Effect of tensile dwell on high-temperature low-cycle fatigue and fracture behaviour of cast superalloy MAR-M247

Hot isostatically-pressed, nickel-based superalloy MAR-M247 was tested under fatigue and creep-fatigue conditions. Continuous cycling and cycling with 10 min tensile dwells in each cycle were applied in symmetrical strain control cycle with constant total strain amplitude at 900 °C in air. Cyclic hardening/softening curves, cyclic stress-strain curves and fatigue life curves were obtained. The introduction of tensile dwells resulted in lower fatigue life in total strain representation. Surface relief, specimen sections and fracture surface observations revealed crack initiation sites, crack density and crack paths, and help to clarify the effect of dwells on fatigue behaviour.