Hydrogen occlusivity and embrittlement in iron – effect of grain structure and cold work

Experiments have shown that the amount of hydrogen occluded in iron for a given charging condition depends on both the ferritic grain size and the nature of the grain boundaries. The larger the relative misorientation between grains, the higher the occlusivity per unit grain-boundary area. With increasing grain size of the same grain–boundary nature, the boundaries are saturated more quickly, and thus the susceptibility to hydrogen damage is higher. In general, cold working increases the hydrogen uptake by increasing the defect density. When stressed parallel to the deformation axis, specimens cold worked to 20% deformation were shown to have a reduced ductility loss after hydrogen charging, thought to be a result of the development of texture.