Visco-Elastic Properties of Reactor on Diamond-Like Carbon Films in Boundary Lubrication

To improve the lubrication properties of DLC (Diamond-like Carbon) films, DLC films were deposited by adding additive materials such as titanium (Ti), iron (Fe), molybdenum (Mo) and titanium dioxide (TiO2) with using by magnetron sputtering, and its friction properties were evaluated by oscillation type scratch tester, and ball-on-disk type tribometer in oil lubricant. In the scratch test, it is found that the critical loads of ferrous and titanium containing DLC films were larger than DLC film without metal. Friction coefficient of DLC film without metal is nearly 0.10 when using oil lubrication containing MoDTC (molybdenum dithocarbamates). On the other hand, all materials containing DLC films show lower friction than DLC film without metal does. Especially, DLC film deposited with adding appropriate quantity of titanium exhibits a low friction coefficient μ = 0.03. In order to know mechanism of lower friction of titanium contained DLC film, the viscoelastic properties of sliding and no-sliding areas were evaluated by force modulation method of AFM (Atomic Force Microscopy). The viscoelastic properties of sliding areas increased as comparing with that of no-sliding areas. It is thought that reactor of lower friction have been formed in sliding track of titanium containing DLC films in oil lubrication containing MoDTC.