Nanoparticles of Zn and ZnO as extreme pressure (EP) additives for lubricants

The tribological behavior of moving components and tooling in the automotive industry is a critical issue for improving tool life and increasing efficiency. This work discusses the effects of Zn and ZnO nanoparticle additives homogeneously dispersed within a metal-forming synthetic fluid at various filler fractions: 0.01, 0.05 and 0.10wt.%. Nanolubricants were evaluated under scuffing conditions at extreme pressures (EP) conditions using a four-ball tribotester in order to obtain the load-carrying capacity (pοz) behavior, and overall tribological characteristics. This method has shown, with great precision, the influence of the nanofillers on the EP behavior of conventional lubricants. Worn surfaces were characterized through Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS) to determine the tribological mechanisms of nanoparticles. An Alicona 3D surface measuring system was used for measuring the surface roughness of the wear scars. Both nanoparticles exhibited better friction-reducing and anti-wear properties compared to the base synthetic fluid. For Zn-based nanolubricants, an enhancement of ~180% in ροz was obtained with 0.10wt.%, showing the effect of the spherical nanostructures that were tribosintered onto the surface due to the EPs of the test. Furthermore, the highest enhancement in pοz (up to 250%) was achieved with incorporation of 0.10wt.% of ZnO demonstrating the potential of nanolubricants for improving the efficiency of mechanical components.