sc7b01258_si_001.pdf (2.73 MB)
Methionine as a Friction Modifier for Tungsten Carbide-Functionalized Surfaces via in Situ Tribo-Chemical Reactions
journal contribution
posted on 2017-06-20, 00:00 authored by Manel Rodríguez
Ripoll, Vladimir Totolin, Pedro O. Bedolla, Ichiro MinamiThis
work presents a novel method for generating in situ low friction
tribofilms in lubricated contacts using α-amino acid l-methionine as an additive. Methionine is an environmentally acceptable
natural organosulphur compound that is commonly used in the food industry.
Our approach relies in the use of steel surfaces functionalized with
tungsten carbide particles that are tailored to interact with methionine
via a tribo-chemical reaction. The results show that after an induction
period, the friction drops dramatically by 60% down to values of 0.06
when methionine was used as an additive in lubricated tungsten carbide-functionalized
surfaces. The low friction could only be achieved by the coexistence
of tungsten from the functionalized surfaces and sulfur from methionine,
which led to the presence of tribo-chemically generated tribofilms.
Ab initio simulations indicate that the tribo-chemical reaction for
forming tungsten disulfide is energetically favorable, thus attributing
the observed friction reduction mechanism to the in situ formation
of this compound during the sliding process. The concept of functionalizing
surfaces to react with specific additives opens up a wide range of
possibilities, which allows tuning surfaces to target specific additive
interactions. This synergy can be exploited for using novel green
additive technology, thus allowing more environmentally friendly formulations
with outstanding tribological performance.