| AVS 62nd International Symposium & Exhibition | |
| Tribology Focus Topic | Thursday Sessions |
| Session TR+TF-ThM |
| Session: | Nanolubricants and Coatings |
| Presenter: | Clotilde Minfray, Ecole Centrale de Lyon - LTDS, France |
| Authors: | C. Minfray, Ecole Centrale de Lyon - LTDS, France M. De Feo, Ecole Centrale de Lyon - LTDS, France M.I. De Barros Bouchet, Ecole Centrale de Lyon - LTDS, France B. Thiebaut, Solaize Research Center, France T. Le Mogne, Ecole Centrale de Lyon - LTDS, France B. Vacher, Ecole Centrale de Lyon - LTDS, France J.M. Martin, Ecole Centrale de Lyon - LTDS, France |
| Correspondent: | Click to Email |
Nowadays, MoDTC is one of the best-known friction modifier additives used in engine oils for its friction reduction properties. A vast number of papers tackle the subject and converge on the fact that the generation of MoS2 flake in the contact (in tribofilm) is at the origin of the friction reduction. But it is also known that this positive friction reduction effect is not so durable in time. Therefore, the investigation of MoDTC chemical degradation mechanism and its impact on the tribological properties in steel/steel contacts is of great interest.
It is proposed here to age a lubricant made of mineral base oil blended with 1%w of MoDTC with a thermo-oxidative procedure (open air - 160°C) for different durations. The aged lubricants are then tested under boundary lubrication conditions, with ball-on-flat reciprocating tests running at 100°C. Balls and flats are both in AISI52100 steel.
Concerning the results, clear differences are found in terms of friction behavior as a function of ageing time. A relation between ageing and induction time needed to reach the “low” friction regime is also established. Tribofilms generated on flats were then analyzed by means of XPS surface analysis and FIB-TEM observations for a precise chemical and morphological characterization of each flat sample. The possible presence of two types of molybdenum oxi-sulfide compounds, more or less oxidized, is suggested by XPS results and discussed regarding the friction behavior. Moreover, the TEM observations carried out suggest tribofilms differences in terms of morphology, size and organization. Finally, the effect of MoDTC ageing on friction behavior is discussed considering the composition of tribofilms but also taking into account MoDTC depletion in the bulk of the lubricant, thanks to High Performance Liquid Chromatography (HPLC) experiments.