Effect of nanoparticles as lubricant additives on friction and wear behavior of tetrahedral amorphous carbon (ta-C) coating

As diamond like carbon (DLC) coating becomes increasingly popular in providing low friction and wear under lubricated conditions, the effect of various oil additives on tribological behavior of DLC coating is drawing more attention. Various oil additives, such as ZnDTP and MoDTC, have been widely used in automobile engine industry to pursuit excellent tribological performance in the insufficient lubrication condition. Although such commercial oil additives have been proven to reduce friction or/and wear to some extent, usage of such high -SAPS (sulphuric ash, phosphor, sulfphur) conventional additives is bound to arouse concerns due to environmental reasons. In this research, we investigate the effect of two nanoparticle oil additives, which are cerium oxide (CeO2) and zirconium dioxide (ZrO2), on friction and wear of non-hydrogen tetrahedral amorphous carbon (ta-C) coating. The results show that by adding ZrO2 nanoparticle, the friction of DLC coating could be reduced about 32% compared to non-additive base oil scenario, but specific wear rate increases by 40%. When CeO2 nanoparticle is used, friction increases by 22% compared to non-additive base oil scenario, however wear decreases by nearly 77%