Cross-methodological assessment of hydrogen embrittlement thresholds in high-strength Cr-Mo and pipeline steels using various techniques

This study provides a cross-methodological validation of HE thresholds for three representative body-centered cubic steels: SA-372 Grade J, API X70, and API X42 pipeline steels. Smooth tensile, notched tensile, small punch, and disk burst tests were conducted in ambient air and in 10 MPa gaseous hydrogen at room temperature. The results show that all three steels exhibit severe ductility loss in hydrogen with relative reduction of area (RRA) values of 0.51, 0.49, and 0.54, respectively, while tensile strength remains unaffected. Notched tensile testing reveals relative notched tensile strength values of 0.76 (SA-372), 0.86 (X70), and 0.91 (X42), indicating that lower-strength grades retain higher notched strength. The small punch test, with its biaxial stress state, shows the highest HE sensitivity. Disk burst testing demonstrates a strong ramp-rate dependence of the Z-factor with values ranging from 1.2 to 1.9, all below the ISO 11114–4 limit of 2.0. Despite large differences in absolute values, the ranking of susceptibility (SA-372 > X70 > X42) is consistent across all methods. The cross-methodological consistency confirms that relative HE susceptibility is an intrinsic material property, enabling the use of the most convenient test method for initial screening when appropriately calibrated thresholds are applied.