Investigation of the thermal stability and lubricity of zinc tetrathiomolybdenate

Zinc tetrathiomolybdenate (ZnMoS₄) was prepared. Thermal gravimetric analysis was used to examine its thermal stability, while a ball-on-disc tester was used to evaluate its lubricity for a Sialon ceramic/W18Cr4V steel pair at 500°C. ZnMoS₄ begins to decompose at 236°C in air, with the formation of ZnMoS₃S, and the final oxidized product of ZnMoS₄ is generated at 711°C in air. ZnMoS₄ begins to decompose at about 362°C in N₂ wit the formation of ZnMoS₂, accompanied by the generation of ZnMoS at 507°C. ZnMoS₄ has good lubricity from room temperature to 500°C, and the friction coefficient rises slowly with the increase of temperature. ZnMoS₂ experienced oxidation during friction process, with the formation of ZnMoO₄ and ZnSO₄.