Abstract
In the automotive industry, hydrogen embrittlement is a major issue to tackle the development of steels with higher strength. The understanding of the mechanisms of hydrogen uptake and release is thus of primary importance. As hydrogen-containing sources are almost ubiquitous in any atmosphere, it remains quite difficult to identify the origin of hydrogen present in the material, as well as to quantify its amount firmly. In this regard, the use of deuterium, the hydrogen isotope with one more neutron, has proven to be a very effective strategy. Deuterium exhibits many advantages due its natural scarcity, enabling a right identification of its origin in the material and cleaner measurements.
If deuterium assets are undeniable, a specific care is however required when using it instead of, or combined with, hydrogen. Indeed, the main difference between both atoms remains in their atomic mass, which is twice larger for deuterium, and can affect several other properties. Consequently, even if they are isotopes, slight discrepancies called isotope effects can occur. Literature already highlighted isotope effects for properties such as the diffusion coefficient. When hydrogen and deuterium are simultaneously present in the atmosphere, exchanges can also occur between both isotopes to form hybrid molecules named HD, whose formation has to be considered.
In this context, this work focusses on the assessment of a specific methodology dedicated to systems where hydrogen and deuterium are used instead of each other. Peculiarly, this work aims at highlighting the influence of isotope effects on the hydrogen uptake mechanisms and on the quantification of hydrogen amount. For this purpose, bare 22MnB5 steel, which is a press-hardened steel commonly used in the automotive industry, was considered. Austenitization heat treatments in presence of hydrogen and/ or deuterium enabled to determine the isotope effect on their absorption by the material. Thermal desorption analysis then allowed to measure isotopes absorbed in the material and a dedicated methodology was built to adequately process the isotope measurements.