Study on low-cycle fatigue property of 316 stainless steel at room temperature and 350 ℃

Low cycle fatigue property of 316 stainless steel was investigated at room temperature (RT, both base material and weld bead) and 350 ℃ (base material) under a strain amplitude (SA) range from ± 0.3% to ± 1.5%, and fracture morphology of representative samples was observed by scanning electron microscope(SEM). The results showed that, 316 stainless steel had an excellent fatigue property. Compared with 350 ℃, the fatigue life was 30%-50% longer at RT in the same SA, while the fatigue life of the base material was twice than that of the weld bead in the same SA. The decreasing of the fatigue life and the rising of the peak stress coincides with the increasing of the SA. The peak stress has a corresponding drop with the rising of cycles at RT, both base material and weld bead; however, the cyclic hardening turned into cyclic saturation, resulting from the increasing of the SA at 350 ℃. The fatigue crack source and striation was found at the surface of the samples by SEM, the striation gap became longer in accordance with the rising of SA, and in the same SA, the striation gap of weld bead was longer than that of base material, while that of 350 ℃ was longer than RT, which matched the fatigue experimental results. (authors)