Structure and properties of titanium and the Ti-6Al-7Nb alloy after isothermal oxidation

The purpose of the study was to determine optimal oxidation parameters of titanium Grade 2 and Ti-6Al-7Nb alloy in order to obtain the best structural, mechanical and tribological characteristics of oxide layers. It has been shown that the morphology of oxide layers depends on the oxidation temperature and the continuity of layers increased as the oxidation temperature rose. The examinations of the phase composition after oxidation showed mainly the presence of TiO2 in the crystallographic form of rutile. The phase composition of oxidised Ti-6Al-7Nb alloy was more complex (rutile, anatase, NbO, alpha-Al2O3). Isothermal oxidation significantly increases the surface hardness of both titanium Grade 2 and Ti-6Al-7Nb alloy. Layers deposited on titanium Grade 2 were 6 times thicker compared to Ti-6Al-7Nb alloy. Tribological tests have shown that the presence of an oxide layer on the surface significantly improves poor tribological properties of titanium and Ti-6Al-7Nb alloy.