Boundary Lubrication Behaviour of Graphene-Infused Palm Kernel Oil under High-Pressure Forging Conditions

Abstract This study investigates the tribological performance of palm kernel oil (PKO) enhanced with 0.1 wt% AD-Graphene A+ nanoplatelets for cold forging applications. Three lubricants were evaluated: commercial grease, pure PKO, and PKO reinforced with graphene through experimental forging tests and finite element method (FEM) simulations. Friction behavior, stress distribution, surface wear, and tribofilm characteristics were analyzed using FTIR, SEM, Raman spectroscopy, and 3D profilometry. The addition of graphene significantly improved the friction performance of palm kernel oil (PKO), reducing the coefficient of friction to 0.16 compared with 0.22 for pure PKO. The use of commercial grease further reduced the friction value to 0.10. Graphene-enhanced PKO also decreased the forging force by 8-12% relative to pure PKO and promoted the formation of a more stable boundary film due to enriched polar functional groups. Although PKO exhibited the smoothest surface, the graphene-enhanced sample demonstrated superior tribolayer formation and wear resistance. These findings demonstrate the potential of graphene-enhanced bio-based lubricants as sustainable alternatives for high-load metal forming applications.