Numerical study on effect of inclusions on hydrogen segregation in steel under stress conditions

It is generally believed that hydrogen embrittlement (HE) of metallic material is closely related to the presence of hydrogen traps such as inclusions inside. Therefore, the study of hydrogen segregation in the inclusions is essential for the further understanding of the mechanism of HE phenomena. In this study, a numerical model for exploring the hydrogen transport and hydrogen segregation in inclusions under stress conditions was developed, and the effect of inclusion's shape and orientation, micro-cracks and stress magnitude on hydrogen segregation was investigated. Results showed that, inclusion's shape made a great effect on the hydrogen concentration at the inclusions/matrix interface, which became higher as inclusion closed to a globular shape. The hydrogen concentration inside the inclusions was affected by both the shape of inclusions and the angle between the orientation of inclusions and the hydrogen diffusion direction. The hydrogen segregation in inclusions with micro-cracks was much greater than that without micro-cracks, which caused 3–4 times local hydrogen concentration increase in inclusions, leading to the enhancement of HE susceptibility of the steel. The magnitude of stress did not change the regions of hydrogen segregation, but the hydrogen concentration at each region increased with the increasing stress.