Oxidation behaviour of TiSiN(Ag) films deposited by high power impulse magnetron sputtering

Abstract

TiSiN coatings alloyed with increasing silver content were deposited for designing a self-lubricant coating with controlled lubricant element diffusion. Here, we report the influence of the Ag content on the oxidation behaviour of TiSiN(Ag) films deposited by HiPIMS (High Power Impulse Magnetron Sputtering) working in DOMS (Deep Oscillation Magnetron Sputtering) mode. In-situ high-temperature oxidation X-ray diffractograms allowed to observe the first signs of oxidation occurring at about ~ 850 °C with the appearance of the rutile TiO2 peaks. Observation of even distribution of silver was still possible on the un-oxidized part of the films, suggesting that the films offer an efficient barrier to the Ag diffusion. Dynamic-mode thermogravimetry analysis showed that silver addition does not change the onset point of oxidation of the coatings. However, the oxidation rate deteriorated with the presence of Ag. An unusual mass loss could be observed for the coatings with 6 and 10 at.% of Ag, as a result of silver evaporation/sublimation process. Results from isothermal thermogravimetry performed at 900 °C show two distinct regimes and corroborate the detrimental effect of the Ag on the oxidation resistance of the coatings. Nonetheless, in the un-oxidized part of the films, the silver continued to be homogeneously distributed confirming again the efficient barrier against Ag diffusion.