TiCxOy thin films for decorative applications: Tribocorrosion mechanisms and synergism

Recently, tribocorrosion is widely accepted as an interdisciplinary area of research and such studies on various materials are gaining more attention by scientists and engineers due to its practical and economical significances in a wide range of applications. The main objective of the present work were to investigate the tribocorrosion behaviour of single layered titanium oxycarbide, TiCxOy, thin films on a reciprocating sliding tribometer, and in the presence of artificial sweat solution at room temperature, by considering the practical usage of such films as a decorative coating on various components.The films were produced by DC reactive magnetron sputtering, using C pellets incrusted in the Ti target erosion area. A gas atmosphere composed of Ar and O2 was used. The Ar flow was kept constant, and the oxygen gas flow varied from 0 to 10 sccm. During the wear tests both the open circuit potential and the corrosion current were monitored. Also, electrochemical impedance spectroscopy (EIS) tests were performed before and after sliding process. The modifications on the “native” coating microstructure and/or chemical composition induced by the variation of the deposition parameters were also evaluated and correlated with the wear–corrosion mechanisms occurring in each system.The corrosion studies, including EIS measurements, exhibited the high corrosion resistance of the TiCxOy films, which is clear from the unchanged/constant values of the polarization resistance, before and after the sliding process, at the evaluated potential. The effects of hardness, thickness and structure of the films on their tribocorrosion performance, as a function of oxygen fraction, were studied and an attempt was made to classify them. Two of the eight films (fO=0.55 and 0.79), considered in the test, demonstrated better tribocorrosion resistance than others. Further, individual and synergistic effects of wear and corrosion on total wear loss were estimated and correlated with tribocorrosion mechanisms.