The effect of dwell on thermomechanical fatigue in superaustenitic steel Sanicro 25

Superaustenitic steel Sanicro 25 has been subjected to out-of-phase thermomechanical fatigue cycles with 10-min dwell at peak temperature in the temperature range from 250 degrees C to 700 degrees C. The effect of the dwells on the cyclic response, internal structure and damage mechanism was studied. Cyclic hardening/softening curves, cyclic stress-strain curves and fatigue life curves were evaluated. The internal structure and nanoparticles representing the obstacles for dislocation motion were analysed and identified by energy dispersive X-ray spectroscopy in scanning transmission electron microscope. Scanning electron microscopy combined with focused ion beam and electron backscatter diffraction was adopted to reveal the respective mechanisms responsible for fatigue crack nucleation and propagation. Effect of dwells in in-phase and in out-of-phase cycling on the fatigue behaviour, on the modification of internal structure and damage mechanisms, were analysed and discussed.

Automated summary

The superaustenitic steel Sanicro 25 was subjected to out-of-phase thermomechanical fatigue cycles with dwell at peak temperature within the range of 250°C to 700°C. The effects of dwell on cyclic response, internal structure, and damage mechanism were studied, evaluating cyclic hardening/softening curves, stress-strain curves, and fatigue life curves. Various advanced microscopy techniques were used to analyze internal structure, nanoparticle obstacles for dislocation motion, and mechanisms responsible for fatigue crack nucleation and propagation. Discussions were made on the effects of dwells in in-phase and out-of-phase cycling on fatigue behavior, internal structure modification, and damage mechanisms.