Establishing thresholds for hydrogen embrittlement in SA-372 Grade J steel: Insights from conventional tensile, disk burst, and small punch testing

This study evaluates the hydrogen embrittlement susceptibility of SA-372 Grade J steel by employing multiple experimental methods, including smooth tensile testing, notched tensile testing, disk burst testing, and small punch testing. The hydrogen embrittlement (HE) indices obtained from conventional smooth and notched tensile specimens fall well below the 0.90 safety threshold specified in CHMC 1-2014, confirming that the studied material with a martensitic–bainitic microstructure is severely embrittled. Susceptibility grades derived from the disk burst test, predominantly exceeding a value of 2.0, closely align with those from the conventional tension-based methods, further indicating severe hydrogen embrittlement susceptibility. The HE index obtained from the small punch test (SPT) represented by the ratio of absorbed energy in 10 MPa H₂ to that in ambient air, was approximately 0.31 consistent with literature values (0.30–0.35) reported for severely embrittled steels. The study established a threshold HE index of 0.30 for the SPT methodology, in parallel with acceptance limits established in CHMC 1-2014 and ISO 11114-4 standards. A detailed comparison of the strengths and limitations of each testing method was also conducted.