Fabrication, microstructure and tribological behavior of pulsed laser deposited a-CNx/TiN multilayer films

a-CNx/TiN multilayer films were deposited onto high-speed steel substrates by pulsed laser ablation of graphite and Ti target alternately in nitrogen gas. The composition, morphology and microstructure of the films were characterized by energy dispersive X-ray spectroscopy (EDS), scanning electron microscopy (SEM), X-ray diffraction (XRD) and Raman spectroscopy. The tribological properties of the films in humid air were investigated using a ball-on-disk tribometer. The multilayer films consist of crystalline TiN, metallic Ti and amorphous CNx (a-CNx). With an increase in thickness ratio of CNx to bilayer, the hardness of multilayer film decreases, friction coefficient decreases from 0.26 to 0.135, and wear rate increases. The film with thickness ratio of CNx to bilayer of 0.47 exhibits a maximum hardness of 30 GPa and excellent wear rate of 2.5 × 10− 7 mm3 N− 1 m− 1. The formation of tribo-layer was observed at contact area of Si3N4 ball. The film undergoes the combined wear mechanism of abrasion wear and adhesion wear.