Tribological roles of MoS 2 and PTFE nano oils at the rolling/sliding point contacts: Conventional versus textured contacts

Abstract

Nanolubricants and surface textures have evidenced the ability to improve the tribo-performances of concentrated contacts. Motivated by this finding as reported in the literature, in the present work, the synergistic uses of laser-created surface textures and nanolubricants have been employed to explore and improve the tribological behaviours of moderately loaded (P_H= 0.5 and 0.8 GPa) point contacts operating mainly in mixed and elastohydrodynamic lubrication regimes. MoS₂ and polytetrafluoroethylene (PTFE) nanoparticles based on two nanolubricants were prepared in the laboratory to lubricate the rolling/sliding conventional and textured point contacts. Two sets of contacts (grounded discs versus lapped balls and grounded textured discs versus lapped balls) have been employed to create the geometric configuration of conventional and textured concentrated point contacts. Based on the experimental results found herein, the friction coefficient with the textured contacts reduced by 64% in the presence of MoS₂-based nanolubricant as compared to the conventional point contact lubricated with the base oil; however, in the presence of polytetrafluoroethylene-based nanolubricant, this reduction has been recorded by 56%. The textured surface involving a small dimple size yielded better results than the relatively large size. Worn surfaces have been investigated and analysed using optical and scanning electron microscopy/energy dispersive X-ray spectroscopy micro-images. Moreover, certain surface studies using atomic force microscope have also been conducted to understand the surface topography and associated wear mechanisms.