Effects of solid lubricant MoS2 on the tribological behavior of hot-pressed Ni/MoS2 self-lubricating composites at elevated temperatures

Various MoS2 compositions of hot-pressed, sintered Ni/MoS2 composites were made and tested in a ball-on-disk wear test machine. The friction and wear of the composites with reciprocating sliding were measured at elevated temperatures, as well as at room temperature. Stepwise loading test results at room temperature and 25 percent relative humidity showed that as the MoS2 content increased the friction and wear of the composite decreased up to 60 wt% MoS2 and then increased. However, at elevated temperatures, the friction and wear properties of the composite with 80 wt% MoS2 were better than that with 60 wt% MoS2 The worn surfaces of the composites have been analyzed by electron microscopy techniques. Scanning electron microscope analysis showed that friction and wear are related to the formation of solid films formed on the sliding surfaces. The more cohesive the films, the lower the friction and wear, and this can be used as a criterion of the tribological behavior of the composite. Transmission electron microscopy showed that the MoS2 films formed on both sliding surfacer have their basal planes (0001) parallel to the surfaces. This film texture is beneficial to a reduction of the friction and wear.