Dry sliding and boundary lubrication performance of a UHMWPE/CNTs nanocomposite coating on steel substrates at elevated temperatures

A nanocomposite polymer coating of ultra-high molecular weight polyethylene (UHMWPE) reinforced with 0.1 wt% of single-walled carbon nanotubes (SWCNTs) is developed and coated onto steel substrates for a possible application as a boundary lubricant in bearings and gears. Since temperature is one of the predominant factors in determining the tribological performance of polymer coatings, friction and wear experiments were carried out at elevated temperatures. Experiments are performed on a custom-built tribometer simulating high contact pressures under dry and base oil lubricated conditions. Wear mechanisms of the nanocomposite coating and the counterface material are studied using optical profilometry. FESEM images are used to study the wear morphology of the coating. Possible changes in the crystallinity of the polymer due to temperature changes are studied by XRD. It is observed that the addition of SWCNTs to the polymer matrix not only helps in improving the mechanical properties such as hardness and the load bearing capacity of the coating but also enhances its frictional and wear properties at elevated temperatures.