Effects of hydrogen on carbon and manganese containing steels at high temperature

Effets de l'hydrogène sur les aciers contenant carbone et manganèse à haute température

Abstract

Hydrogen promotes the decarburization of carbon containing alloys. However, our results show that manganese partially retains carbon in the substrate probably due to the formation of stable manganese containing carbides. The decarburization rate also depends upon the metallic structure : between 600 and 900°C, a two phase metal (ferrite + perlite or ferrite + austenite) leads to a linear weight loss kinetic regime limited by an interfacial reaction. Above 1000°C, the austenite structure induces a parabolic weight loss regime showing that the process is limited by the carbon diffusion in the alloy. The effect of hydrogen on pure iron, a carbon free specimen, leads us to conclude that iron swelling at 700°C is due to the di-hydrogen recombination from atomic hydrogen dissolved inside the substrate.