Evolution and mechanism of hydrogen gas embrittlement susceptibility for X80 pipeline steel within the service temperature range

Abstract

The influence of temperature on the hydrogen gas embrittlement (HGE) susceptibility of X80 is unclear. In this work, mechanical test results revealed the enhanced HGE susceptibility with the decreasing temperature ranging from 333 K to 263 K. At lower temperatures, quasi-cleavage characteristics appeared on crack surfaces and plasticity suppression was further enhanced. Increased dislocation trapping capacity with decreasing temperature was demonstrated by finite element analysis and first-principles molecular dynamics calculations. At the investigated temperature, hydrogen could be sufficiently supplied to dislocations. Therefore, hydrogen trapping sites exhibited a higher concentration than lattice hydrogen and played a dominant role in determining the overall hydrogen distribution within the material. The strong trapping ability of dislocations at lower temperatures could increase the hydrogen concentration in high-density dislocation regions, including the crack tip. It recommends that the HGE of X80 for hydrogen delivery shall be evaluated at a lower temperature instead of room temperature which usually be used.