Lubrication Performance and Mechanism of Electrostatically Charged Alcohol Aqueous Solvents with Aluminum–Steel Contact

Alcohol aqueous solvents were prepared by individually adding n-propanol, isopropanol, 1,2-propanediol, and glycerol to deionized water for use as lubricants for the electrostatic minimum quantity lubrication (EMQL) machining of aluminum alloys. The tribological characteristics of those formulated alcohol solvents under EMQL were assessed using a four-ball configuration with an aluminum–steel contact, and their static chemisorption on the aluminum surfaces was investigated. It was found that the negatively charged alcohol lubricants (with charging voltages of −5 kV) resulted in 31% and 15% reductions in the coefficient of friction (COF) and wear scar diameter (WSD), respectively, in comparison with those generated using neutral alcohol lubricants. During the EMQL, static charges could help dissociate the alcohol molecules, generating more negative ions, which accelerated the chemisorption of those alcohol molecules on the aluminum surfaces and thereby yielded a relatively homogeneous-reacted film consisting of more carbon and oxygen. This lubricating film improved the interfacial lubrication, thus producing a better tribological performance for the aluminum alloys. The results achieved from this study will offer a new way to develop high-performance lubrication technologies for machining aluminum alloys.