Extreme pressure study of multi-walled carbon nanotube additives in water based lubricants

Monica Herrera-Maldonado, Luisana Contreras, Ángel G. Romero-Cantú, Oscar E. Montemayor, Karen Nava-Montemayor, Laura Peña-Parás, Demófilo Maldonado-Cortés, Oxana Kharissova, Patsy Arquieta

Abstract

The study of different nanoparticles as lubricant additives for extreme pressure applications have been on constant investigation due to the improvements on tribological performance. In this study, functionalized multi-walled carbon nanotubes (MWNTs) with carboxylic acid (COOH) and hydroxyl (OH) groups were dispersed into two lubricating fluids, distilled water and a water-based synthetic lubricant. MWNT-COOH and MWNT-OH were added at concentrations of 0.01, 0.1, 0.5, 1.0, 1.5 and 2.0 wt.% dispersing them by ultrasonication. Tests were performed on a four-ball T-02 tribotester according to the ITEePib Polish method for testing lubricants under conditions of scuffing. Wear scar diameters (WSD) were measured with an optical microscope. Results showed that MWNT-OH and MWNT-COOH outstandingly enhanced the load-carrying capacity (Poz) of the water-based synthetic lubricant by 743% and 681%, respectively. The results found in this study demonstrate that the addition of nanoparticles can improve the load-carrying capacity of lubricants and result in a better performance for extreme pressure applications in metal-forming processes.