Modification of Diamond-Like Carbon (DLC) to improve specific tribological characteristics for automotive steel components

Carbon-based materials play an important role in today's science and technology. Carbon is a very versatile element whose two most interesting allotropic forms are Diamond (sp3) and Graphite (sp2). This way, the DLC has consolidated all its applications in the automotive and mechanical sectors in general. The management of the sp3/sp2 ratio yields various types of DLC that enhance hardness, reduce friction, and improve the corrosion resistance of the steel component.

The demand for DLC coating on steel components for endothermic and hybrid engines (pins, valves, camshafts, gears) is constantly growing; DLC improves engine performance and reduces emissions into the atmosphere.

In this presentation, the DLC deposited using the hybrid PVD-PaCVD (Physical Vapor Deposition-Plasma-assisted Chemical Vapor Deposition) technology will be examined. The modification of the layers, their thicknesses, compositions, and the containment of surface defects enhance the layer's hardness, reduce friction, and increase its resistance to corrosion. These characteristics can therefore be measured using laboratory instruments such as a nanoindenter, a contact tribometer, and a salt spray chamber. The next step is the bench test to assess results closer to real conditions. After laboratory analysis and bench tests, the applications are presented in 3 case histories: the increase in abrasion resistance in injection pins, the reduction in the friction coefficient on rocker arms, and the improvement in corrosion resistance in bipolar plates.