Microstructure, adhesion and tribological behaviors of Si interlayer/Si doping diamond-like carbon film developed on nitrile butadiene rubber

Abstract

Si doping diamond-like carbon (Si-DLC) films were prepared on NBR (nitrile-butadiene rubber) in order to improve its friction and wear resistance. Prior to the Si-DLC film deposition, a Si layer was firstly deposited on NBR as an interlayer, and the influence of the Si interlayer thickness on the microstructure, adhesion and tribological behavior of the films on the NBR and Si wafer substrates were systematically compared. The results showed that the surface morphology of the Si-DLC top layer on NBR exhibits a fractured morphology (crack-like network), and all Si-DLC films were characterized by a dense columnar-free microstructure. The deposition rate of films on NBR is faster than that of films on Si wafer. Furthermore, the highest ID/IG ratio and G peak position (sp2 content) could be obtained by the introduction of Si interlayer with a proper thickness of ~1.04 μm, which effectively relieves the compressive stress and thus significantly enhances the adhesion strength between film and NBR, and guarantees an excellent tribological performance. The lowest friction coefficient was achieved (~0.23 compared to 0.27 for the film without Si interlayer and 0.87 for the original NBR) under the relatively high load of 3 N. Meanwhile, the brittle fracture of Si-DLC films on NBR is one of the main factors leading to its lubricating failure under a high load, which suggests that it is necessary to deposit an interlayer to enhance the adhesion and the load-bearing capacity of the film (reducing its hysteresis), and to apply the different element doping and multi-layer composite structures to improve the toughness of the film.