Effect of microstructure on the hydrogen embrittlement, diffusion, and uptake of dual-phase low alloy steels with varying ferrite-martensite ratios

This study investigates the microstructure-dependent hydrogen transport properties and hydrogen embrittlement (HE) resistance of dual-phase (DP) ferritic-martensitic low alloy steels (LASs) for hydrogen-related applications. Ferritic-pearlitic and fully martensitic microstructures were also included as control conditions. Our results demonstrate that tempering DP-LAS reduces hardness and enhances carbide precipitation, leading to increased hydrogen diffusion coefficients and reduced hydrogen trapping. This effect is believed to be primarily associated with dislocation annihilation. Additionally, higher martensite content decreases the hydrogen diffusion coefficient in both as-quenched and tempered conditions. In slow strain rate tests, DP-LASs samples with approximately 50% tempered martensite exhibited the highest HE resistance. These findings offer new insights into the microstructure design of DP-LASs for hydrogen applications, particularly in the tempered condition.