Synergistic anti-friction performance and lubricating film mechanism of erucamide and <i>N</i> -phenyl-α-naphthylamine in polyurea grease at elevated temperatures

The synergistic effect of anti-wear and antioxidant additives in lubricating grease can effectively reduce friction and wear. In this study, a polyurea grease containing 2 wt% erucamide (ER) and 1 wt% <i>N</i>-phenyl-α-naphthylamine (<i>N</i>-PAN) was prepared, and its tribological performance on GCr15 steel at different temperatures was systematically investigated. The results show that the average friction coefficient of the grease with ER and <i>N</i>-PAN decreases by approximately 32% compared with the base polyurea grease, exhibiting the best tribological performance at 75 °C (average friction coefficient = 0.088). Surface characterization reveals that the synergistic action of ER and <i>N</i>-PAN promotes the formation of a dense and durable lubricating film. ER molecules form a bilayer structure, filling the voids of the base oil and transforming sliding friction into rolling friction, while <i>N</i>-PAN effectively inhibits oxidation and retards film degradation. This synergistic mechanism significantly enhances the high-temperature friction-reducing and antioxidative properties of the grease, demonstrating its potential for high-temperature mechanical lubrication applications.