Improvement of boundary lubrication properties of diamond-like carbon (DLC) films due to metal addition

The effects of added materials such as metals like titanium (Ti), molybdenum (Mo) and iron (Fe) diamond-like carbon (DLC) films on boundary lubrication and microtribological properties were investigated. The nanoindentation hardness and microwear resistance can be improved by adding the proper metal to DLC films, as evaluated by atomic force microscopy (AFM). Boundary lubrication properties of DLC films with metals are improved as comparing with DLC films without metal under lubricant with both MoDTC and ZDDP additives. Moreover, lower friction coefficient of μ=0.03 than carburized steel is exhibited with the appropriate quantity of Ti added. The tribochemical reactant was formed on the sliding surface of the Ti-containing DLC film like as carburized steel. Higher mechanical damping materials containing elements, such as Mo, Zn, P and S, formed tribochemical reactors as observed by X-ray photoemission spectroscopy (XPS) and AFM force modulation methods.