Tribological Enhancement Features of Various Nanoparticles as Engine Lubricant Additives: An Experimental Study

摘要

This study presents tribological enhancement properties of 40–80 nm copper (Ⅱ) oxide (CuO, nanopowder, ～50 nm, 99.9%trace metal basis), copper iron oxide ( CuFe_2O_4, nanopowder < 100 nm, 98.5% trace metal basis), and copper zinc iron oxide( CuZnFe_2O_4, nanopowder < 100 nm, 99.5% trace metal basis) nanoparticles incorporated (0.1 wt%) in SAE 5W-40 enginelubricant (base oil). Friction and wear evaluations were performed on the sample discs (62–65 HRC, 100 Cr6 steel) usingpin-on-disc tribotester. The samples were immersed in the base oil and the nano-oil (oil with each nanoparticle) ambientsone after another. Stribeck parameter was analyzed to determine the effects of oil bath temperature and pin-sliding speed onfriction and wear within different lubrication regimes. Due to excess increment in an average coefficient of friction (ACOF)above the nanoparticle concentration of 0.1 wt%, the aforementioned amount was used for all experiments. The physicalstructure of the nanoparticles was examined via scanning electron microscopy and atomic force microscopy analyseswere conducted to observe the topography of the worn surfaces. Thermogravimetry (TG)–differential scanning calorimetrymeasurements were also carried out in order to determine the nanoparticle accumulation on the worn surfaces (thermalstability) and to have an idea about probable surface chemical decomposition. A maximum reduction of 50.8% in ACOFwas observed for 5W-40 + CuZnFe_2O_4 suspension under the temperature of 40 ℃ and sliding speed of 1 m/s. Furthermore,minimum surface roughness was also determined for the sample processed in 5W-40 + CuZnFe_2O_4 under the temperatureof 70 ℃ and sliding speed of 0.5 m/s.