Reactive Pulsed Laser Deposition of Clustered-Type MoS ( ~ 2, 3, and 4) Films and Their Solid Lubricant Properties at Low Temperature.

We studied the tribological properties of amorphous molybdenum sulfide (MoS) thin-film coatings during sliding friction in an oxidizing environment at a low temperature (-100 °C). To obtain films with different sulfur contents ( ~ 2, 3, and 4), we used reactive pulsed laser deposition, where laser ablation of the Mo target was performed in HS at various pressures. The lowest coefficient of friction (0.08) was observed during tribo-testing of the MoS coating. This coating had good ductility and low wear; the wear of a steel counterbody was minimal. The MoS coating had the best wear resistance, due to the tribo-film adhering well to the coating in the wear track. Tribo-modification of the MoS coating, however, caused a higher coefficient of friction (0.16) and the most intensive wear of the counterbody. The MoS coating had inferior tribological properties. This study explored the mechanisms of possible tribo-chemical changes and structural rearrangements in MoS coatings upon contact with a counterbody when exposed to oxygen and water. The properties of the tribo-film and the efficiency of its transfer onto the coating and/or the counterbody largely depended on local atomic packing of the nanoclusters that formed the structure of the amorphous MoS films.