Effect of the alloying elements in TiN sublayer on the structure and mechanical properties of carbon coatings

Abstract

Amorphous carbon (a-C) coatings have numerous practical applications as antifriction or hard coatings. However, they are incredibly fragile and not compatible with many substrates. Therefore it is necessary to manage and improve the mechanical properties of a-C coatings, which depend on the properties and composition of the intermediate sublayer deposited between the substrate and coating. In this study, we proposed to control the structural and phase composition and, therefore, properties and practical applicability of a-C coatings deposited by pulsed cathodic arc by altering the chemical composition of the titanium nitride (TiN) sublayer deposited by direct current arc evaporation. We studied the effect of highly reactive and chemically neutral alloying elements on the coating structure and properties using aluminum and copper as typical examples. The results of Raman and X-ray photoelectron spectroscopies, atomic force microscopy, and mechanical testings suggested that highly reactive alloying elements led to an increase of the hardness and elastic modulus of the bilayered coating while alloying with copper resulted in a reduced friction coefficient. We also demonstrated that the introduction of aluminum in TiN sublayers increased the strength of the bilayer coatings and the crack resistance of the upper a-C layer. As a result, we achieved a significant level of control of the mechanical properties of the a-C coatings, which could be of interest in mechanical engineering or metallurgy for targeted control of the surface properties of products through the application of these coatings with expected and controllable mechanical properties.