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.