Tribological Performance and Lubrication Mechanism of Alumina Nanoparticle Water-Based Suspensions in Ball-on-Three-Plate Testing

The lubrication performance of alumina (Al 2 O 3 ) nanoparticle water-based suspensions was systematically investigated using a ball-on-three-plate testing configuration with alloy steel on stainless steel contact. The size and concentration of Al 2 O 3 nanoparticle were varied to obtain optimal performance. The effects of testing load, sliding speed and contact surface roughness on the lubrication performance of the Al 2 O 3 suspensions were investigated. It was found that 1 to 2 wt.% 30 nm Al 2 O 3 nanoparticle suspensions showed up to 27% friction and 22% wear reduction, in comparison with water glycerol solution. Under different testing conditions, the suspensions also showed noticeably more stable and improved tribological performance. Wear mark analysis revealed that during tribological testing the nanoparticles formed a layer of dynamically balanced tribo-thin film, preventing the direct contact between asperities of alloy steel ball and stainless steel plate. The nanoparticles were also believed to fill up the trenches of the plate surface through mending effect and carry the wear debris induced in running-in period to avoid abrasive wear.