Initiation and Propagation Behaviors of Fatigue Cracks in X60 Pipeline Steel in Hydrogen Environment

Fatigue life and fatigue crack growth tests were performed on X60 pipeline steel in a gaseous environment containing 10% (volume fraction) H₂ at a total pressure of 12 MPa. The fatigue crack initiation and propagation behaviors of X60 pipeline steel in a hydrogen environment were investigated, and the effects of hydrogen pre-charging and loading frequency were examined. The results show that hydrogen reduced the fatigue crack propagation life of X60 pipeline steel under a loading frequency of 1 Hz, but its effect on crack initiation life was not significant. Meanwhile, pre-charging with hydrogen for 10 h decreased both the crack initiation life and the crack propagation life under the same loading frequency. In the 10% hydrogen environment, the fatigue life of X60 pipeline steel was close under loading frequencies of 1 Hz and 2 Hz. However, when the loading frequency was reduced to 0.5 Hz, the crack initiation life decreased obviously, leading to a corresponding reduction in fatigue life. In the 10% hydrogen environment, the fatigue crack propagation rate was 9.56 times higher than that in the hydrogen free environment, and hydrogen reduced the threshold stress intensity factor range (ΔK_th) required for crack propagation.