A Concept for Development of Hydrogen-Resistant Austenitic Steels

Austenitic steels represent a promising class of engineering materials for hydrogen use in vehicles, e.g. for tanks and pipelines. This topic is analyzed in terms of the effect of alloying elements on the interatomic bonds in the solid solutions and, consequently, on the interaction between hydrogen atoms and dislocations and hydrogen embrittlement, HE. The effect of Cr, Ni, Mn, Mo, Si, Al, Cu, C, N was studied. It is shown that the physical reason for HE amounts to the hydrogen-caused increase in the concentration of free electrons in the austenitic solid solution. For this reason, the alloying with elements decreasing the concentration of free electrons is expected to improve resistance of austenitic steels to HE. Alloying with Cr, Mn, Mo and Si is shown to be useful, whereas Cu, Al, Ni, N assist hydrogen degradation. The role of Ni amounts only to stabilization of the fcc austenitic lattice and its absence or the decrease of its content in steel is desirable. Based on the obtained results, recommendations are made for design of austenitic steels with increased hydrogen resistance.