First-Principles Evaluation of Alloying Effects on Hydrogen Adsorption and Trapping at Grain Boundaries in Pipeline Steels

Abstract

Hydrogen is a zero-emission energy carrier with significant potential for clean energy systems, making its safe and efficient transport essential. Transporting hydrogen through steel pipelines offers a cost-effective distribution method. However, hydrogen embrittlement poses a significant risk, leading to pipeline failure, and hydrogen uptake plays a critical role in this process. In this study, the influence of alloying elements at a ∑5(310)/[001] Fe grain boundary on hydrogen uptake is investigated using first-principles calculations. These elements were introduced at either the surface or bulk regions of the grain boundary at different concentrations. The results show that hydrogen dissociation is inevitable at the doped grain boundary, indicating that the alloyed grain boundary provides sufficient energy for H–H bond cleavage. On the surface, doped grain boundaries act as strong trapping sites for atomic hydrogen─especially in the presence of W, Ti, Ni, Mn, and Co at high concentrations, as supported by charge density analysis. In contrast, these boundaries act as weak trapping sites in the bulk, particularly at high alloying concentrations, due to the compressive strain induced in the grain boundary region. Overall, the findings suggest that alloyed grain boundaries do not serve as fast pathways for hydrogen uptake in pipeline steels.