Effects of Total Base Number and Borate on the Calcium Detergent MoDTC Synergy in Tribofilm Formation

Abstract Detergents and anti-wear additives are both essential components of engine oil. Among the latter, molybdenum dialkyldithiocarbamate (MoDTC) is a prominent example. The synergistic effects of four calcium detergents with MoDTC were tested using a block-on-ring configuration under two specific conditions. The results indicate that a relatively high Total Base Number promotes the formation of MoO3-CaCO3 binary matrix, thereby accelerating the development of MoDTC-derived tribofilm. Replacing 25% of the nanoparticles with calcium borate further accelerates the film formation under low-speed/high-load condition, leading to promoted anti-wear and friction-reduction performance. These findings are of considerable significance to the design of lubricant formulations.