Friction and wear behaviors of the complexes of rare earth hexadecylate as grease additive

Four complexes of rare earth hexadecylates (La, Pr, Sm, Gd) and copper hexadecylate were synthesized. Their tribological properties as additives in lithium grease were evaluated using a four-ball machine and a ring-block tester. The results indicated that these rare earth hexadecylates possessed antiwear and friction reduction properties in lithium grease. Their antiwear and friction reduction properties in lithium grease were better than that of copper hexadecylate. The lubricating mechanisms of the complexes as lithium grease additive were investigated using X-ray photoelectron spectroscopy (XPS). The results showed that tribochemical reaction happened during rubbing. The products of the tribochemical reaction were beneficial for improving the friction and wear behaviors of the lithium grease.