Tribological Behavior of Molybdenum Coordination Compound without Sulfur and Phosphorus as Oil Additive for Steel-steel Contact

A new kind of molybdenum coordination compound(MCC) without sulfur and phosphorus was prepared and evaluated as a promising lubricant additive for steel-steel contact.Tribological behavior of synthetic MCC as a lubrication additive for a steel-steel contact was comparatively investigated on SRV test rig with(ball-on-disc configuration),using paraffin as a comparison.The worn steel surfaces lubricated with paraffin and 1%MCC+paraffin under different loads were observed by scanning electron microscope,and the chemical states of some typical elements on the worn surfaces were analyzed by X-ray photoelectron spectroscopy.It was found that the synthesized MCC in the paraffin base oil significantly reduced friction coefficient and wear rate.Paraffin containing 1wt%MCC additive showed better friction-reducing and anti-wear abilities compared with paraffin without additives.Meanwhile hardness on worn surface,when lubricated with 1%MCC+paraffin,increased during friction and wear process,which contributed to reducing friction and wear of both tribo-pairs.Significant improvement of friction and wear,is due to action of the boundary layer and MCC deposited on the worn steel surface which prevent direct steel-steel contact from severe adhesion,scuffing,and seizure.