Stabilization of Austenite by Hydrogen

Abstract

ATTEMPTS to study the possible effects of hydrogen on the austentite–martensite transformation in steels have always to reckon with the difficulty of retaining adequate amounts of hydrogen in them, regardless of the amounts initially present. The austenitizing and heat treatment of steels are generally carried out at virtually atmospheric pressures or in vacuum. As the diffusion-rates of hydrogen at elevated temperatures are considerable, the amount of hydrogen retained in the austenite, prior to its being heat-treated, is generally small. It is also not so much in excess of the solubility limits as to render it likely that the hydrogen atoms play a part similar to that played by carbon atoms, which are generally retained in appreciable amounts and in a state of considerable supersaturation when the matrix changes to the body-centred structure. In the comparatively small amounts, therefore, in which hydrogen is retained in normally austenitized and heat-treated steels the likelihood of its affecting the stability of austenite may well be negligible (Ramachandran, E. G. and Dasarathy, C., unpublished work).