Improving the Friction-Wear Properties and Wettability of Titanium Through Microstructural Changes Induced by Laser...

In this study, a surface treatment of Ti grade 1 was carried out in air with the use of a Yb-fiber laser to increase the friction-wear properties tested in dry contact with α-Al₂O₃. The laser surface treated specimens clearly differ in their surface roughness and wettability, coefficient of friction and resistance to wear, compared to untreated specimens. The microstructure changes induced by laser treatment were investigated using confocal scanning electron microscopy with chemical composition analysis by energy-dispersive spectroscopy, and phase composition by X-ray spectroscopy. It was found that laser surface treatment caused the formation of titanium oxide layers with TiO₂ (rutile, anatase and brookite) as the main constituent, while in the subsurface areas a partial transformation of α-Ti to β-Ti or α'-Ti was thermally induced. Specimens containing β-Ti or α'-Ti in the subsurface area and anatase or brookite in the top layer were characterized by two times lower friction coefficient values and 10 times lower volume wear index Wv in comparison to untreated Ti grade 1. Results clearly confirmed the beneficial effect of laser surface treatment on friction-wear properties of Ti grade 1, but the selection of laser processing parameters was crucial both for resistance to abrasive wear and wettability.