Ti content on the tribological properties of W/Ti-doped diamond-like carbon film lubricating with additives

In this study, tungsten and titanium co-doped diamond-like carbon films (W/Ti-DLC) on the AISI 316 L stainless steel substrate with different currents of Ti target are deposited by ion beam deposition/DC magnetron sputtering technology, and Ti contents in the W/Ti-DLC films varies from 0 to 1.9 at. %. The mechanical properties, chemical composition and tribological properties of the W/Ti-DLC films are analyzed by nano-indentation instrument, scanning electron microscopy (SEM), Raman spectrometer, X-ray photoelectron spectroscopy (XPS). The friction and wear behaviors of the films versus AISI 52100 steel ball under molybdenum dialkyldithiocarbamate (MoDTC) and zinc dialkyldithiophosphate (ZDDP) containing lubrication conditions are investigated by using an SRV tribometer. The results show that doping Ti with high content can cause graphitization on the film surface. The variances of the coefficients of friction and wear rates of the films with Ti content under lubrications are mainly governed by the graphitization and tribofilms formed on the worn surfaces. MoDTC presents better friction reduction effect on the W/Ti-DLC film and Ti content has effect on the formation of ZDDP derived tribofilm.