Influence of Arc Current on Structure and Properties of the Super-Hard ta-C Film Deposited by Arc Ion Plating

Five groups of diamond-like carbon (DLC) films were deposited on cemented carbide substrates by arc ion plating (AIP) under different arc currents ranging from 30 A to 90 A, aimed at the preparation of the super-hard ta-C film. The influences of arc current on the phase structure, microstructure, carbon atoms bond, mechanical properties and friction behavior of DLC films were studied by various measurement tools, such as scanning electron microscope, Raman spectroscopy, X-ray photoelectron spectrometry, nanoindenter and ball-on-disk tribometer, respectively. The results indicate that when the arc current is the lowest at 30 A, the surface of DLC film is the most smooth and compact, and the number of large particles is the least. The minimal ratio ID/ IG and the maximum sp3 bond content are 0.87 and 64% at the arc current of 30 A, respectively. The ta-C film exhibits excellent performance including the highest hardness and modulus of 56.7 GPa and 721.1 GPa, respectively, the highest elastic recovery coefficient of 58.9% and the lowest friction coefficient of 0.073 while arc current is 30 A. However, the surface of the film becomes loose and porous, and the number of large particles on the surface increase with the increase of arc current. The ratio ID/IG increases and sp3 bond content decreases with increasing arc current. The hardness and modulus of DLC films decrease gradually, the ratio H/E changes slightly and H-3/E-2 decreases, and the friction coefficient increases with increasing arc current. In this work, to prepare super-hard tetrahedral amorphous ta-C films with an excellent performance by arc ion plating under the premise of optimal ion energy, it is necessary to control the deposition and growth of the films under a small ion flux, which requires a small arc current to achieve.