Low-cycle fatigue characteristics of Cr18Mn18N0.6 austenitic steel under strain controlled condition at 100 °C.

Highlights • The low-cycle fatigue behavior of Cr18Mn18N0.6 austenitic steel is studied under strain controlled condition. • Cyclic softening that is affected by the ratio of tensile strength over yield stress is found. • Relationships such as stress-life and strain-life are analyzed with theoretical equations. • Dislocation structures with twins during fatigue test are observed via transmission electron microscopy. • Cr18Mn18N0.6 austenitic steel possesses a higher low-cycle fatigue resistance compared with conventional steel alloys. Abstract Low-cycle fatigue characteristics (e.g. cyclic stress-strain curves, strain-life curves, stress-life curves, and transition fatigue life) of austenitic stainless steel Cr18Mn18N0.6 used for supercritical turbogenerator retaining rings were studied under an axial strain controlled condition with total strain amplitudes ranging from 0.005 to 0.0085 at working temperature 100 °C. Cr18Mn18N0.6 was found to be cyclic softening during low-cycle fatigue with the extent and rate of cyclic softening increasing with strain amplitude. Stress amplitude decreased more rapidly for larger applied total strain amplitude. The transition fatigue life of Cr18Mn18N0.6 was found to be about 2177 cycles. Fatigue crack initiated from a relatively flat zone at the specimen surface due to persistent slip band and surface roughening. Cr18Mn18N0.6 austenitic stainless steel was found to possess a high low-cycle fatigue resistance compared with conventional steel alloys like 304 stainless steel. [ABSTRACT FROM AUTHOR]