Modeling of Hydrogen Diffusion Behavior Considering the Microstructure of Duplex Stainless Steel Weld Metal

抄録

Hydrogen induced cracking is usually evaluated by totally charged hydrogen concentration and macroscopically applied stress. However, microscopic distributions of stress and hydrogen concentration should be formed at the scale of microstructure. The stress concentration and hydrogen accumulation would be remarkable in duplex stainless steels and its welds, because they usually consist of ferritic and austenitic phases with different strength and diffusion properties. In this study, the effect of microstructure in duplex stainless steel on hydrogen diffusion behavior was investigated as a first step toward the evaluation of hydrogen induced fracture at microscopic scale. A series of finite element simulations have been performed under microstructure models considering duplex stainless steels and its weld metals. The hydrogen diffusion behavior was strongly influenced by the continuity of austenite phases which have lower diffusion constant compared to ferrite phases. The diffusible hydrogen accumulated to the location where stress concentration occurred due to microscopically different mechanical properties, however, the effect of stress concentration at microscopic scale was not significant for the overall diffusion behavior when the stress gradient at macroscopic scale was relatively small.