Preliminary study of the mechanical and tribological properties of diamond-like carbon films prepared on steel substrates by filtered cathodic vacuum arc deposition

Abstract

In the present work, hydrogen-free diamond-like carbon (DLC) films were prepared on AISI 440C steel substrates at room temperature by using a filtered cathodic vacuum arc (FCVA) deposition system combined with a metal vapour vacuum arc (MEVVA) ion source. In the early stage of the experiment, ion implantation was performed with the MEVVA source in order to create a carbon composition gradient in the surface of steel substrates to serve as the interface for subsequent DLC coating without the use of metallic interlayers. With the highly mixed interface, well-adherent DLC films of about 60 nm thickness could be obtained. The substrates were DC biased during deposition, which determines the ion energy impinging on the growing films. The mechanical and tribological properties of the films were investigated in detail in the present research. A variety of analytical techniques were used for characterization, such as Raman spectroscopy, atomic force microscopy (AFM), nano-indentation, and scratch testing. The tribological behaviour of the films were studied by a conventional ball-on-disk method at room temperature. By optimising the deposition conditions, DLC films with hardness∼20 GPa and friction coefficients lower than 0.1 against the Cr-steel ball were obtained. The friction coefficient was maintained for several thousand cycles of unlubricated sliding. In addition, the scratch and wear resistance was improved.