Influence of surface roughness on consecutively hydrogen absorption cycles in Ti–6Al–4V alloy

In the present work the influence of roughness of the material surface with hydrogen absorption in Ti–6Al–4V alloy during four hydrogenated cycles is studied. The Ti–6Al–4V alloy samples were hydrogenated during several cycles at 650 °C for two hours, in 50% hydrogen and 50% argon atmospheres, 1 atm pressure and a flux of 50 cm3/min each one. The hydrogen concentrations are measured using Elastic Recoil Detection Analysis technique; meanwhile the roughness is measured using an Atomic Force Microscope. X-ray Diffraction analysis shows changes in crystal orientation due to hydrogen absorption. The hydrogen capacity of the Ti–6Al–4V alloy is observed to be directly correlated to the surface quality of the sample during the first hydrogenation cycles, but in the fourth cycle, the hydrogen absorption is almost equal for all the samples independently of their surface roughness.