Ionic liquid stabilized nanoparticle additive in a steel-ceramic contact for extreme pressure application

This study presents and discusses the friction, wear and extreme pressure behavior of nanoparticles suspended in a gear base oil. Zero, 0.5, 1 and 2 %wt diamond and Zinc Oxide (ZnO) nanoparticles were separately dispersed in base stock and stabilized using a phosphonium ionic liquid. A rotary alumina ceramic ball on 20MnCr5 gear steel disc configuration was used to quantify the tribological performance of the formulated nanofluids. The results showed that the ionic liquid stabilizer in the base stock bonded to the surface of the disk resulted in the best anti-friction behavior but was accompanied by increased wear. The unique structure of diamond nanoparticles produced the best anti-wear behavior. Both diamond and ZnO nanoparticles stabilized with ionic liquid were effective in preventing scuffing. Thus, the nanoparticles have potential to be extreme pressure additives for gear oil applications. All concentrations of diamond nanoparticles and ZnO nanoparticles resulted in smoother surfaces after testing due to the nanoparticles acting as three body wear polishing agents.