Friction and wear mechanisms of castor oil with addition of hexagonal boron nitride nanoparticles

The friction properties of castor oil with the addition of hBN nanoparticles (nanofluid for short) and its wear resistance enhancement mechanism are investigated regarding the oil film thickness and lubrication regime resulting from changes in the viscosity of the nanofluid. The nanofluid with 5 wt% hBN additive leads to a 21.74% increase in the friction coefficient but a 55.05% improvement in the wear quantity at low load and high speed because of higher viscosity and larger oil film thickness. At a high load and low speed, the friction regimes turn into boundary lubrication owing to lower viscosity; a 30.2% decrease in the friction coefficient and a 51.74% improvement in the wear quantity for nanofluid with 1 wt% hBN additive are achieved.