EFFECTS OF HYDROGEN ON BEHAVIOR OF LOW-CYCLE FATIGUE OF 2.25CR-1MO STEEL

The effects of hydrogen atoms on behaviour of low cycle fatigue of 2.2 5Cr-1Mo steel have been investigated in present work. The results indi cate that the cyclic softening rate and low cycle fatigue life are res pectively increased and reduced remarkably by hydrogen atoms. In addit ion, hydrogen atoms make the original stress amplitude of low cycle fa tigue increase, which is because of the drag effect of hydrogen atoms on the moving dislocations. Analyses using electron microscopy show th at hydrogen atoms accelerate crack initiation of low cycle fatigue fro m inclusion and transfer the source of low cycle fatigue crack from th e surface of specimen to the inclusion, which results in the marked de crease of low cycle fatigue life. The increase of cyclic softening rat e for hydrogen charged specimen is due to hydrogen atoms accelerating the initiating and growing of microvoids from the secondary phase part icles in the steel. The reducing of the drag effect of hydrogen atoms on moving dislocations is also helpful to the increase of the cyclic s oftening rate.