TRIBOLOGICAL PERFORMANCE AND ACTION MECHENISM OF CADMIUM DIALKYLDITHIOPHOSPHATE

摘要

Previous studies have suggested that soft metal compounds, such as copper, tin can produce elemental metal atoms under tribochemical conditions, which deposit on the rubbing surfaces, and play a key role on enhance lubrication and antiwear resistance. Moreover, organic metal compounds containing phosphorus and sulphur groups are effective extreme pressure and antiwear additives. The oil-soluble cadmium dipropyloctyldithiophosphate additive was synthesized. A four-ball tester was used to evaluate the antiwear performance of the additive compared with commercial additive like zinc dithiophosphate in a mineral oil. The results show that it exhibits excellent antiwear and load-carrying capacities. The surface analytical tools such as scanning electron microscopy (SEM) with erergy dispersive X-ray (EDX), X-ray photoelectron spectrometer (XPS) were used to investigate the topography, the compositions contents, and chemical states of some typical elements on the rubbing surface. The surface analyses indicated that tribochemical mixed protective films consists of atomic cadmium, sulphides, sulphates and phosphates were formed on the rubbing surface, which contribute to improve the tribological properties of lubricant. Finally, tribological performance and antiwear mechanism of the additive were discussed, and formation scheme of atomic cadmium was proposed.