Hydrogen-induced defects of AISI 316 stainless steel studied by variable energy Doppler broadening energy spectra

Hydrogen-induced defects of AISI 316 stainless steel were systemically investigated by measuring variable energy Doppler broadening energy spectra (DBES) of positron annihilation. Defect profiles of the S-parameter from DBES as a function of positron incident energy up to 30 keV (i.e. similar to1 mum depth) were analyzed. Experimental results showed that hydrogen damage between the surface and the bulk has a significant variation with depth, and strongly depends on the condition of hydrogen charging, i.e. current density and charging time. It has been suggested that the increase in the S-parameter near the surface after hydrogen charging mainly comes from the formation of hydrogen damage (voids); however, the increase in the S-parameter in the bulk after hydrogen charging mainly comes from the production of structural defects (dislocations). Defect densities induced due to hydrogen charging in some cases (e.g. dislocation density in the bulk) were estimated based on a simple trapping model. (C) 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.