Very high-cycle fatigue behavior of steel in hydrogen environment: State of the art review and challenges

Global warming and extreme climate problems caused by the intensive exploitation of fossil fuels have become increasingly serious. With the urgent global demand for clean energy, green hydrogen energy has become one of the important directions for future energy transformation due to its zero carbon emissions and wide source. However, embrittlement occurs in almost all metals when exposed to hydrogen, which greatly hinders the development of the hydrogen energy industry. Furthermore, the key application terminals of hydrogen energy are found in engineering equipment for aerospace, civil engineering, transportation and other fields. These equipments must endure long life with high reliability operation requirements. Therefore, accurately evaluating their Very High Cycle Fatigue (VHCF) characteristics in a hydrogen environment is the key for the future advancement of the hydrogen energy industry. In this article, the latest related research on VHCF failure behavior and hydrogen embrittlement mechanisms are briefly reviewed. At the same time, this work focuses on the impact of hydrogen on VHCF behavior, with the aim to provide some guidance for the research on VHCF characteristics and the design of metal equipment in hydrogen environment. Finally, this review summarizes the current higher-level challenges of VHCF research in hydrogen environments and provides some potential tools that may further address these challenges.