Comparing tribological behaviors of sulfur- and phosphorus-free organomolybdenum additive with ZDDP and MoDTC

A new kind of sulfur- and phosphorus-free organomolybdenum oil-based additive N, N-bis (2-hydroxyethyl)-dodecanamide molybdate (NNDM) was prepared. Its tribological performances as additive in base oil 150SN were examined on a four-ball tester, and compared with those of ZDDP and MoDTC under boundary lubrication condition. The tribofilm NNDM generated on the worn surface was analyzed by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Results showed that NNDM blend oil exhibited excellent load-carrying capacity, significantly reduced friction coefficient and wear rate of worn surface, which could be attributed to high amount of long-chain alkylamide and MoOx in NNDM tribofilm.

► Sulfur- and phosphorus-free molybdenum-containing additive was synthesized. ► Its tribological behaviors were evaluated comparing with ZDDP and MoDTC. ► The synthesized additive blend oil has good anti-wear and friction-resistance behaviors. ► The unique tribological performances are ascribed to high amount of long-chain alkylamide and MoOx in the tribofilm.