Using the energy recoil detection analysis technique, hydrogen close to the surface of ion nitrided AISI steel M2 was studied. A surface hydrogen peak was observed in all samples, with or without exposure to the glow discharge. Some bulk hydrogen was also measured in all cases
its distribution was dependent on the history of the sample. The effect of the glow discharge is to drive part of the surface hydrogen into the bulk, depending on the treatment time. No obvious correlation with previously measured nitrogen profiles or microhardness profiles was found. (C) 1993 The Institute of Materials.