Tribological Performance for Steel–Steel Contact Interfaces Using Hybrid MWCNTs/Al₂O₃ Nanoparticles as Oil-Based Additives in Engines

Numerous problems occur during engine operation, such as start-up, lack of lubrication, and overheating, resulting in engine components’ wear, power loss, and fuel consumption. Nanomaterials dispersed in engine oil can play an important role in improving the tribological properties of oil lubricants. This study investigated the influence of multi-walled carbon nanotubes (MWCNTs) and aluminum oxide nanoparticles (Al₂O₃ NPs) as nano-additives for lubricants. Different engine oil samples were loaded with 0.5–2.0 wt% Al₂O₃ NPs and 0.5–1.0 wt% MWCNTs and compared with unmodified oil. The tribological performance of the nano lubricants was investigated using the four-ball test method. In addition, the wear scar in the engine was evaluated using 3D micrographs and scanning electron microscopy (SEM). The results of the sliding surfaces with hybrid MWCNTs/Al₂O₃ NPs showed better friction performance and wear resistance. The coefficient of friction (COF) and wear scar width were improved by 47.9% and 51.5%, respectively, compared with unmodified oil.