Evaluating solubility and diffusion coefficient of hydrogen in martensitic steel using computational mechanics

Engineering applications of high-strength martensitic steels have been limited because of concerns regarding delayed fracture. Recent experimental and theoretical studies revealed that the presence of mobile hydrogen moving toward cleavage crack surfaces in these steels plays an important role in delayed fracture. Although the accumulation rate of hydrogen is affected by its own concentration and diffusion coefficient, it is still unclear how these properties are influenced by varying carbon content in martensitic steel. In this study, we estimated the hydrogen accumulation rate in martensitic steel under different carbon contents (0.395 and 0.787 mass %) and temperatures (300, 700, and 1000 K) by calculating its hydrogen solubility and diffusion coefficient using computational methods such as the density functional theory, molecular dynamics simulation, and finite element method. Results revealed that the hydrogen accumulation rate tended to increase with the carbon content and vice versa. © 2020 The Society of Materials Science, Japan