Notched-tensile properties under high-pressure gaseous hydrogen: Comparison of pipeline steel X70 and austenitic stainless type 304L, 316L steels

The effect of high-pressure gaseous H₂ on the fracture behavior of pipeline steel X70 and austenitic stainless steel type 304L and 316L was investigated by means of notched-tensile tests at 10 MPa H₂ gas and various test speed. The notch tensile strength of pipeline X70 steel and austenitic stainless steels were degraded by gaseous H₂, and the deterioration was accompanied by noticeable changes in fracture morphology. The loss of notch tensile strength of type 316L and X70 steels was comparable, but type 304L was more susceptible to hydrogen embrittlement than the others. In the X70 steel, hydrogen embrittlement increased as test speed decreased until the test speed reached 1.2 × 10^?3 mm/s, but the effect of test speed was not significant in 304L and 316L steels.