Synthesis and tribological assessment of oil-based nanolubricants blended with nano-zeolite for steel–steel contact

Abstract

This study aims to synthesize zeolite with nano-sized morphology and investigate the tribological performance of nano-zeolite as a lubricating additive dispersed in an oil-based lubricant. Tribological tests were performed and morphologies of wear tracks were characterized to investigate the friction reduction and anti-wear properties of zeolite, respectively. The lubrication mechanism was discussed by illustrating the effects of concentration and particle size on the tribological behavior of zeolite. The optimal concentration of nano-zeolite to improve the tribological performance of the base oil was 2 wt.%, which exhibited a friction reduction of 34.3%. Zeolite particles with larger diameters showed better dispersion stability but worse lubrication performance, which could be concluded from the decrease in the friction reduction ratio. Moreover, the friction coefficient under the lubrication of zeolite at 200°C was 15.8% lower than that of the pure base oil, demonstrating the thermal stability of zeolite. Notably, the application of zeolite resulted in an increase in wear depth due to the occurrence of the three-body abrasion, while the surface asperities of the counterpart were also smoothed in the meantime. This work demonstrates the potential of nano-zeolite to enhance the tribological performance of oil-based lubricants in industrial applications, which could be attributed to their porous structure, lipophilicity, and chemical–thermal stability.