Rolling direction dependent diffusion coefficients of hydrogen in ferritic steel by SDCM charging and SKP probing

Abstract

Surface potential mapping of ferritic steel loaded with hydrogen through scanning droplet cell microscopy was performed with scanning Kelvin probe showing a drop in measured contact potential difference on hydrogen loaded spot. Equipotential areas were defined and used for determination of hydrogen diffusion coefficient parallel and orthogonal to rolling direction, resulting in values of 1.75×10-7 cm2 s-1 and 3.51×10-7 cm2 s-1, respectively. By controlling atmosphere composition and humidity during consecutive Kelvin probe measurements, the influence of oxygen concentration on the hydrogen discharging process was investigated, revealing interaction between surface oxides and hydrogen.