Binder mediated enhanced surface adhesion of cured dry solid lubricant on bearing steel for significant friction and wear reduction under high contact pressure

Abstract

A new thermally cured polymer-graphene-zinc oxide-based solid lubricant is developed that reduces friction and wear significantly during the sliding wear of bearing steel under extreme contact pressure and long duration. The dry solid coating composite was made from a mixture of graphene, zinc oxide, and a specific industrial binder and then laminated on the surface of 52100 steel disks using the spin-coating technique. A ball-on-disk apparatus set to 1 GPa Hertzian pressure and a sliding distance of 500 m was used to examine the tribological properties of the coating. After ∼3000 cycles, the 15 μm thick coating created a significant reduction in the steel's coefficient of friction (approximately 82%) and wear loss compared to the uncoated surfaces. Following the triboligical examination, scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, and Raman spectroscopy were conducted to determine the topography and morphology of the composite coating and resultant wear scars. It is revealed that the persistent protective coating on the disk surfaces was attributed to the adhesion influence of interfacial zinc oxide and graphene on the contact surfaces. Scratch testing of the new composite demonstrated a significant improvement in its adhesive properties on bulk interfacial surfaces compared to previously studied coatings.