The formation of diamond like carbon on carbon steel using plasma of argon-liquified petrolium gas mixing

Abstract

Diamond like carbon (DLC) is very important materials for mechanical industryespeciallycutting tools, automotive and production machines components. Formation of DLC on metal surface usually use a mixture of hydrocarbon/Ar plasma, such as CH4/Ar, C2H6/Ar, and C2H4/Arplasma. These materials are expensive. Therefore, the aim of this study is to replace the hydrocarbon/Arwith the carbon source of LPG/Ar mixture because it is cheaper and easy to get in the market. The formation of DLC wasconducted by using home made DC plasma glow discharge device, and carbon sourceof LPG/Ar gasmixture with ratio 9:1. The formation was carried out with pressure variation of 1.4 mbar, 1.6 mbar, 1.8 mbar, 2 mbarand time variation of 2 hours, 3 hours, 4 hours, and 5 hours at constant temperature 400 °C. The DLC formation was analyzed byusing Vickers hardness test, wear test, corrosion test and microstructure test (SEM-EDS and XRD). The optimum hardness and wear resistance are 225.3 VHN and 1.7 × 10−8 mm2/kg, and this was achievedrespectively, at 1.6 mbar and a 4 hours. Meanwhile, the un-coated materials are 115.5 VHN and 1.4 × 10−7 mm2/kg. The results show that hardness and wear resistance increase ifcompared to the un-coated materials. The microstructure observed using SEM-EDS show that thickness of hard layer is about one 5 µm. From XRD analyzed show that the formed phase is Fe2C phase. Based on these results it is expected that the forming DLC can be applied for the machine components and can increase the life time and mechanical efficiency so that the operation is more efficient because the friction losses become smaller.