The synergistic antiwear and frictional properties of organic molybdenum compound with zinc dialkyldithiophosphate

The synergistic antiwear and friction reducing properties of oils containing nor-sulfur nor-phosphoruorganic molybdenum compound (MC) with zinc dialkyldithiophosphate (ZnDDP) were evaluated by four ball tester. The results show that the combination of organic molybdenum compound and ZDDP exhibits good synergistic antiwear and friction reducing properties. Moreover, at the same concentration of ZDDP with different alkyl groups, there was an different optimum MC concentration for better antiwear and friction reducing properties. When MC concentration exceed this optimum valves, the antiwear and friction reducing properties of lubricants were not improved obviously. However, These properties were affected significantly by ZDDP type, while the effect of ZDDP type on these properties became small at higher MC/ZDDP ratios. Especially, the combination of MC with ZDDP containg primary C8 alkyl groups is very effective on tribological behaviours under lower dosage of MC added to oils. Finally, the surface analysis indicated that Mo, S atoms are distributed evenly on the wear scar, which contribute to improve the tribological properties of lubricants.