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Growth of solid tribofilms between moving parts substantially reduces friction and wear, and this is true especially for boundary-lubricated sliding contacts. However, efficacy of the tribofilms relies upon antiwear additives in formulated oil, typically zinc dialkyldithiophosphate, that usually gives rise to adverse environmental impacts. It is desirable to reduce the use of environmentally harmful additives by designing materials of moving parts so that they function properly with base oil lubrication. Herein, CoAl layered double hydroxide (LDH) nanoplatelets were synthesized via a one-step hydrothermal approach. When being lubricated with polyalphaolefin base oil (PAO 4), epoxy nanocomposites reinforced with low-loading LDH exhibit excellent tribological performance. In comparison to neat epoxy, wear of the nanocomposite is reduced by an order of magnitude and friction is decreased by 32%. Our work provides direct evidence that LDH released onto a friction interface facilitates tribofilm growth compensating for lubrication insufficiency of the oil film. This work paves a route for minimizing the dependency on harmful antiwear additives by optimizing tribomaterials.
Yu et al. (Tue,) studied this question.