Tribological and deformation behaviour of titanium coating under different sliding contact conditions

Titanium (Ti) coatings are widely used in biomedical engineering, microelectronics and thin film industry. However, very little is known about its tribological behaviour under dynamic contact conditions. In the light of this, the present work attempts to explore the tribological properties of a micrometer thick Ti coating deposited on a D9 steel substrate. Frictional tests were carried out using a tribometer in linear reciprocating mode against steel, alumina and silicon nitride balls. Three different loads of 1, 3 and 9 N at sliding speeds of 0.1, 0.5 and 2 cm/s were used to induce different contact conditions. Wear was calculated in terms of wear rate. Resulted tribo tracks were analysed using optical microscopy, scanning electron microscopy and Raman spectroscopy. Distinct deformation behaviours were observed which led to the formation of different kind of wear debris as revealed by SEM observations. The coefficient of friction was found to decrease with increase in speed but opposite trend was observed with increase in load with all the mating partners used. Wear rates were found to increase with corresponding increase in load and speed. Highest wear rates were observed in case of alumina ball and lowest were observed in case of silicon nitride ball. These observations have significant bearing while using Ti coating for wear resistant applications.