Hydrogen diffusion and trapping in 42CrMo4 quenched and tempered steel: Influence of quenching temperature and plastic deformation

Medium- and high-strength steel components working in contact with hydrogen-rich environments must be appropriately designed in order to provide safe and reliable service during their entire lifespan. In this context, the present paper aims to study hydrogen diffusion and trapping in a quenched and tempered 42CrMo4 steel by means of electrochemical permeation methods. The effect of quenching from a high austenitizing temperature and applying a plastic deformation of 10% and 20%, were also evaluated. In general terms, the results showed that with increasing cathodic current (amount of hydrogen introduced in the steel specimen), the apparent hydrogen diffusion coefficient also increases up to a maximum constant value that corresponds to the lattice hydrogen diffusion coefficient, D-L. Quenching the steel from a high austenitizing temperature decreases hydrogen diffusivity and increases the density of traps. On the other hand, microstructural trapping increases (increase in the dislocation density) and the diffusion coefficients decrease after applying a cold plastic deformation. All the aforementioned modifications related to the permeation of hydrogen throughout the microstructure of the steel were finally correlated with changes in the steel's hardness.