Influence of bias voltage on the tribological properties of titanium nitride films fabricated by dynamic plasma ion implantation/deposition

Dynamic plasma ion implantation/deposition (PIID) combining gas and metal plasmas has been proven to be an effective technique to fabricate titanium nitride films. Pulsed vacuum arc and simultaneous substrate biasing can provide the capability to optimize film properties through flexible matching of processing parameters. In this work, titanium nitride films were synthesized on AISI304 stainless steel samples using filtered titanium cathodic arc and hot filament glow discharge. The effects of the substrate bias (8, 16 and 23 kV) on the tribological properties were investigated. The bias voltage has a slight influence on the film thickness and friction coefficient. The pin-on-disk experimental results demonstrate that a higher bias voltage (e.g. 23 kV) leads to better tribological properties compared to a lower bias. Under our testing conditions, the slide time to result in rapid friction increase for the 23 kV sample is 1.25 times that of the 8 kV sample. The wear tracks on the 23 kV sample are more irregular than those on the untreated or 8 kV sample. The improvement is believed to be related to the higher adhesion induced by ion mixing and formation of the surface layer incorporating titanium, nitrogen, and oxygen.