Tribolayer formation during macro- and microscale cyclic contact

The formation of tribological surface layers is essential for ultra-mild wear. These surface layers form during machine operation in lubricated conditions with additives. Zinc-dialkyldithiophosphates (ZDDP) are frequently used anti-wear additives, but their future use is limited due to environmental concerns. The design of next generation additives requires a thorough understanding of the tribolayer formation mechanisms of current additives. The present work describes novel macro- and microscale experiments at room temperature that have a limited number of parameters and that use cyclic contact to form tribological surface layers. The new setup allows focusing on the influence of the mechanical stresses, which are very localized in this setup. This study shows that compression creates surface layers even with limited shear driven lubricant flow.