Fracture of TiC/a-C(:H) coatings in friction contact

Abstract

Carbon-based coatings have excellent mechanical, electrical, and chemical properties. The tribological performance of these compounds is difficult to predict as it depends on a nonlinear interaction of different parameters as testing conditions, surrounding atmosphere, nature of the counterfaces, and film properties, so that a careful study of the structure–properties correlation is needed. This study is focused on the difference in tribological properties and fracture of the coatings, which are designed using two different types of a magnetron sputtering technology: high power impulse (HiPIMS) (pulsed) and direct current (DC) (non-pulsed). The work includes friction tests, calculation of internal stresses and microscopic study of the sample surfaces before and after friction, and analysis of chemical composition of surface layers and wear particles. The difference in friction and wear mechanisms depending on the applied technique is analyzed. The results showed that friction coefficient against 100Cr6 balls and internal stresses are greater for DC coatings, although they have a better resistance to brittle crack formation.