Characteristics of the tribological properties of oxide layers obtained via thermal oxidation on titanium Grade 2

Abstract

Thermal oxidation is an effective technique for modifying the surface of titanium and its alloys in order to improve their poor tribological properties. This paper presents the results of tests concerning titanium Grade 2 subjected to thermal oxidation at 600 ℃ and 700 ℃ for 72 h. The morphology of the surface of the formed oxide scale was determined. The surface of a specimen oxidised at 600 ℃ was unevenly covered by very fine oxide particles. Raising the temperature to 700 ℃ made it possible to cover the entire examined surface with an oxide layer. The obtained scale was characterised by the presence of large irregularly shaped agglomerated oxide particles. Tribological tests showed that the presence of an oxide layer on the surface of titanium significantly improved the resistance of the interacting tribological couple to sliding wear. The obtained 3D isometric images of the trace of wear showed that the formed traces differed in terms of width, depth and shape. It was shown that the area of the cross section of the trace of wear decreased as the temperature of thermal oxidation increased. Scanning electron microscopic observations of traces of wear formed following tribological interaction with an Al2O3 ball showed, in a non-oxidised specimen and a specimen oxidised at 600 ℃, the presence of alternating morphologically varied areas formed as a result of corrugation wear. The oxide layer obtained at 700 ℃ has the highest resistance to sliding wear and completely eliminates the adverse corrugation wear phenomenon.