A Study on the Tribological Performance of an Organic Cadmium Compound as a Lubricant Additive 2004-01-3049

An oil-soluble cadmium dipropyldithiophosphate additive was synthesized. A four-ball wear tester was used to evaluate the tribological performance of the additive in a mineral oil and lubricant grease under different loads and compared with some commercial additives. The results show that it exhibits excellent antiwear and load-carrying capacities, better than commercial additives. In comparison Scanning electron microscopy (SEM) with Energy dispersive X-ray (EDX), and X-ray photoelectron spectrometer (XPS) were used to investigate the topography, and chemical composition of the rubbing surface. Smooth and light topography of the wear scar confirms that the additive showed good antiwear characteristics. Energy dispersive X-ray and X-ray photoelectron spectrometer analyses reveled 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 and grease. Particularly, the soft cadmium film formed plays an important role in improving antiwear properties of oils. Finally, tribological performance and antiwear mechanism of the additive were discussed, and formation scheme for atomic cadmium was proposed.