Friction behaviour of Si-DLC/DLC multi layer films on steel substrate in water environment

Abstract The tribological properties of diamond-like carbon (DLC) films over-coated by various thicknesses of Si-doped layers were investigated in a water environment. The multi-layer DLC films were deposited on a stainless steel substrate by pulsed-bias CVD technique. A dependence of friction coefficients on thickness of the over-coated layer was not observed and the friction coefficients of the films showed a stable and low value of approximately less than 0.1. On the other hand, specific wear rates of the films and mating balls depended on the thickness of the layers. Furthermore, the films with thin layers (less than 0.1 μm) and a thick layer (over 0.34 μm) showed the rupture on wear tracks. It was concluded that the optimized thickness of the layer (0.16 μm) improved the rupture strength of film, and showed a low specific wear rate of film and mating ball. It was found that the optimization of the thickness of the over-coated layer was important in achieving good tribological properties of Si-DLC/DLC multi-layer films.