Microstructure and tribological behavior in ta-C films prepared by laser-induced filtered cathodic vacuum arc technique: Effect of charge voltage

Abstract

As an important power supply parameter, charge voltage has a significant influence on the properties of deposited films. In this work, the ta-C films were fabricated by the laser-induced filtered cathodic vacuum arc technique (LI-FCVA). The effect of charge voltage on microstructure, mechanical and tribological properties of ta-C films was investigated. Although macro-particles with various sizes were clearly visible on surfaces of films, the surface roughness was declined with increase of charge voltage. The sp3-C bond ratio in films was closely dependent on the charge voltage. At 160 V charge voltage, the sp3-C bond ratio was 54.1 %, then reaching to 61.2 % at the charge voltage of 190 V. With further increasing to 250 V, the sp3-C ratio slowly down to 57.1 %. This is ascribed to the change in energy for incident carbon ions which governed by the charge voltage. The highest hardness value, 54.5 ± 2.1 GPa, was obtained at the 190 V charge voltage, which was due to the high sp3-C content and relatively high residual stress. Similarly, the film deposited at 190 V possessed both low coefficient of friction (COF) and wear rate under various load, indicating that the excellent tribological performance of film could be achieved at 190 V. In addition, the COFs for all films decreased with an increase of load. The present work revealed that the moderate charge voltage value is beneficial for the enhanced wear property of film.