Electrified four-ball testing of ZDDP and MoDTC as additives in low-viscosity synthetic oil

Additives play an important role in the tribological performance of lubricants used in internal combustion engine (ICE) vehicles. As we are in the process of rapid transition from ICE vehicles to electric vehicles (EVs), the tribological performance of lubricants under electrified conditions has lately become an important concern since shaft currents have been shown to adversely affect the operation of bearings and gears by accelerating wear, scuffing, and fatigue failures. However, little work has been published on the lubricity performance of additives under electrical conditions. Therefore, this work aims to provide an evaluation of the tribological behavior of common additives such as zinc dialkyldithiophosphate (ZDDP), molybdenum dithiocarbamate (MoDTC), and their blend in a low viscosity synthetic oil (PAO4) in terms of friction and wear of AISI 52100 steel by conducting non-electrified (ASTM-D4172) and electrified four-ball tests. The blends were characterized in terms of electro-rheology, dielectric breakdown voltage (DBV), and tribological characteristics under boundary lubrication conditions. The worn surfaces were analyzed in detail by EDS and Raman spectroscopy. Overall, the addition of ZDDP and MoDTC to PAO4 was able to generate a lower coefficient of friction (CoF) and wear under boundary-lubricated conditions in both non-electrified and electrified sliding environments. © 2025 Elsevier B.V.

Electrified four-ball testing of ZDDP and MoDTC as additives in low-viscosity synthetic oil Academic Article in Scopus