Abstract
Ionic liquids (ILs) have recently been developed as a novel class of lubricant anti-wear (AW) additives, but the formation mechanism of their wear protective tribofilms is not yet well understood. Unlike the conventional metal-containing AW additives that self-react to grow a tribofilm, the metal-free ILs require a supplier of metal cations in the tribofilm growth. The two apparent sources of metal cations are the contact surface and the wear debris, and the latter contains important 'historical' interface information but often is overlooked. We correlated the morphological and compositional characteristics of tribofilms and wear debris from an IL-lubricated steel-steel contact. A complete multi-step formation mechanism is proposed for the tribofilm of metal-free AW additives, including direct tribochemical reactions between the metallic contact surface with oxygen to form an oxide interlayer, wear debris generation and breakdown, tribofilm growth via mechanical deposition, chemical deposition, and oxygen diffusion.
| Original language | English |
|---|---|
| Article number | 8426 |
| Journal | Scientific Reports |
| Volume | 7 |
| Issue number | 1 |
| DOIs | |
| State | Published - Dec 1 2017 |
Funding
The authors thank Dr. H. Luo from ORNL for the synthesis of the ionic liquid and Dorothy Coffey for FIB preparation of the TEM lamella. The research was sponsored by the Vehicle Technologies Office, Office of Energy Efficiency and Renewable Energy, U.S. Department of Energy (DOE). Electron microscopy characterization and atom probe tomography and was performed at Oak Ridge National Laboratory's Center for Nanophase Materials Sciences (CNMS), which is a U.S. DOE Office of Science User Facility.
| Funders | Funder number |
|---|---|
| CNMS | |
| Oak Ridge National Laboratory | |
| U.S. Department of Energy | |
| Office of Science | |
| Office of Energy Efficiency and Renewable Energy | |
| Oak Ridge National Laboratory |