The diffusivity of H at room temperature in the ultra-high strength steel was studied by using electrochemical methods, sub-surface microhardness profiling, quantitative depth profiling using nuclear reaction analysis and nanohardness profiling. The samples were cathodically charged, under galvanostatic conditions, using a current density of 10A/m2. The electrochemical technique was used to determine the diffusivity of H, in the Aermet 100 cathode, by monitoring the potential as a function of time. These results were compared with diffusivity data deduced from sub-surface microhardness profiles. Independent nanohardness depth profiling was carried out in order to check hardness data near to the surface. An excellent correlation was found between the data for H diffusivity deduced from each of the techniques. The room-temperature H diffusivity was estimated to be about 2.91 x 10-13m2/s. Nuclear reaction analysis indicated that the near-surface concentration of H under electrolytic charging conditions was about 5at%.

Hydrogen Diffusivity in Aermet® 100 at Room Temperature under Galvanostatic Charging Conditions. P.A.Sundaram, D.K.Marble: Journal of Alloys and Compounds, 2003, 360[1-2], 90-7