ANALYSIS OF THE HYDROGEN PERMEATION PROPERTIES OF TIN-TIC BILAYERS DEPOSITED ON MARTENSITIC STAINLESS-STEEL

The efficiency of TiN-TiC bilayer coatings, deposited by ion-beam-assi sted deposition on martensitic steel, as a hydrogen permeation barrier was investigated by a gas phase method; the hydrogen permeability in the TiN-TiC bilayers is very low, at least 10(4) times lower than in t he steel substrate in the temperature interval 470-570 K. Possible phy sical mechanisms, responsible for the reduced permeability of the cera mic bilayers, are discussed. In particular, from our experimental resu lts, it can be concluded that chemisorption and/or hydrogen jumping fr om surface sites to the first subsurface atomic layer represents the h ydrogen permeation limiting process.