Effect of PAO base oils with different viscosities on rheological and tribological properties of lithium greases

Greases synthesized with high-viscosity PAO exhibited superior tribological performance (exhibiting average friction coefficients of 0.072 and 0.062, respectively), representing reductions of 37% and 24% compared to their respective base oils. Wear volumes were concurrently reduced by 29% and 19%. Under elastohydrodynamic lubrication (EHL) conditions, the film thickness of low-viscosity PAO greases was predominantly governed by residual thickener fiber clusters within the contact zone.

High-viscosity PAO greases maintained a higher film thickness, relying on a dimpled oil film formed by squeeze action. Owing to their higher porosity and larger pore size, low-viscosity PAO greases demonstrated a higher oil bleeding rate. This facilitated rapid replenishment of the lubricant reservoir within the contact zone, ultimately resulting in a larger recovered reservoir size.

This research provides a robust theoretical foundation and technical guidance for the selection of PAO base oils in lubricating grease formulation and application.