Wear behavior of diamond-like carbon metal carbide multilayers

The high level of stress in hard diamond-like carbon (DLC) films limits their maximum thickness and their compliance with substrate deformation. Multilayer films are one approach to overcome these disadvantages. We have prepared multilayers of DLC/TiCx and DLC/WCx by filtered cathodic vacuum are, then investigated and compared their wear properties at room temperature. The films were deposited on polished, oil-hardened AISI 01 tool steel substrates. The number and thickness of layers within the films were varied while the total thickness was approximately constant. Friction coefficients and wear were measured as a function of the atmosphere and load in ball-on-disk tests. Tests were performed in dry nitrogen and in air with relative humidity of 50%. Initial Hertzian contact pressures of 0.8 and 1.4 GPa were used with alumina balls. For all films showing good wear resistance, both the layer in immediate contact with the steel and the topmost layer were DLC. The failure mechanism and the wear resistance were found to be highly dependent on the type of carbide, on the atmosphere during the wear test and on the thickness and number of individual layers. (C) 1998 Elsevier Science S.A. All rights reserved.