Novel Tribological Behavior of Hybrid MWCNTs/MLNGPs as an Additive on Lithium Grease

The goal of this paper is to investigate tribological characteristics of nanographene platelets and hybridized nanocomposite of multiwalled carbon nanotubes (MWCNTs)/multilayer nanographene platelets (MLNGPs)/lithium based-grease. Characterization is done through high resolution transmission electron microscopy (TEM) and X-ray diffraction. While grease properties were tested using Falex four-ball testing machine. Scanning electron microscopy (SEM) and energy dispersive X-ray diffraction (EDX) were utilized to characterize the lubrication mechanism and the worn surface. The results showed that 1% of MLNGPs is the optimum concentration. Wear scar diameter (WSD) was reduced by 66%, friction coefficient was reduced by 91%, while maximum nonseizer load was increased by 90 kg over ordinary lithium grease. Hybrid MWCNTs were studied, and the optimum ratio of MLNGPs to MWCNTs was found to be 4:1.