Enhanced hydrogen degradation of two pipeline steels by increasing inert gas pressure in hydrogen-containing mixtures: experimental and theoretical insights

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This study highlights the significant role of total gas pressure in enhancing hydrogen degradation in hydrogen/inert gas mixtures. Tests were performed to measure the fatigue crack growth rate (FCGR) of X80 and GB20# pipeline steels in pure hydrogen and hydrogen/nitrogen blends. Findings showed that FCGR increased in the blend with elevated total gas pressure relative to pure hydrogen, despite an equivalent hydrogen partial pressure between the two environments. First-principles molecular dynamics (FPMD) calculations revealed that the increased number of nitrogen molecules within the Fe-H2-N2 systems promoted the movement velocity of hydrogen and premature dissociation of hydrogen.