Effect of nitrogen content on mechanical properties and tribological behaviors of hydrogenated amorphous carbon films prepared by ion beam assisted chemical vapor deposition

Abstract

In the present study, hydrogenated amorphous carbon (a-C:H) films with different atomic concentrations of nitrogen were prepared by differing the volume fraction of the nitrogen in the (N 2+C 2H 2) gas mixture during the deposition process. The characteristics of the coating films exhibited in terms of the chemical bond and bonding style, the surface topography, the material mechanical properties and the tribological behaviors were evaluated by a variety of experiments in order to examine the effect of the nitrogen content in the coating films. The experimental results indicate that the increase on the volume fraction of nitrogen in the gas mixture of (N 2+C 2H 2) would decrease the index of refraction but increase the extinction coefficient of the coating film. We found that the addition of nitrogen to the coating film lowers the nanohardness, irrespective of the content. A film with a relatively small internal stress can be produced by increasing the volume fraction of nitrogen in the gas mixture. The critical load for the coating layer to spall from the substrate is lower in a specimen having a high average internal stress. The endurance time in the friction and wear test is increased in the film that has a high nitrogen content.