Abstract
High strength steels (HSS) are widely used in critical applications in the aerospace and automotive industry. However, these materials are highly susceptible to failures induced by hydrogen embrittlement (HE). Even though HE in HSS has been extensively studied throughout the years, the detailed mechanisms involved in hydrogen diffusion and segregation at different microstructural features are still insufficiently understood. Therefore, the aim of this study is to conduct a detailed microstructural characterization of a 300M HSS and relate this to hydrogen diffusion and trapping characteristics. Electrochemical permeation technique is used to investigate hydrogen diffusion and trapping on a thin membrane of the studied material. The build-up and decay of permeation transients are analyzed to obtain diffusion and trapping information. Results obtained with and without the addition of hydrogen recombination poison are compared. Diffusion and trapping data are then correlated with a detailed microstructural characterization performed by a novel technique using CFE-SEM (Cold Field Emission-SEM), which allows image spatial resolution of the same order of traditionally used TEM. The use of a CFE-SEM is advantageous mainly from sample preparation and statistics perspectives, as a bulk sample is examined instead of a thin foil.