Wear performance of bulk oriented nanocomposites UHMWPE/FMWCNT and metal-polymer composite sliding bearings

Abstract

Traditional metal-polymer sliding bearings have low cost and may operate under conditions of dry sliding friction; however, the wear rate of such bearings can be unacceptably high. This work tests the hypothesis that applying a layer of bulk oriented, polymer-based nanocomposites can reduce both the friction coefficient and wear rate. Bulk oriented nanocomposites based on ultra-high molecular weight polyethylene (UHMWPE) and fluorinated carbon nanotubes were prepared and their wear performance against AISI 304 stainless steel was compared using a rotating ring-in-bushing arrangement. The effects of supramolecular structure, surface roughness, mechanical properties, and carbon nanotubes additions on the COF and energetic wear rate of the materials were studied. The wear surface features were studied using scanning electron microscopy. The coefficient of dry friction (COF) was investigated over a range of loadings from 9.64 to 16N. An average COF of bulk oriented nanocomposites decreased by 70% (at a load of 9.64N) in contrast to the UHMWPE matrix material. Localized fatigue wear of polymer layers on the UHMWPE having an isotropic structure were observed. Additions of carbon nanotubes and the formation of nanofibrillar structure facilitated the development of a smooth wear surface. There was a significant effect of nanotubes on the sliding COF and energetic wear rate. An extremely low COF (0.046) was obtained at a load of 57.3kPa for the metal-polymer composite bearing surface against stainless steel. Finally, a new technology to manufacture metal-polymer composite sliding bearings using a layer of oriented nanocomposites was proposed