Hydrogen permeability tests were carried out in Inconel 690 in the as-received condition and after heat treating. The heat treatments promoted total solid solution or a microstructure full of grain boundary coverage with M23C6 carbides (A800). first and second polarization hydrogen transients were determined and used in disclosing the role of reversible and irreversible hydrogen trapping. It was found that in the solid solution condition, the permeation rates were the highest but they were significantly reduced in the as-received condition, particularly in the A800 due to the presence of grain boundary M23C6 carbides.

Microstructural Effects on the Hydrogen Permeation of an Inconel Alloy 690. J.M.Zagal, H.F.López, O.Flores, J.L.Albarran, L.Martínez: Corrosion Science, 2008, 50[12], 3371-7