Abstract
Although grease can effectively lubricate machines, lubrication failure may occur under high speed and heavy load conditions. In this study, Mn3O4/graphene nanocomposites (Mn3O4#G) were synthetized using a hydrothermal method as lubricant additives. The lubrication properties of compound grease with Mn3O4#G nanocomposite additive under heavy contact loads of 600–900 N (3.95–4.59 GPa) were investigated. First, the nanocomposites were dispersed into L-XBCEA 0 lithium grease via successive electromagnetic stirring, ultrasound vibration, and three-roll milling. Compound grease with additives of commercial graphene (Com#G) was also investigated for comparison. Tribological test results revealed that the trace amounts of Mn3O4#G (as low as 0.02 wt%) could reduce the coefficient of friction (COF) of grease significantly. When the concentration of Mn3O4#G was 0.1 wt%, the COF and wear depth were 43.5% and 86.1%, lower than those of pure graphene, respectively. In addition, under the effect of friction, the microstructure of graphene in Mn3O4#G nanocomposites tends to be ordered and normalized. Furthermore, most of the Mn3O4 transformed into Mn2O3 owing to the high temperature generated from friction. Using the Ar gas cluster ion beam sputtering method, the thickness of the tribofilm was estimated to be 25–34 nm. Finally, the improvement of the lubrication properties was attributed to the synergistic effect of the adsorbed tribofilm, i.e., the graphene island effect and the filling effect of Mn3O4#G.
Highlights
Lubricants are widely used for reducing equipment friction and wear, thereby increasing the service life of machines, especially in heavy contact load conditions [1, 2]
We proposed an in situ green method to synthesize Mn3O4/graphene nanocomposites (Mn3O4#G) by introducing Mn in the synthesis process of Graphene oxide (GO)
It can be seen that Mn3O4#G has the characteristics of “trace but efficient”, and reduces the coefficient of friction (COF) of the compound grease from 0.193 to 0.131 at a concentration as low as 0.02 wt%
Summary
Lubricants are widely used for reducing equipment friction and wear, thereby increasing the service life of machines, especially in heavy contact load conditions [1, 2]. Nehme [8] studied the tribological properties of zinc dialkyl dithiophosphates (ZDDP) with added submicron particles of titanium fluoride or iron fluoride along with polytetrafluoroethylene under heavy load condition (336 N; 2.6 GPa) and different speeds He investigated the wear behavior of MoS2 grease under variable loads and speeds for extreme pressure application with a four-ball wear tester (393–786 N) [9]. Li et al [28] investigated the effect of the exfoliated state of graphene sheets on the lubrication and anti-friction performance His results indicated that graphene with a loose interlayer structure and extremely low particle size can improve the tribological properties of oil effectively. The tribological properties of this additive in grease and the performance of the composite-based grease under high-speed and heavy-load conditions have not been studied. We investigate the lubrication properties of Mn3O4#G as an additive in grease under high speed (80 mm/s) and heavy load (3.95–4.59 GPa). The results of this study will provide useful information to develop an effective way to improve the lubrication performance of commercialgrade grease
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
