Hydrogen-Induced Phase Transformations in Thin Specimens of an Austenitic Stainless Steel

Abstract

Cathodic hydrogen charging is a commonly applied experimental technique when hydrogen effects in austenitic stainless steels are studied. The interpretation of the experimental results is, however, complicated due to effects of changing stress state and hydrogen concentration in thin surface layers. It is generally accepted that dissolved hydrogen expands the austenite lattice, stabilizes hexagonal structure relative to austenite and results in martensitic transformations (1 – 3). In addition to martensitic phases also metastable hydrogen-rich phases have been reported to form in electrochemically hydrogen charged stainless steels. Crystallographically the hydrogen-induced martensitic structures seem to resemble those of known stress- or strain-induced martensites (4 – 7) although only a few detailed mechanistic or morphological studies are available (8).