FE simulation of hydrogen diffusion in duplex stainless steel

• FE simulation of hydrogen (H) diffusion in duplex stainless steel is performed.
• Highest diffusion coefficient is found for model with elongated austenite phases.
• Diffusion rate for coarse and fine phases are similar when austenite is saturated.
• Embedded flaw and tensile stress causes 6–8 times increase in local H concentration.

ABAQUS FE simulations of hydrogen diffusion in duplex stainless steel have been performed. Three models with different ferrite–austenite configurations have been applied and the hydrogen diffusion and the hydrogen coefficient have been evaluated as a function of austenite phase size and shape and the calculated diffusion coefficients compared to literature. Hydrogen concentration due to stress and plastic strain close to an embedded flaw has also been evaluated. An important observation is that the simulations show that when the austenite phases are saturated with hydrogen there is no large difference in the overall diffusion rate between the small and large phased models, i.e. no influence of tortuosity is observed. The work clearly demonstrates that both microstructure and flaws will influence the hydrogen diffusion and the hydrogen concentration and hence, must be taken into account when evaluating the susceptibility of hydrogen stress cracking in duplex stainless steels.