Graphite Lubrication for Rolling Bearings: A Multiscale Analysis

This work demonstrates the potential of graphite as a solid lubricant for rolling bearings, distinguishing it from its more common use as an additive in oils and greases. A complete multiscale overview of the tribological behavior of air-sprayed graphite ranging from technical components to the atomic scale is provided. Rolling bearing tests confirm the efficacy of graphite in reducing friction and wear, driven by the formation of a tribofilm. These findings are validated by mini traction machine (MTM) measurements, while microtribometer experiments highlight the dependency of lubrication performance on coating thickness and applied loads. Furthermore, it is demonstrated that the tribofilm undergoes a complex multistage evolution until its failure. Humidity-controlled experiments demonstrate the significant influence of environmental conditions on tribofilm formation and wear behavior. These findings are validated by quantum chemical simulations. Our findings provide insights into the tribological mechanisms of graphite coatings and offer a foundation for their future application in industrial settings.