The Formation of Diamond Like Carbon On Carbon Steel Using Plasma of Argon-Liquid Petrolium Gas Mixing

Diamond like carbon (DLC) is very important materials for mechanical industry especially cutting tools, automotive and production machines components. Formation of DLC on metal surface usually use a mixture of hydrocarbon/Ar plasma, such as Cl-14/Ar, C2HJAr, and C2HJAr plasma. These materials are expensive. Therefore, the aim of this study is to replace the hydrocarbon/Ar with the carbon source of LPG/Ar mixture because it is cheaper and easy to get in the market. The fonnation of DLC was done by using home made DC plasma glow discharge device, and carbon source of LPG/Ar gas mixture with ratio 9 : 1. The formation was carried out with pressure variation of 1.4 mbar, 1.6 mbar, 1.8 mbar, 2 mbar and time variation of 2 hours, 3 hours, 4 hours, and 5 hours at constant temperature 400 °C. The DLC formation was analyzed by using Vickers hardness test, wear test, corrosion test and microstructure test (SEM-EDS and XRD). The optimum hardness aod wear resistance are 225.3 VHN and 1.7 x 10"8 mm2/kg, respectively, at 1.6 mbar and a 4 hours. Meanwhile, the un-coated materials are 115.5 VHN and 1.4 x l 0·7 mm2/kg. The results show that hardness and wear resistance increase in compared to the un-coated. 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.