Effect of hydrogen on the tensile properties of 42CrMo4 steel quenched and tempered at different temperatures

Hydrogen solubility was seen to decrease with increasing tempering temperature. Moreover, hydrogen embrittlement measured in notched specimens was much greater in the grades with higher hardness, tempered at the lowest temperatures, where a change in the fracture micromechanism from ductile in the absence of hydrogen to intermediate and brittle in the presence of hydrogen was clearly observed. Results were discussed through FEM simulations of local stresses acting on the process zone.