Tribological and rheological properties of calcium grease with hybrid nano additives

Abstract

Nanocomposite grease was created to reduce wear and friction on surfaces and enhance thermal conductivity. The tribological and rheological properties of nano grease were studied. Calcium grease with varied doses of hybrid TiO₂/CNTs/GNs (0.5, 1, 2, 3 wt.%) was prepared. Transmission electron microscope (TEM) was applied to look at the microstructure of nano grease. Tribological and rheological properties of the nano grease were examined by using a four-ball tester. Wear scar diameter (WSD) was reduced by 30% at the optimal TiO₂/CNTs/GNs concentration of 2% before beginning to rise. As TiO₂/CNTs/GNs are applied in concentrations ranging from 0 to 2 wt.%, the friction coefficient of nano additive containing calcium grease steadily declines. At 2% concentration, the reduction in coefficient of friction was 45% about base grease. The friction coefficient was increased after that to 3 wt.%. Shear rate was reduced when the dose of TiO₂/CNTs/GNs was increased. As the concentration of nanomaterials and shear rate increased, so did the viscosity of nano grease. Shear stress and apparent viscosity of the calcium grease containing 3% by weight of TiO₂/CNTs/GNs are 43% higher than pure calcium grease, although they are still much lower than pure grease. The inclusion of the nanomaterial causes a roughly 19.5% increase in the dropping point of base grease. The thermal conductivity of nano grease is significantly improved by nano additives, increasing by around 130%, and the additives have a dramatic linear growth on the thermal conductivity of nano grease.

Graphical Abstract

Keywords:

• Calcium grease
• nano additive
• tribology
• rheology
• shear stress