Mechanical and Tribological Properties of TiCxOy Thin Films

Abstract

The main purpose of this work consists on the preparation of single layered titanium oxycarbide, TiC_xO_y, thin films, deposited by d.c. reactive magnetron sputtering. The depositions were carried out from a TiC solid target, on (AISI M2) steel substrates at 200 ^oC, under the variation of two process parameters, such us time deposition and flow rate of reactive gas O₂. The O₂ flow varied between 0.5 and 7.5 sccm and the deposition time between 3600 and 6000 s. In terms of film colours, the most interesting colour tones have been observed if the oxygen flow increased. Static friction coefficient, wear and residual stresses are characterized and discussed as a function of both process parameters (oxygen flow and time). The results reveled a good correlation between compressive residual stress level in the films and the oxygen flow. A compressive residual stress state has been observed if the O₂ flow is bigger than 1 sccm. Generally, the addition of oxygen till 7.5 sccm leads to an increasing of this compressive stress level to -17.7 GPa. For an oxygen flow rate higher than 2 sccm and a high compressive residual stress level, the deposited films presented a good wear behaviour. However, the best wear results were registered for a moderate value of the residual stress (-1.18 GPa) and an oxygen flow rate of 2.5 sccm.