First-principles assessment of hydrogen absorption into FeAl and Fe₃Si: Towards prevention of steel embrittlement

We characterize the ability of two potential surface alloys, FeAl and Fe₃Si, to prevent H incorporation into steel, with a view toward inhibiting steel embrittlement. Periodic density functional theory calculations within the generalized gradient approximation are used to evaluate H dissolution energetics and the kinetics of H diffusion into and through FeAl and Fe₃Si. We predict increased dissolution endothermicities and diffusion barriers in both alloys compared to bulk Fe. Fe₃Si is predicted to be the most effective at inhibiting H incorporation, with a 1.91 eV [0.97 eV] surface-to-subsurface diffusion barrier on the (1 1 0) surface [(1 0 0 surface)] and a 0.79 eV endothermicity to bulk dissolution, compared to a 1.02 eV [0.38 eV] barrier and 0.20 eV dissolution energy in pure Fe [37]. We therefore propose that a thin layer of Fe₃Si may provide protection against H embrittlement of the underlying steel.