Experimental investigation on the thermo-physical properties and tribological performance of acidic functionalized graphene dispersed VG-68 hydraulic oil-based nanolubricant

The present work investigates the thermo-physical and tribological properties of acidic functionalized graphene dispersed viscosity grade-68 (VG-68) hydraulic oil nanolubricant and their potential of reducing friction in a mechanical system. The prepared nanolubricant possesses a zeta potential value of-48 mV at pH 7 which shows its high dispersion stability. The thermal conductivity and viscosity index of the nanolubricant enhances with an increase in nanoparticle concentration. A maximum of 67.4 % enhancement in thermal conductivity was observed for 0.4 wt% nanolubricant compared to the base lubricating oil. The viscosity index of 0.4 wt% nanolubricant was enhanced about 2.2 times of the base lubricant. The tribological properties of the nano -lubricants were measured using a rotating disc tribometer with an attachment to measure the coefficient of friction. The nanolubricant (0.4 wt%) reduces the frictional coefficient by a maximum of 21.8 % compared to pure hydraulic oil. The wear rate of the rotating disc also decreases with an increase in the nanoparticle con-centration in hydraulic oil. A maximum decrease of 35.51 % in wear rate was observed by using 0.4 wt% nanolubricant compared to pure hydraulic oil. The acidic functionalized graphene nanoparticles were identified as a potential additive to protect surfaces against wear by reducing the frictional coefficient and enhancing the load-carrying capability of the lubricant.

Automated summary

This study investigates the thermo-physical and tribological properties of acidic functionalized graphene dispersed viscosity grade-68 (VG-68) hydraulic oil nanolubricant and its potential for reducing friction in a mechanical system. The nanolubricant shows high dispersion stability with a zeta potential value of -48 mV at pH 7. The thermal conductivity and viscosity index of the nanolubricant increase with an increase in nanoparticle concentration. The nanolubricant (0.4 wt%) reduces the frictional coefficient by a maximum of 21.8% compared to pure hydraulic oil and decreases the wear rate by a maximum of 35.51%.