Numerical simulation of hydrogen diffusion in low alloy steel welded joint under wet H₂S environment

Hydrogen diffusion coefficients in weld metal, heat affected zone (HAZ) and base metal of the 16MnR low alloy steel welded joint were measured by electrochemical permeation technique. Based on finite element code-ABAQUS, the hydrogen diffusion in welded joint was numerically simulated. The effects of welding residual stress and microstructure on the hydrogen diffusion were taken into account. The variation of hydrogen concentration with time was obtained. The results show that the hydrogen diffusion coefficients and welding residual stress were much larger in weld metal and HAZ where the hydrogen accumulates, which can decrease the material properties and cause the cracking and damage related to hydrogen under wet H₂S environment.