Screening of diamond-like carbon coatings in search of a prospective solid lubricant suitable for both atmosphere and high vacuum applications

The tribological performance of three types of amorphous carbon coatings was screened in search of potential candidates for solid lubricants suitable for working under both atmospheric and vacuum conditions. A coating obtained through ion assisted condensation of silicon oil vapours behaved well under atmosphere but failed in vacuum. Two types of hydrogenated amorphous carbon coatings, with and without Si doping, obtained by physical vapour deposition showed good performance in vacuum reaching superlow friction. The Si-doped amorphous carbon coatings were likewise good under atmospheric conditions with the coefficient of friction ranged between 0.1 and 0.15. The degradation of the coatings under vacuum was further studied using Mechanically Stimulated Gas Emission Mass-Spectrometry and Fourier-Transformed Infra-Red Spectrometry.