Abstract
Hydrogen assisted crack growth of austenitic stainless steel may be controlled by the content of hydrogen which diffuses to a crack tip fracture process zone. A numerical analysis was conducted to investigate the influence of temperature and stress levels on the hydrogen concentration at the crack tip. Since α' martensite is induced by the plastic strain around the crack tip in this steel, the variation of diffusion coefficient as a function of the plastic strain and temperature was taken into account for the analysis. According to the analysis, the maximum hydrogen concentration was found occur at 60°C in SUS301 and at 32°C in SUS304, respectively. Such a trend was observed for both the cases of internal and external hydrogen. It was found that hydrogen accumulated in the process zone ahead of the crack tip when the volume fraction of martensite was high in the process zone and it was low enough in the surrounding area of the process zone. The hydrogen concentration at the crack tip was found to decrease, when the process zone size increased over the diffusion distance of hydrogen. All the results were consistent with the experimental results of crack growth test under cyclic loading.
