Effect of surface contamination and pretreatment on the hydrogen diffusion into and out of titanium under plasma conditions

The hydriding of etched titanium samples in a DC discharge was investigated using in situ thermogravimetry. It is shown that clean samples become embrittled and desorb hydrogen, while oxygen-contaminated samples show a limited hydrogen absorption. Samples were also immersed in an RF hydrogen discharge, and the hydrogen absorption observed is correlated with the amount of oxygen and nitrogen present on the surface. X-ray photoelectron spectroscopy was used to study the chemical stability of nitride coatings in hydrogen plasma and the surface changes which appeared upon hydriding clean etched samples. (orig.)