The lubrication mechanism of cerium dithiomolybdate from room temperature to 600 °C

Ce2(MoO2S2)3·4H2O was synthesized in our laboratory and the lubrication performance of the compound as a solid lubricant was examined using a ball-on-disc tribometer. It is effective in reducing friction of Sialon ceramic/W18Cr4V steel friction pair from room temperature to 600 °C. Thermogravimetric analysis, X-ray diffraction, scanning electron microscopy and X-ray photoelectron spectroscopy were used to exhibit the lubrication mechanism of the compound. As the results indicated, Ce2(MoO2S2)3 · 4H2O experienced tribochemical reaction during sliding process at elevated temperature, with the formation of MoS2, which leads to a decrease in the friction coefficient. During the friction process below 400 °C, the element S bonded with Mo in Ce2(MoO2S2)3 acts to reduce Mo6+ and generate MoS2, while during the sliding process at 500 °C, the element S bonded with Ce acts to reduce Mo+6 and generate MoS2.