Effect of tempering temperature on stress-assisted hydrogen diffusion and hydrogen-induced embrittlement in a high strength low alloy steel

Abstract

Hydrogen can be used as a probe to detect defects created during tensile tests. Through hydrogen diffusion behavior investigated under two loading ways in a high strength low alloy steel tempered at three different temperatures, the mechanism of embrittlement resulted from dynamic hydrogen charging was elaborated. Before yielding, the stress has no significant effect on the hydrogen diffusivity. However, near yield stress, the hydrogen diffusion varies with sustaining the loaded time, while at the plastic region, the hydrogen diffusivity returns to a relative lower and stable value. In addition, hydrogen solubility monotonously increases with elastic stress in all samples tempered at different temperatures, whereas the plastic stress can differently alter the steady state hydrogen permeation flux from sample to sample depending on the tempering temperature. Hence, all samples tempered at different temperatures can be damaged in advance by dynamic hydrogen charging but the sensitivity to hydrogen embrittlement can still be alleviated by raising tempering temperature.