Abstract
We studied the tribological properties of amorphous molybdenum sulfide (MoSx) thin-film coatings during sliding friction in an oxidizing environment at a low temperature (−100 °C). To obtain films with different sulfur contents (x ~ 2, 3, and 4), we used reactive pulsed laser deposition, where laser ablation of the Mo target was performed in H2S at various pressures. The lowest coefficient of friction (0.08) was observed during tribo-testing of the MoS3 coating. This coating had good ductility and low wear; the wear of a steel counterbody was minimal. The MoS2 coating had the best wear resistance, due to the tribo-film adhering well to the coating in the wear track. Tribo-modification of the MoS2 coating, however, caused a higher coefficient of friction (0.16) and the most intensive wear of the counterbody. The MoS4 coating had inferior tribological properties. This study explored the mechanisms of possible tribo-chemical changes and structural rearrangements in MoSx 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 MoSx films.
Highlights
IntroductionFriction-related reductions in energy consumption in friction joints and the prevention of component wear in these joints under adverse conditions (e.g., low temperatures, aggressive/oxidizing atmosphere) are important research problems in space engineering, cryogenics, micromechanics, and other fields [1,2,3,4]
Friction-related reductions in energy consumption in friction joints and the prevention of component wear in these joints under adverse conditions are important research problems in space engineering, cryogenics, micromechanics, and other fields [1,2,3,4]
We studied the tribological properties of amorphous molybdenum sulfide (MoSx) thin-film coatings during sliding friction in an oxidizing environment at a low temperature (−100 ◦C)
Summary
Friction-related reductions in energy consumption in friction joints and the prevention of component wear in these joints under adverse conditions (e.g., low temperatures, aggressive/oxidizing atmosphere) are important research problems in space engineering, cryogenics, micromechanics, and other fields [1,2,3,4]. These problems are solved by using organic/liquid lubricants or by applying solid lubricant coatings if liquid lubricants cannot be used. The tribological properties of MoS2-based solid lubricant coatings and other transition metal dichalcogenides have been extensively studied over the past 30 years. The structural and chemical state properties of these coatings have been achieved through pulsed laser deposition (PLD) [15,16,17] and liquid-based electrodeposition [18]
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