Nanopore-assisted rapid Cr diffusion in irradiated additive-manufactured steel

Additively manufactured stainless steel exhibits different oxidation and corrosion properties compared with traditional counterparts. Molecular dynamics simulations were performed to systematically investigate Cr diffusion near nanopores, in order to elucidate the fast formation of dense oxidation layers in laser powder bed fusion processed 304L stainless steel after ion irradiation. The influence of pore diameter and temperature on Cr diffusion was studied in Fe simulation boxes with 1 at.% Cr and random nanometric pores. The results show that the existence of nanopores significantly accelerates Cr diffusion, facilitating the formation of oxide layers. While increasing with temperature, the diffusion coefficient does not increase uniformly with pore diameter. Regarding the nanopores with diameters of 4.82–13.25 Å, the diffusion coefficient of Cr in their vicinity is maximized at diameter of about 6 Å. The specific fast diffusion paths near the nanopores were exposed and discussed.