Effect of O2 flow rate on the structure, wettability and tribo-mechanical behaviour of Zr-O-N thin films

Structural and tribo-mechanical properties of Zr-O-N films deposited by reactive magnetron sputtering in a mixture of Ar (flow rate = 80 sccm), N-2 (flow rate = 20 sccm) and O-2 with a varying flow rate of 0 to 12 sccm were investigated. The films were characterized using scanning electron microscopy, energy dispersive x-ray analysis, atomic force microscopy, nanoindentation and wear tests. Oxygen content have a significant effect on the microstructure, wettability, tribo-mechanical properties of Zr-O-N films. The Zr-O-N films showed a dense structure with a mixture of zirconium oxides and nitrides and the preferred orientation changed from (111) ZrN to (200) ZrN with increasing O-2 flow rate. The ZrON film, deposited at an oxygen flow rate of 10 sccm exhibited the highest contact angle (147 degrees), the highest hardness (27.1 GPa), the lowest friction coefficient (0.36) and the lowest wear rate (5.8 x 10-7 mm(3).Nm(-1)). The improvement in the tribological performance of the ZrON film deposited at 10 sccm is attributed to the improved hardness and increased H/E and H-3/E-2 ratios, due to the formation of a hard solid solution by the diffusion of oxygen.