Tribological Improvement of Low-Viscosity Nanolubricants: MoO3, MoS2, WS2 and WC Nanoparticles as Additives

The aim of this research is studying the tribological performance of MoO3, MoS2, WS2 and WC nanoparticles as additives of PAO4. Pure sliding tribological tests were performed at 120 °C, finding outstanding friction and wear reductions in comparison with the PAO4, with maximum friction reductions of 64% for the 0.1 wt% MoS2 nanolubricant and greatest wear decreases for 0.1 wt% MoS2 nanolubricant: a width reduction of 62% and a worn area decrease of 97%. Raman mapping and a roughness evaluation of the worn pins confirmed the tribofilm formation and mending as tribological mechanisms. Rolling–sliding tests were conducted with best nanolubricants performance in pure sliding, observing excellent antifriction capabilities of MoS2 nanoparticles at low speeds, indicating that the use of nanoparticles is vital in boundary lubrication.