Lubrication mechanism of cadmium tetrathiomolybdate

A potential high temperature lubricant cadmium tetrathiomolybdate (CdMoS₄) was prepared. Thermal gravimetric analysis (TGA) was used to examine its thermal stability, and a high temperature ball-on-disc friction and wear tester was used to evaluate its lubricity for a Sialon ceramic/W18Cr4V steel pair from room temperature to 500°C. The worn surface of the W18Cr4V steel disc was analyzed with X-ray photoelectron spectroscopy (XPS) and X-ray diffraction. The results show that CdMoS₄ has good lubricity from room temperature to 400°C, and the friction coefficient increases slowly with the increase of temperature. CdMoS₄ experiences tribochemical reaction during friction process, and the high valence Mo was deoxidized by S with the formation of MoS₂, so the friction coefficient decreases.