Experimental and theoretical studies of growth mechanisms of hard wear-resistant carbon-based films on three-dimensional substrates

Abstract The deposition study, on three-dimensional substrates, of hard amorphous carbon films (DLC) for tribological applications is the aim of this work. In order to improve their performances (in particular adhesion) hard titanium-based sublayers (TiN, Ti(C,N) and TiC) have been deposited by ion plating. DLC films have been obtained by a PECVD process by decomposition of benzene in the glow region of a DC discharge. The different layers are deposited in the same run. To improve the homogeneity of the different properties on the substrates, their rotation is necessary. In order to understand the influence of this rotation motion and to point out the growth mechanism model of the different layers, three series of experiments were carried out. In a first step, coatings were realized on flat motionless substrates, making different angles with the deposition chamber axis. In a second step, a rotating shutter placed between the substrates and the evaporation source allowed modulation of the flux of particles impinging on the growing film. Finally, a parallelepipedic substrate was used to simulate a three-dimensional substrate. Properties such as deposition rate, density, adhesion and wear resistance are characterized. The influence of sharp edges is analysed in correlation with the ion current density on the substrate. A growth mechanisms model taking into account the role of the ions and that of the neutral is proposed to interpret the properties of the DLC films. The conditions needed to obtain DLC films with an excellent adhesion are pointed out. Adhesion is limited by that of the TiN underlayer on the steel substrate.