Tribological performance of hBN-enhanced palm kernel oil nanolubricants for hydrogen engine applications

The shift toward hydrogen internal combustion engines (H 2 -ICE) as a clean energy solution demands high-performance, eco-friendly lubricants compatible with new combustion environments. This study evaluates the dispersion stability, kinematic viscosity, and tribological performance of palm kernel oil (PKO)-based lubricants enhanced with hexagonal boron nitride (hBN) nanoparticles, targeting their suitability for H 2 -ICE applications. Six nanolubricant formulations (0–1.0 wt% hBN) were tested using a four-ball tribotester (ASTM D4172). Results revealed that a 0.05 wt% hBN concentration yielded optimal performance, reducing the coefficient of friction (COF) from 0.089 to 0.073 (18.1% reduction) and the wear scar diameter (WSD) from 550 µm to 485 µm (11.9% reduction) compared to the base PKO lubricant. The findings highlight the critical role of nanoparticle concentration in preventing agglomeration and achieving stable dispersion, directly influencing lubrication effectiveness. The enhanced tribological behavior and biodegradability of the optimized PKO-based nanolubricant make it a promising candidate for sustainable lubrication in hydrogen-fueled engines.