Phase transformation of austenitic stainless steels as a result of cathodic hydrogen charging

The effects of cathodic hydrogen charging and aging on surface phase transformations were studied in solution treated and cold worked specimens of two austenitic stainless steels. Quantitative phase evaluation using an X-ray technique has shown that cathodic hydrogen charging and aging can result in a considerable amount of surface transformation toε andα ′ martensites. The extent of this surface transformation differs significantly from deformation-induced transformation at the same temperature, and abnormally high volume fractions ofε martensite are produced by the charging process. A minimum charging current density is necessary to induce transformation. In cold-worked samples, further surface transformation due to hydrogen charging and aging is inhibited by high volume fractions of pre-existing martensite. A. P. BENTLEY, formerly with the Department of Metallurgy and Materials Science, University of Cambridge