Observation In-situ for Propagation of Low Cycle Fatigue Crack at Inclusions and Grain Boundary of 2.25CrMoV Steel

High stress low cycle fatigue test was carried out on 2.25CrMoV steel used for rotor at vacuum and room temperature. Propagation of crack originate from typical defects such as inclusions and grain boundaries were continuous observed in-situ, the effects of typical defects on initiation and propagation of fatigue crack were studied. The results show that the shape and size of inclusions had no obvious influence on fatigue crack propagation under the high stress cyclic loading. The propagation rate of the crack initiated by inclusion was less than that of the crack initiated at grain boundary. The interaction between short crack group and the rapid increment of slip line was the main reasons of this sample destruction.