Comparison of in-beam fatigue behavior between austenitic and ferritic steels at 60° C

Fatigue response was investigated for both 20% cold-worked 316 (316CW) austenitic stainless steel and F82H ferritic steel under 17 MeV proton irradiation at 60° C. The loading mode was stress-controlled and tension–tension with two different loading ratios, R=0.44 and 0.2 for both steels. The number of cycles to fracture (Nf) increased substantially under irradiation for both steels at R=0.44, while the increase of Nf in the in-beam specimens disappeared for both steels at R=0.2. Although the actual fatigue lifetime was generally similar in the unirradiated specimens of 316CW steels at R=0.44 and F82H steel at R=0.2, the prolongation of the lifetime under irradiation was detected only for 316CW steel at the respective loading mode. In this study, the dynamic irradiation effect on fatigue response will be discussed with respect to its dependence on the loading ratio (R) and the crystal structure (fcc/bcc).