The tribological behaviour of ZnO nanoparticles as an additive to PAO6

This is a study on the tribological behaviour of ZnO nanoparticles as an additive to a polyalphaolefin (PAO6) and on the influence of dispersing agents (OL100 and OL300). Anti-wear tests were run on a Falex Roxana four-ball machine and EP properties were obtained using a Stanhope Seta Shell Four-Ball EP Lubricant Tester. Ensuing SEM and EDS analysis of the worn surface highlighted a number of conclusions: OL300 has better dispersant properties than OL100; OL100 and OL300 are potentially useful as wear reducer additives in PAO6; formation of aggregates was found for 1 and 1.5% of ZnO in PAO6 + 3% OL300 suspension, and these non-coated ZnO nanoparticles had an abrasive behaviour in the AW region, despite their lower hardness compared to steel surfaces; ZnO nanoparticles do not act as anti-wear agent under certain conditions but in EP conditions, from the initial seizure load, they decrease wear; the EP behaviour improvement of PAO6 + 1% OL300 + ZnO mixtures was related to the increase of ZnO nanoparticle concentration and their surface deposition on the wear scar surface; PAO6 + 3% OL300 + 0.3% ZnO displayed the best EP behaviour in PAO6 + 3% OL300 + ZnO mixtures, while PAO6 + 3% OL300 + 1% ZnO and PAO6 + 3% OL300 + 3% ZnO were worse, despite Zn deposition on the wear scar surface.