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Herein, a numerical solution of Fick's second law in one dimension with experimentally determined diffusion coefficients at different constant loads is combined with slow strain rate tensile tests and subsequent fractography on dual-phase steel. From the latter, the depth of the hydrogen embrittled region is determined and correlated to concentration profiles determined by the numerical model. The concentration profiles indicate that incorporating stress dependency of the diffusion coefficient results in different concentration profiles compared to using a constant diffusivity. Additionally, these allow to more accurately determine a critical local hydrogen concentration based on the total diffusible hydrogen concentration at saturation.

This work evaluates the effect of hydrogen on the mechanical integrity of a weld in a martensitic base metal. Different regions in the heat-affected zone (HAZ) are reproduced to investigate the interaction of the local microstructure with hydrogen. The hardness strongly depends on the distance from the welding joint due to the different phases present. The HAZ contains zones of acicular ferrite, coarse martensite and tempered martensite. Additionally, the entire weld is subjected to a constant load while being simultaneously electrochemically charged with hydrogen. During this test, a crack initiates in the filler, showing the highest hydrogen solubility as demonstrated by thermal desorption spectroscopy, while propagation occurs along the microstructure of the HAZ with the highest hardness level.