Preparation and high temperature tribological properties of core-shell MoS₂@SiO₂ nanocomposites

Molybdenum disulfide (MoS₂) is easy to be oxidized when used at high temperature, which leads to significant deterioration of its tribological properties, showing a high friction coefficient. In order to improve the tribological properties of MoS₂ lubricant under high temperature environment, core-shell MoS₂@SiO₂ nanocomposites was formed by hydrothermal method and improved Stöber method. The morphology, size and composition of the nano materials were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM) and X-ray diffraction (XRD). The micro results show that the core-shell structure composite is successfully prepared, with an average particle size of 250 nm. The high temperature friction test of prepared MoS₂@SiO₂ solid lubrication coating was carried out, and the MoS₂ coating was used as a comparison. The morphology and structure of the coating were characterized by SEM and XRD, and the wear rate of the coating was characterized by a 3D profiler. The results show that the friction coefficient of the MoS₂@SiO₂ coating at 680℃ is 0.2 and relatively stable, while MoS₂ coating rapidly fail. The MoS₂@SiO₂ coating had better wear resistance, with a wear rate at 25.86%, lower than that of MoS₂ coating. After the friction tests, MoS₂ still existed in the wear scar area of the MoS₂@SiO₂ coating, which was covered by the lubricating film. However, the substrate in the wear zone of MoS₂ coating was completely exposed. It is thus shown that the encapsulation of the SiO₂ shell retards the rapid oxidation of MoS₂ at high temperatures and the two synergistically lubricate to prolong the service life of the coating.