Crack Propagation Rates of SUS 321 Stainless Steel under High-Temperature, Low-Cycle Fatigue Conditions

Abstract

Crack propagation rates of SUS 321 stainless steel under high-temperature, low-cycle fatigue conditions were obtained from the observation of fracture surfaces. There were good linear relations between the crack propagation rate and the crack length in log-log plots, whether the fracture mode was transgranular or intergranular. The slopes in the log-log plots were varied from 1.2 to 1.5, but many of them were 1.3. The proportion of the cycles spent in Stage II to the fatigue life could be expressed as a function of the fatigue life. Its calculated proportion was coincident with the proportion of the number of striations on the fracture surface to the fatigue life. The crack propagation rate at 700°C could be expressed in terms of the plastic strain range, the strain rate and the crack length. This result was discussed in comparision with other studies.