A comparison between the tribological and mechanical properties of TiN and TiCN

Titanium nitride (TiN) and titanium carbonitride (TiCN) thin films possess properties such as high hardness and low friction coefficients which make them important coatings in tooling and cutting applications where their tribological properties are of interest. Previous authors have compared the tribological properties of TiN and TiCN coatings deposited using the cathodic are and electron beam techniques [1, 2]. This study extends the work by evaluating the tribological properties of TiN and TiCN deposited by magnetron sputtering. Titanium targets and nitrogen gas were used to deposit TiN. Acetylene was added when depositing TiCN. In both cases deposition took place to give film thicknesses of 1.5 mu m and 2.5 mu m. Film characterisation techniques used to evaluate the coating included glancing angle X-ray diffraction, scratch adhesion, Rockwell indentation, Knoop hardness and pin-on-disk tribometry. TiCN was found to have a superior wear resistance and friction coefficient compared to TiN. In order to improve the mechanical and tribological properties of the TiCN the carbon content in the coating was increased. This gave a higher hardness and a lower friction coefficient. The tribological properties of the TiN coating were also improved by sputtering a thin layer (similar to 200 nm) of MoS2 onto the surface. This caused a significant reduction in wear rate and friction coefficient.