2021 年 61 巻 4 号 p. 1236-1244
Duplex stainless steels and their deposited weld metal have ferrite and austenite microstructures with different material properties. In addition, the microstructure of the base metal and weld metal clearly differs, affecting hydrogen diffusion and accumulation, and hydrogen-induced cracking behavior at the microstructural scale. In this study, the influence of microstructure on hydrogen-induced cracking behavior of the duplex stainless-steel weld metal was investigated. Duplex stainless-steel weld metal specimens were prepared and slow strain rate tensile test was performed after hydrogen charging. Cracks were observed at the ferrite/austenite boundaries. A microstructure-based finite element simulation was performed to clarify the concentration distribution at the microstructural scale. A finite element model based on the cross-section of the microstructure was designed to calculate the stress and hydrogen concentration distribution. The simulation result showed that hydrogen accumulation occurred at the ferrite/austenite boundaries, which corresponded to the locations where cracks were observed. On the other hand, the hydrogen concentration at the accumulation site in the weld metal was lower than that in the base metal. Therefore, the influence of the phase fraction and stress–strain curves of the ferrite and austenite phases on the hydrogen concentration was investigated by the proposed numerical simulation. Both phase fraction and stress–strain curves significantly influenced the microscopic distribution of hydrogen concentration.
