Tribological Properties of ZnS(NH2CH2CH2NH2)0.5 and ZnS as Additives in Lithium Grease

The layered compound ZnS(NH2CH2CH2NH2)0.5 was evaluated as an additive in grease with different concentrations by using a four-ball tribometer. Results show that ZnS(NH2CH2CH2NH2)0.5 grease has good load bearing ability and excellent anti-wear properties. ZnS(NH2CH2CH2NH2)0.5 revealed better wear resistance than that of ZnS under all test conditions. The reason for this may be that the two-dimensional structure of ZnS(NH2CH2CH2NH2)0.5, with larger interspaces, facilitates an easier sliding process, improving the anti-wear performance. The mechanism was estimated through analysis of the worn surface with SEM, EDS, 3D, and XPS. XPS analysis results show that the tribofilm was mainly composed of FeS, ZnS, ZnO, FexOy, Feu(SO4)v, and ZnSO4. Owing to the simple synthetic method and superior tribological properties as a grease-based additive, ZnS(NH2CH2CH2NH2)0.5 holds great potential for use in demanding industrial applications in the future.