Study On The Tribological Properties Of Micro/nano Lamellar Lubricant Additives

Lamellar nanomaterials are widely used as solid lubricants,such as graphite,molybdenum disulfide and so on.Their common characteristic of the lamellar nanomaterials is the layered structures that within each atomic layer,covalent bonding bonds atoms together,and van der Waals interaction presents between two adjacent layers.In order to verify the tribological properties of this layered nanomaterial as lubricant additive and reveal the friction-reducing and anti-wear mechanism,three different types of layered nanomaterials: MoO₃,ZrS₂ and montmorillonite were selected for friction and wear tests.The test results and surface analysis of the wear scar can be used to provide the experimental basis for the lamellar nanomaterials as lubricant additives.The first chapter mainly introduces the role,classification and future development trend of the existing lubricant additives,summarizes the categories of two-dimensional lamellar materials and their research status as lubricant additives,and introduces the main anti-friction mechanisms.The second chapter used the micro/nano lamellar MoO₃ as the research object.In frictional tests,it was found that the micro/nano MoO₃ lubricant additive can effectively reduce the friction coefficient of base oil,noise and vibration.Because van der Waals force is weak,the adjacent layers are slipped along the direction parallel to the crystal plane by shear force.The friction between the metals is converted into van der Waals force.The optimum friction-reducing concentration of micro/nano MoO₃ is0.5 wt%.The micro/nano lamellar MoO₃ can extend the working temperature of base oil from 100 ? to 150 ?.In wear tests,it was found that the amount of micro/nano MoO₃ could reduce adhesive wear and surface damage.it was also found that micro/nano MoO₃ not only effectively reduced the friction coefficient of the run-in phase,but also reduced the depth and width of the wear scar.The optimum anti-wear concentration of micro/nano MoO₃ is 0.1 wt%.The wear surface was characterized by surface roughness meter,high-power microscope and X-ray energy dispersive spectrometer?EDS?.It was found that the wear surfaces lubricated by base oils with micro/nano MoO₃ were more smooth and the Mo element was detected.It proved that under the action of friction chemistry,MoO₃ participated in the formation of the friction film and filled and repaired the damaged surfaces.By testing the PB value of lubricant oils,it was found that 1.5wt% of micro/nano MoO₃ could improve the extreme pressure performance of base oil.The stribeck curves proved that micro/nanolayered MoO₃ can effectively reduce the friction coefficient of base oil in hydrodynamic lubrication,mixed lubrication and boundary lubrication regimes.The third chapter used the micro/nano lamellar ZrS₂ as the research object.In frictional tests,it was found that the micro/nano ZrS₂ can effectively reduce the friction coefficient of base oil in the run-in period,noise and vibration.The optimum friction-reducing concentration of micro/nano ZrS₂ is 1 wt%.The micro/nano ZrS₂ can extend the working temperature of base oil from 100 ? to 200 ?.In wear tests,it was found that micro/nano ZrS₂ not only effectively reduced the friction coefficient in both the run-in and stable wear periods,but also reduced the attrition.The optimum anti-wear concentration of micro/nano ZrS₂ is 1 wt%.The wear surface was characterized by surface roughness meter,high power microscope and EDS.It was found that the wear scars lubricated by base oils with micro/nano ZrS₂ were more shallow and smooth and the Zr and S elements were detected.It proved that ZrS₂ participated in the formation of the friction film and repaired the damaged surface.The PB value of base oil with 1 wt% of micro/nano ZrS₂ was improved by twelve levels.The stribeck curves proved that micro/nano layered ZrS₂ can reduce the friction coefficient of base oil in hydrodynamic lubrication,mixed lubrication and boundary lubrication regimes.In hydrodynamic lubrication regime,the effect of layered micro/nano MoO₃ was better than lamellar micro/nano ZrS₂ with strip morphology.The forth chapter used the micro/nano lamellar montmorillonite as the research object.In frictional and wear tests,2 wt% 6 wt% of micro/nano montmorillonite in the base oil significantly reduced friction coefficient and wear amount,and 5 wt%was the best concentration.From the 2D profile curves and SEM images,it was found that the depth of the wear scars lubricated by base oils with 2 wt% 6 wt% of micro/nano montmorillonite were greatly reduced,and the surfaces were covered with a thin dark film.From the EDS spectra,Al and Si elements originally existed in montmorillonite were detected,which proved that montmorillonite took part in the formation of the surface film with excellent tribological properties that resist further wear and repair the surface.In the fifth chapter,results of the research on the three micro/nano lamellar materials were summarized,and the future research work was prospected.