Fatigue Crack Initiation of F82H Reduced Activation Ferritic/Martensitic Steel

To improve the fatigue life assessment of the relatively thin wall structure of the fusion reactor blanket, the fatigue micro-crack initiation behavior of the F82H steel at room temperature was investigated. The micro-crack initiation life was approximately 20–30 % of the fatigue life. The crack initiation was observed at the prior austenitic grain boundary, the packet boundary, the block boundary, and the inside of the block structure. The majority was the transgranular crack initiation, which exceeded 90 % of the all. The effect of the irradiation damage (irradiation hardening) was only a shortening of the micro-crack initiation life. No change of the micro-crack initiation sites and their ratio were observed.