The Size Effect of Boron Nitride Particles on the Tribological Performance of Biolubricants for Energy Conservation and Sustainability

The size of particulate additives in a bio-based lubricant influences their friction and wear performance during sliding contact. The present investigation evaluates the effect of boron nitride particle size on the tribological performance of canola oil-based lubricant mixtures. During sliding experiments, micron-, submicron-, and nanometer-sized boron nitride particle additives were considered. Friction and wear measurements were carried out on the prepared lubricant mixtures using a pin-on-disk tribometer at ambient conditions. A scanning electron microscope and optical profilometer were used for topographical studies to evaluate the influence of particle size on wear damage and surface roughness. The results revealed that the nanometer-sized particulate mixture outperformed micron- and submicron-sized particulate combinations in terms of friction and wear performance and provided a 90 % smoother surface finish. Furthermore, the tribological response of canola oil containing micron- or submicron-sized particles was found to be significantly enhanced by the addition of nano-sized particles, where the friction and wear were reduced by 40 and 70 %, respectively. It was inferred that the nano-sized particles were able to better coalesce in the asperity valleys due to their small size and spherical shape, which provided them with enhanced tribological properties in comparison with the micron- and submicron-sized particles that were larger and exhibited a plate-shaped in geometry. Newly developed non-dimensional surface roughness parameters were introduced to quantify the influence of particle size and the mechanisms involved in the tribological phenomena. The state of lubricants derived from bio-based feedstock were subsequently explored for their influence on energy conservation and sustainability, as well as their potential impact on the lubricant market place.