Abstract: Cu nanoparticles coated with dialkyl dithiophosphate (Cu-DDP) are synthesized in-situ by redox method. The size and structure of the nanoparticles are characterized by using transmission electronic microscopy (TEM) and electronic diffraction (ED) analysis. The anti-wear and friction-reducing and self-repairing behaviors of Cu-DDP as additive in base lubricating oil are investigated on both four-ball machine and MRH-3 stock-on-ring testing machine. Scanning electronic microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and electronic balance (EB) are used to study the grinding crack topography, elemental composition and chemical valence, and the quality change of the self-repairing Cu film on the stock respectively. The test results show that at a load of 300 N a 4% additive amount of Cu nanoparticles exhibits the best self-repairing performance. The stock mass increases by 0.5 mg after 4-hour testing, and the wear scar diameter and friction coefficient are obviously decreased. The Cu nanoparticles is deposited on the frictional surface to form deposited film during the friction process, which could get synergetic effect with the friction chemical reaction film coated on the surface. As a result, the excellent anti-wear and self-repairing performances are obtained.

Key words: Lubricating oil, Mechanism, Nano-Cu additive, Self-repairing performance