Cyclic deformation behavior and fatigue life prediction of 316H stainless steel under strain-controlled fatigue

In this study, low-cycle fatigue tests were conducted on 316H stainless steel at room temperature and at the service temperature of 600 °C. The material exhibits highly strain-amplitude-dependent fatigue lives and distinct cyclic deformation modes at both temperatures. At room temperature, the cyclic response transitions from conventional hardening-softening at high strain amplitudes to a distinct secondary hardening regime at low strain amplitudes. At 600 °C, 316H stainless steel exhibits pronounced cyclic hardening at high strain amplitudes and rapid cyclic stabilization at lower amplitudes. EBSD results showed that martensitic transformation occurred mainly at high strain amplitudes, indicating that the secondary hardening at room temperature is primarily dislocation-related. By capturing the transition trend of the cyclic deformation behavior, a modified flow stress-based life prediction model is proposed. The modified model accurately captures the fatigue life across both temperature regimes, with all predictions falling well within a factor of 1.5× error band.