TRIBOLOGICAL PERFORMANCE OF LITHIUM GREASE DISPERSED BY SILCA NANO PARTICLES AND CARBON NANOTUBES

The present study deals to evaluate the effect of mixing lithium grease by paraffin oil that dispersed with silicon dioxide (SiO2) nanoparticles and carbon nanotubes (CNT) on the lubricating properties of deep drawing process. Friction and wear tests were conducted by the reciprocating sliding of bearing steel ball on aluminum (Al) sheet lubricated by the mixture. It was found that friction coefficient displayed by the grease dispersed by CNT/ SiO2 displayed the highest values followed by SiO2. Minimum values were observed when carbon nanotubes were added at 0.4 and 0.6 wt. %. The morphology of worn surface is analyzed by optical microscopy for measuring the wear scare width as an indication for the wear rate. Minimum wear values were displayed by grease mixed by 50 % wight content of paraffin oil. Further increase in SiO2 content significantly increased wear due to their abrasive action. It was observed that combination of CNT/ SiO2 significantly increases of friction and wear. That can be explained on the bases that agglomeration of CNT increased their layers and shear stress. SiO2 showed relatively lower increase in friction due to the ball bearing effect of the nanoparticles.