Modelling the Effects of Hydrogen Pressure on Fatigue Crack Growth Behavior in SA372 Pressure Vessel Steels

Low alloy ferritic steels used in fabricating cost-effective cylinders for hydrogen storage are susceptible to hydrogen embrittlement. A model first proposed by Amaro et al. (ARFiDS model) for predicting the effects of hydrogen pressure on the kinetics of hydrogen assisted fatigue crack growth (HA-FCG) in X-100 pipeline steels for pressure between 1 and 20 MPa is adapted in this study and used for predicting the HA-FCG behavior of SA372 Grade J Class 70 pressure vessel steels for pressures ranging between 10 and 102 MPa. The crack growth kinetics in these steels exhibit a typical two-region behavior labelled as the transient and steady-state regions, characterized by distinct power-law exponents in the relationship between fatigue crack growth rate, da/dN, and the cyclic stress intensity parameter, ΔK. The predicted HA-FCG behavior from the model is compared with experimental data for SA 372 steel for hydrogen pressures ranging from 10 to 102 MPa and is shown to perform well for load ratios, R, of 0.2 and 0.5 over a wide range of crack growth rates. The phenomenological basis for the model is discussed.