Tribological behavior of hydrogenated W-C/a-C:H coatings deposited by different sputtering techniques

Reference Presenter Authors
(Institution)
Abstract
09-016 Frantisek Lofaj Lofaj, F.(Institute of Materials Research of SAS); Klich, M.(Lodz University of Technology); Medved, D.(Institute of Materials Research of SAS); Kabatova, M.(Institute of Materials Research of SAS); Vana, D.(Slovak Techical University); Dobrovodsky, J.(Slovak Techical University);

Carbon based coatings create an extended family of coatings with wide range of mechanical and tribological properties resulting from their structure and composition. When doped by metals, e.g. W, nanocomposite structure with controlled hardness and reduced residual stresses can be obtained. Their mechanical as well as friction properties are determined by the excess of lubricious carbon provided by hydrocarbon gases (usually C2H2 or CH4) during reactive sputtering. The incorporation of hydrogen from hydrocarbons and/or intentionally added into the sputtering atmosphere offers additional way to influence friction behavior, especially in a humid air compared to dry air or vacuum. This work is devoted to the comparison of the effect of hydrogen on the hardness and friction behavior of W/a-C:H coatings with different contents of hydrogen prepared by reactive sputtering in Ar/C2H2+H2 atmosphere using three different techniques: direct current magnetron sputtering (DCMS), High Power Impulse Magnetron Sputtering (HiPIMS) and High Target Utilization Sputtering (HiTUS). The content of hydrogen in the coatings was determined by Elastic Recoil Detection Analysis (ERDA) and the friction behavior of the coatings was investigated in humid air, dry nitrogen and vacuum as a function of hydrogen content. The ERDA measurements showed that C2H2 addition into Ar atmosphere is more effective way of hydrogenation of carbon matrix than direct hydrogen additions but it is accompanied by significant hardness degradation due to increased carbon content. Hydrogen concentrations >20 at.% resulted in a decrease of the coefficient of friction below 0.25 in humid air and dry N2 but achieving superlubricity would require even higher level of hydrogenation.

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