.1 × 10−7 dpa/s. Although number of fatigue cycles to fracture (NF) under irradiation without the degrader increased to about 2 times NF for the unirradiated condition, only a slight increase of NF (1.2 times) was detected for the irradiation with the degrader. The surface morphology of the fracture surfaces was similar for both in situ irradiation fatigue specimens with and without the degrader. A modified technique of fractographic surface topography analysis (FRASTA) demonstrated rapid crack propagation under irradiation with the degrader. Substantial levels of implanted hydrogen play a role in reducing the effect of irradiation on fatigue behavior based on the interaction between radiation-induced defect clusters and moving dislocations.