Study on Low-Cycle Fatigue Property of Candidate Stainless Steels for SCWR

Low cyclic fatigue property of three austenitic stainless steels （316Ti, 347 and HR3C） as candidate materials for SCWR was investigated at room temperature（RT） and 650℃ under a strain amplitude of ±0.5%, and fracture morphology of all the samples was observed by scanning electron microscope（SEM）. The results showed that, at both temperatures the fatigue life of 347 was best and 316Ti worst. For each material, the area of hysteresis was nearly the same in the two temperatures. The elastic deformation was 0.1%-0.15% both at RT and 650℃ for the three materials with different fatigue lives, indicating it had no direct connection with fatigue life. There was different cyclic hardening/saturation behavior for each material. The maximum/minimum stress of either HR3C or 347 was quite different at the two temperatures, while of 316Ti was almost the same. The cyclic hardening behavior was more remarkable in 316Ti compared with 347 at 650℃. SEM observation found that the fatigue striation width was only 1.87 μm for 347, but up to 4.67 μm and 3.0 μm for 316Ti and HR3C respectively, which further demonstrated that 347 had the best fatigue property at 650℃.