Size effects of friction in pure titanium

Abstract

The article is devoted to an experimental study of the tribological behavior without lubrication of commercial pure titanium under specific conditions close to fretting, which differs from traditional tests by the small amplitude and frequency of indenter movement. Tribological characteristics: wear and the friction coefficient at room and elevated temperatures of Grade 4 titanium are compared in the ultrafine-grained (grain size dg = 0,45 μm) and coarse-grained state (dg = 45 μm). It has been shown that at room temperature, reducing the grain size by two orders of magnitude increases wear and the friction coefficient. Reducing the displacement amplitude from 300 to 50 μm brings the friction conditions closer to fretting and reduces both wear and friction coefficient. An increase in temperature from room temperature to 350°C transforms the traditional type of wear into the formation of an oxide film and reduces the friction coefficient. The boundary conditions for the occurrence of fretting and their applicability to nanostructures are discussed.

Keywords

• titanium
• ultrafine-grained structure
• wear
• friction
• fretting