Study of hydrogen diffusion and trapping in 42CrMo4 quenched and tempered steel

摘要

There are many practical situations where steel components must provide a safe and reliable service during its entire lifetime working in contact with hydrogen generating environments or particular industrial processes. Some typical situations are corrosion phenomena, cathodic protection, welding, scouring, electroplating, etc.In this context, the aim of this work is to study hydrogen diffusion and trapping of quenched and tempered 42CrMo4 steel. First of all, the optimal conditions for hydrogen permeation tests have been thoroughly studied. Next, hydrogen permeation tests were performed at room temperature using a Devanathan-Stachurski cell in order to determine the hydrogen diffusion coefficient of the studied steel grades. Additionally, thermal desorption analysis (TDA) was employed to determine the amount of hydrogen introduced in the steel during the permeation tests and also to estimate the trap activation energies of hydrogen in the different microstructural traps. Finally, the study was complemented by microstructural characterization using SEM and TEM, which helped to better understand the interaction between hydrogen and microstructural traps.In general terms, the results obtained from permeation tests show that hydrogen solubility and trapping tends to increase with the steel hardness and that the evolution of the diffusion coefficient follows the opposite behaviour. Additionally, the main trapping sites of these microstructures were identified, and their characteristic trap activation energies were determined.