Influence of high-pressure pure hydrogen environment on hydrogen embrittlement susceptibility of X80 pipeline steel welded joints

Objective  The study investigates the effect of high-pressure pure hydrogen environment on the hydrogen embrittlement susceptibility of X80 pipeline steel welded joints, providing a reference for the hydrogen blending welding process of natural gas pipelines.

Method By employing impact tests and slow strain rate tensile tests, combined with SEM fracture analysis and plasticity index calculation, the hydrogen embrittlement susceptibility of X80 pipeline steel welded joints in a 6.3 MPa high-pressure pure hydrogen environment was investigated.

Result Firstly, both the strength and plasticity index of the heat-affected zone and weld metal of X80 pipeline steel decreased in a 6.3 MPa pure hydrogen environment, demonstrating a certain susceptibility to hydrogen embrittlement. Secondly, the fracture surface of the specimens exhibited a transition from ductile to brittle fracture, characterized by cleavage facets along the fracture edges. Thirdly, calculation results of the plasticity index ratio and elongation reduction rate indicated that the weld metal exhibited higher hydrogen embrittlement susceptibility compared to the heat-affected zone in the 6.3 MPa pure hydrogen environment.

Conclusion The susceptibility of welded joints of X80 pipeline steel to hydrogen embrittlement significantly decreases in a 6.3 MPa high-pressure pure hydrogen environment, with lower section shrinkage, elongation, and tensile strength compared to atmospheric air environment.