The Influence of UV Laser Treatment on the Structure and Surface Properties of Ti–6Al–4V Titanium Alloy

We examined the influence of pulsed ultraviolet (UV) laser radiation on the microstructure, phase composition, and functional characteristics of surface layers of Ti–6Al–4V alloy. Laser treatment leads to significant changes in the phase composition of the alloy surface, where newly formed oxide phases (TiO2, TiO) are detected in addition to the main initial α- and β-phases of Ti. It is shown that UV laser treatment leads to an increase of nanohardness by 25–30%, an increase of roughness, and a significant increase in hydrophilicity. In the initial state, the average value of wetting contact angle is 80°, and it decreases to 9°–13° after UV laser treatment. It is shown that the observed changes are due to the saturation of surface layer with oxygen, the concentration of which increses to 12–20%. This saturation leads to the formation of oxide phases and with an increase in free surface energy. Futhermore, it alters the ratio of the surface energy components, resulting in a decrease in a dispersity and a significant increase in the polar component. Based on the research conducted, it is concluded that UV laser treatment is an effective method to change the surface structure of Ti–6Al–4V alloy, its morphology and properties.