Tribological performance of nano-diamond composites-dispersed lubricants on commercial cylinder liner mating with CrN piston ring

This work investigated the effect of nanodiamond (ND) additives on the tribological properties of CrN-coated piston ring mating with the chromium-plated and BP alloy iron cylinder liners, which is one of the key friction pairs in the internal combustion engines. To enhance the dispersion of the NDs in the base oil, the surface of ND particles was modified with polyaniline via in situ polymerization. The friction and wear as well as the scuffing characteristics of the friction pair lubricated with different contents of ND composite-added base oil were evaluated by using the reciprocating tribotests, which are close to the actual conditions. The wear surface morphologies and elements distribution were analyzed to explore the wear behaviors and the associated mechanisms of friction pairs under the lubrication incorporated with the ND composites. The results show that the ND additive is beneficial for the pair of Cr liner and CrN-coated piston ring in the friction and wear as well as scuffing properties, and the best concentration of ND additive is expected to be around 1 wt%. But for the BP liner, the developed nanocomposite has a negative impact. The friction force and the wear loss of the pair lubricated by the ND composite-added oil are even worse than that tested with the base lubricating oil.