Abstract
Hydrogen embrittlement poses a significant challenge to the steel industry, particularly in pipeline applications. This study investigates the potential of surface alloying to minimize hydrogen penetration into steels. Gaseous permeation tests were conducted on disks of Fe and several binary Fe alloys, with the goal to study the effect of alloying on the diffusion properties of hydrogen. Atomic-scale simulations were performed in parallel to examine high-symmetry monocrystalline iron surfaces modified with various alloying elements. The outcome of both approaches was finally compared.
For this purpose, different alloys were lab cast and subsequently hot- and cold-rolled. The alloy compositions and heat treatments were chosen carefully as such that all materials have a clean ferrite microstructure with equiaxial grain sizes. This allowed to focus solely on the effects of alloying on the behavior of hydrogen, without possible influences of second phases. The disks were subjected to high hydrogen pressures at different temperatures in gaseous permeation experiments.
The computational approach combined density functional theory (DFT) and kinetic Monte Carlo (kMC) simulations. Our method uses DFT-calculated energy barriers as input for subsequent kMC simulations, enabling the modeling of time-dependent hydrogen flux from a gaseous reservoir into the surface. Our results provide a qualitative ranking of the effectiveness of different alloying elements in limiting hydrogen ingress at the steel surface.
Together, these findings offer valuable guidelines for the steel industry in designing hydrogen-resistant alloys.