Mechanical properties and performance of magnetron-sputtered graded diamond-like carbon films with and without metal additions

Abstract

A specific gradient in the constitution and properties of the growing film can be used to improve the mechanical properties and performance of magnetron-sputtered carbon films up to a thickness of 10 μm. The films were deposited on polished WC hard metal inserts and on silicon substrates. Additional argon ion bombardment of the growing film, caused by the substrate bias voltage applied during deposition, could be applied to raise the film density and hardness. The metal additions to carbon films were achieved in a physical vapor deposition process by adding titanium carbide to graphite targets. In a series of basic experiments, the substrate bias voltage for the deposition of homogeneous pure carbon and titanium added films was varied between 0 and −800 V. Afterwards, both pure carbon films and carbon films with metal additions were deposited with a gradient based on the effect of increasing the substrate bias voltage. The resultant residual stress of these graded films grown at various substrate bias voltages could be reduced in comparison to conventionally sputtered films. The mechanical properties and performance, such as Vickers hardness, critical load of failure, friction coefficient and the residual stress of the pure carbon films and the films with added metal, deposited with and without this gradient, have been compared.