Enhancing hydrogen embrittlement resistance in ferritic–pearlitic pipeline steel through degenerate pearlite formation

Abstract

This study developed a microstructural design strategy to enhance the hydrogen embrittlement resistance of ferritic–pearlitic pipeline steels. Samples collected from the surface and mid-thickness (center) of a hot-rolled thick steel plate were found to contain similar phase fractions of ferrite and pearlite, but the surface sample exhibited a higher fraction of degenerate pearlite (DP) and a lower fraction of lamellar pearlite (LP) because it cooled faster. This provided the surface sample with superior hydrogen embrittlement resistance because the continuous ferrite–cementite interfaces in the LP phase likely promoted hydrogen localization, accelerated hydrogen-induced crack formation, and induced blistering. These results suggest that pipeline steels containing pearlite phases should favor a DP structure over an LP structure to ensure their long-term sustainability in hydrogen-rich environments.