Effects of hydrogen pressure on hydrogen-assisted fatigue crack growth of Cr-Mo steel

The fatigue crack growth rates (FCGRs) of 4130X steel in 45, 70, 87.5 and 100 MPa hydrogen were measured, and the hydrogen concentrations at the crack tip of test specimens were analyzed by establishing a hydrogen transport model. This model can describe the hydrogen behaviors in the process of environmental embrittlement. Results show that the FCGR increases with the increase in hydrogen pressure. However, the acceleration reaches the threshold under 87.5 MPa. Hydrogen pressure has the same influence on hydrogen concentration, and the threshold of the effect is probably related to the fact that the hydrogen absorption on the material surface reaches the limit.