Influence of nanometer lanthanum fluoride on friction and wear behaviors of bonded molybdenum disulfide solid lubricating films

Influence of nanometer lanthanum fluoride (nano-LaF3) on the friction and wear behavior of bonded molybdenum disulfide (MoS2) solid lubricating film was investigated using an oscillating friction-wear tester under dry friction condition. The worn surface of the lubricating film and the transfer film formed on the surface of the counterpart ball were observed by SEM. The microstructure of the lubricating film filled with nano-LaF3 and the distribution of F and La in the lubricating film were investigated with transmission electron microscopy (TEM) and field emission scanning electron microscope (FESEM) equipped with an energy dispersive X-ray spectrometer, respectively. It was found that nano-LaF3 as a filler contributes to improve the wear-resistance property of the lubricating film. The lubricating film modified with nano-LaF3 filler exhibits better wear-resistance property than that of the lubricating film without nano-LaF3 filler at a relatively lower load (less than 250 N) and within a wide oscillatory frequency range between 5 and 35 Hz. However, the incorporation of nano-LaF3 filler results in small increase of friction coefficient of the lubricating film. Transmission electron microscopy (TEM) and elementally X-ray map results of the lubricating film modified with nano-LaF3 filler indicate that partial LaF3 nanoparticles distribute around the MoS2 particles, while other LaF3 nanoparticles disperse in the binder. The SEM morphology of the frictional surface shows that the filler of nano-LaF3 is able to enhance the compactness of the frictional surface, and results in an improvement of the wear-resistance property of the MoS2 lubricating film.