Tribological Properties Of Metal Nitride Composite Films And Nano-multilayers Synthesized By Magnetron Sputtering

Owning to the high hardness, good oxidation resistance and many other excellent properties, transition metal nitride nano-composite and nano-multilayered films can improve performance of cutting tools and extend their life-spans, which would result in promising prospects in industrial application. Upon this, the present work is dedicated to improve the tribological properties of the films. Ti-Si-N naonocomposite films and Cr-W-N, Cr-Mo-N series films were fabricated through DC magnetron sputtering. Effects of deposition parameters on microstructure, adhesion strength and tribological properties were investigated to obtain the optimal deposition condition.Composite targets, with Si embedded in Ti targets, were used to deposit Ti-Si-N composite films while substrate temperature, bias and power density were constant. The microstructure, morphology of cross-section and surface, chemical component of composite films were characterized by X-ray diffraction (XRD), high-resolution transmission electron microscope (HRTEM), scanning electron microscope (SEM), atomic force microscope (AFM) and energy dispersive X-ray spectroscope (EDS) respectively. Scratch tests were applied to determine the adhesion strength of as-deposited films. The tribological behavior was investigated using a ball-on-disk tribometer in both vacuum and humid air. The relationship between microsturcture, morphology, properties and deposition pressure were also discussed. It was found that the composite structure of Ti-Si-N films, nanocrystalline TiN embedded in amorphous Si₃N₄ matrix, was confirmed in this work. The increasing deposition pressure resulted in the appearance of columnar structure, decrease in the film density, increase in the surface roughness, and deterioration of the adhesion strength and tribological properties. The addition of Si in the composite films could improve the tribological performance of the films.The Cr-W-N, Cr-Mo-N series films were also deposited by magnetron co-sputtering using pure metal targets. The variation of the structure was achieved by altering rotation velocity of the substrate holder. Microstructure and morphology of the films were characterized by XRD, SEM. Rockwell indenter and scratch tester were also applied to investigate the adhesion of the as-deposited films to the substrate. Tribological property was determined by ball-on-disk tribometer. It was found that both CrN and W₂N existed in Cr-W-N films. In Cr-Mo-N films, however, only CrN existed while the larger Mo atom occupied the position of Cr in CrN crystal as a substitutional atom. The rotation velocity hadgreat influence on structure and properties of the films. The films existed as multilayers when the rotation velocity was no more than 2 rpm. With increasing velocity, the structure transformed to composite films. The optimal adhesion and tribological properties were achieved at 2 rpm which corresponded to the modulation period of 12 nm.