The synergistic effect of novel anti-wear additive 1,3,4-thiadiazole mixed ammonium salt and MoDTC on tribological properties of FeCoCrNiMn alloy

To meet the increasingly stringent environmental requirements, we propose incorporating nitrogen-containing compounds into the anti-wear additives in order to minimize the use of sulfur and phosphorus elements. On the other hand, FeCoCrNiMn layers, due to their excellent mechanical properties, exhibit potential application in wear-resistant coatings, but the mechanism of their interaction with anti-wear additives and molybdenum dithiocarbamate (MoDTC) has not been clarified. In this paper, a novel nitrogen-phosphorus-sulfur anti-wear additive of 1,3,4-thiadiazole mixed ammonium salt (TAS) was synthesized, and effects of TAS in combination with commercially available anti-wear additives (triphenyl phosphorothionate (TPPT), zinc dialkyldithiophosphate (ZDDP), and sulfurized isobutylene (T321)) and MoDTC on tribological properties of FeCoCrNiMn layers were investigated. The friction coefficient and wear rate of T321 were the lowest among the four anti-wear additives, at 0.112 and 4.13 × 10−6mm3/Nm, respectively, whereas those of MoDTC + T321 were 0.154 and 8.28 × 10−6 mm3/Nm. XPS analysis indicated that a high concentration of sulfur ions in the MoDTC + T321 can form MoS3 and MoSxOy, inhibiting the formation of MoS2, suggesting an antagonistic effect. Conversely, the tribofilm of MoDTC + TAS is composed of MoS2, phosphates, and organic amines, exhibiting the excellent anti-wear properties.