Synergistic effects of graphene additives and piston ring surface treatment on friction properties of engine oil

Abstract

The use of nano-additives improves the performance of lubricants by minimizing energy loss due to friction and wear. In this study, tribological properties of cylinder liner-piston ring were improved by modifying monolayer graphene with surfactants. Additionally, surface chemical chromium coating and chemical heat treatment were conducted on the friction surfaces of specially made piston ring samples to further enhance the friction of piston ring. From the comparison of experimental results, the best lubrication performance was exhibited by the use of 0.05 wt% modified graphene nano-lubricant, which reduced the friction coefficient by approximately 31.1% and improved the anti-wear performance by approximately 59.6% compared to the base oil. In addition, the effect of the graphene nano-lubricant on the friction performance of chromium-coated samples was more substantial than that of the chemically heat-treated samples. Under high-temperature and heavy-load conditions, the corresponding friction coefficient was reduced by 15.5% and 34%, respectively, when compared to the base oils. This can be attributed to the porous surface of the chromium-coated sample, which promotes the storage of the graphene nano-lubricant. The results highlight the synergistic effect of graphene additives and piston ring surface treatment on the tribological performance.