Bending fatigue strength of austenitic stainless steel SUS316 in mercury

Naoe, Takashi   ; Yamaguchi, Yoshihito ; Futakawa, Masatoshi  ; Wakui, Takashi  

Liquid mercury target system for spallation neutron source is installed at Materials and Life Science Experimental Facility in J-PARC. Austenitic stainless steel SUS316 for a structural material of the target vessel is contact with mercury, and imposed by cyclic pressure that is induced by pulsed proton beam injection at 25 Hz. Therefore, it is important from the viewpoint of the structural integrity to investigate the effect of mercury on fatigue behavior of the structural material. Bending fatigue tests in mercury and air were performed to evaluate the effect of mercury on fatigue behavior. FRActure Surface Topography Analyses (FRASTA) were carried out to evaluate the change in fracture morphology with mercury. It was confirmed that the fatigue strength was decreased by mercury immersion in low cycle region less than 10 cycles and intergranular fracture surface was observed, while in high cycle region the mercury immersion effect was hardly recognized.