Relationship of Morphology and Chemical Composition of the Surface of Doped Diamond-Like Coatings with the Friction Coefficient

The prospects for the use of diamond-like carbon coatings in tribology are largely associated with various technologies for their alloying. This paper presents a comprehensive technique for studying silicon-doped diamond-like coatings, including tests for friction in a pair with steel and analysis of the mechanisms of frictional interaction. Experimental samples of the coatings were obtained by plasma-enhanced chemical vapor deposition on a flat steel substrate. Tribological tests were carried out according to the ball–plane scheme with reciprocating motion and differed in the time of the experiment. The morphology and chemical composition of the initial surface and the surface after tibological tests of samples and counterbodies were studied using the methods of scanning electron and probe microscopy. The mechanisms of transformation of surface layers during friction and formation of a protective film of secondary structures on the surface were considered. The effect of these changes on the properties of frictional contact at different silicon content in carbon coatings has been established. The analysis of the influence of load parameters, test duration, and coating composition on the processes of formation of surface antifriction films and their destruction during friction is carried out. With an increase in the load, a decrease in the running-in duration is observed, however, at the same time, the duration of a stable low friction (with coefficient less than 0.1) stage decreases. It is shown that secondary structures, which contribute to a decrease in the coefficient of friction, cover a part of the working surface of the samples and are effective in short-term tests.