Comparative Study on the Tribological Performances of Barium Perrhenate, Molybdenum Disulfide, and Calcium Carbonate as Lubricant Additives in a Wide Temperature Range

摘要

Barium perrhenate [Ba(ReO4)(2)], a compound used as an oil additive, was synthesized via the aqua-solution method. Its tribological properties were examined using the four-ball test and ball-on-disc tribotester in a wide temperature range and compared with those of oil that contained the additive molybdenum disulfide (MoS2) and calcium carbonate (CaCO3) compound. X-ray diffraction analysis, scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and differential thermal analysis/thermogravimetry were performed to determine the possible mechanism of the antifriction behavior of the lubricants. Results of the four-ball test showed that all of the additives can improve the extreme pressure property of the base oil and decrease the wear scar diameters of low-carbon steel balls. The results of the ball-on-disc test suggested that the MoS2 additive exhibited better lubrication property than the Ba(ReO4)(2) and CaCO3 additives at below 450 degrees C. The CaCO3 additive displayed moderate performance in friction reducing in the high-temperature period. The Ba(ReO4)(2) additive exhibited preferable comprehensive antifriction performance in a wide temperature range because of its intrinsic shear-susceptible property and crystalline change with varied temperatures, which could form a protective layer with some native oxides of the disc sample and thus effectively prevented direct contact between rubbing parts. The detailed friction-reducing mechanism of the three additives is also discussed.