Fatigue characteristics and fatigue limit prediction of an induction case hardened Cr–Mo steel alloy

In this study, a structural Cr–Mo steel alloy is used to investigate the effect of residual stresses and the presence of micro-holes on the fatigue strength for the base metal and the induction case hardened specimens. The samples are tested using rotary bending. Micro-hole diameter and case hardening depth are used as varying parameters. For the prediction of the fatigue limit, the results from fatigue experiment, and fracture mechanics parameters related with local hardness and defect size are used. A previously proposed equation to predict the fatigue strength is modified and the results show good agreement with experimental data. In the proposed equation, a new parameter is introduced to consider the effect of stationary crack with defect. In addition, an empirical method of modifying residual stress effect on the fatigue strength is proposed to examine the mean stress effect of fatigue loading.