Chromium–Carbon-Based Coatings with Different Types of Nanocomposite Structure Obtained by Magnetron Sputtering and Their Properties

A comparative investigation has been performed to estimate the effect of the structural state and phase composition on the functional properties (the duration of stable operation inherent in the coated frictional contact under the conditions of high contact pressure, as well as friction coefficient, mechanical properties, and adhesive strength) for two types of chromium–carbon coatings. The studies have been performed for the chromium-alloyed diamond-like carbon coatings (Cr-DLCs) obtained by means of reactive magnetron sputtering of chromium in acetylene–nitrogen gas mixtures, as well as for the coatings deposited by means of nonreactive magnetron sputtering of targets made of chromium and detonation nanodiamonds (NDs). It has been shown that the features of the nanocomposite structure inherent in these coatings can significantly affect the tribological and micromechanical behavior of the coatings. The adhesive strength testing by means of instrumented scratching with progressively increasing load on a moving diamond indenter have indicated the fact that the process of coating fracture exhibits a multi-stage character. The scratching damage types, their relationships with the structural state and phase composition of coatings, as well as threshold (critical) loads at which the character of coating failure changes have been found. It has been shown that there is a correlation between the content of carbon in chromium-carbon coatings, the tribological performance under the conditions of a heavy-loaded frictional contact and the adhesive strength characteristics. These results demonstrate that the tribological and other functional properties of chromium–carbon coatings with a nanocomposite structure can be controlled via changing microstructural state and phase composition by choosing appropriate technological parameters of a plasma-assisted vacuum deposition process.