The Influence of Load on the Tribological Properties of a-C:H Based Super-lubricating Film in Vacuum Environment

The a-C:H-based films have attracted great attention because of its ability to achieve super-lubrication at macro-scale,resulting in broad application prospects.However,the tribological characteristics of a-C:H-based films are very sensitive to the test conditions.In this study the influence of a typical working condition,normal load,on the film's tribological properties,and the underlying mechanism were studied.A ball-disk friction test machine was used to conduct friction experiments on the film under different loads.The wear morphology and volume under different testing conditions were measured using an optical profilometer.Raman spectroscopy was used to reveal the carbon phase structure informa-tion at the wear scar.The results showed that with the increase of normal load,the conversion of sp³bond to sp²bond at the wear scar increased,and the degree of graphitization of sp²bond increased,the hydrogen consumption rate at the wear scar increased with increased normal load as well.In the super lubrication stage,the load showed very limited effect on the frictional performance of the film.The wear resistance of the film relied highly on the ultra-low friction coefficient.No ob-vious wear was observed in all working conditions during the super-lubrication stage.Once the super-lubrication stage ter-minated due to hydrogen efficiency,severe wear started to appear,resulting in much higher wear vote.