Lanthanum dialkyldithiophosphate (LaDDP) was synthesised. The tribological properties of a combination additive of LaDDP and a n organo-borate (OB) i n oil were evaluated with a fourball test machine. The results show that the combination of LaDDP and OB gives better load-carrying capacity and antiwear and friction-reducing properties than the individual components. Rubbed surfaces after the friction tests were investigated using X-ray photoelectron spectroscopy, Auger electron spectroscopy, and microhardness testing. The results indicate that a boundary film is composed of deposit films (including La,O, and B,O,), chemical reaction films (including FeSO,, FePO,, and FeS), and a tribodiffusion layer (including La and B). Lanthanum can promote the decomposirion of OB and the tribodiffusion of boron. From a mass spectroscopy analysis a tribochemical mechanism is suggested.
Carbon nanotubes (CNTs) was introduced into Ni60/Al2O3coating by flame spraying. The effect of adding CNTs on the tribological properties of the coating was studied by varying the CNTs content as 0.0, 1.5, 3.0 and 4.5 wt% in the Ni60/Al2O3powders. The microhardness tester was used to measure the microhardness of the coating. Wear tests were performed on a pin-on-disk tribometer, to evaluate the tribological properties of the Ni60/Al2O3/CNTs coatings. Microstructural characterization was performed using scanning and transmission electron microscopy. Ni60/Al2O3/CNTs coatings revealed a lower wear rate and friction coefficient compared with the original coating, and their wear rates and friction coefficients showed a decreasing trend with increasing mass fraction of CNTs within the range from 0 to 3.0 wt% due to the effects of the reinforcement and reduced friction of CNTs. The results showed that the CNTs played dual roles in improving the tribological performance of the coating, indirectly by influencing the microstructure and mechanical properties of the coating and directly by acting as a lubricating medium.
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