Student poster abstract: Characterization of nanoscale surface films in solid lubricants

MoS ₂, a lamellar solid lubricant exhibiting extremely low friction in vacuum, is often used to lubricate sliding interfaces. MoS ₂ accommodates motion by forming sliding-induced low shear-strength surface films called tribofllms. The effect of environment on evolution of a stable sliding interface was investigated, including the properties of these films at relevant length-scales, to understand their contributions to macroscale friction and wear. Wear-rate measurements were made on a MoS ₂ coating. The moisture-dependence of MoS ₂ wear across two distinct time-scales was observed, i.e., the immediate environment and the coating exposure history, suggesting effects of storage conditions on prevailing coating wear rate. The sensitivity of MoS ₂ friction to annealing indicated the tendency of MoS ₂ to act as a sink for gradual moisture uptake over time, which during annealing is thermally driven out. Sliding-induced surface structure affected frictional response and moisture sensitivity.