Tribological properties and lubricating mechanisms of the rare earth complex as a grease additive

One N-salicylidene derivative of malonic dihydrazide (Schiff base) and its complexes of lanthanum and copper were synthesized. Their tribological properties as additives in lithium grease were evaluated using a four-ball machine. The results indicate that these compounds possess good load-carrying capacity, friction reduction, and anti-wear properties. In particular, the complex of lanthanum has excellent load-carrying capacity, similar to those of zinc dialkyldithiophosphate and molybdenum dialkyldithiocarbamate, and exhibits good anti-wear property. The thermal stability of these compounds were investigated with a thermal gravity analyzer. The lubricating mechanism of these compounds as additives in lithium grease was investigated with analytical tools such as an electron probe micro-analyzer and an Auger electron spectroscope.