A study in the tribochemistry of alkyldithiobiurets and their Mo-S complexes as EP additives

Abstract

0.5% solutions of 1-alkyl-2,4-dithiobiuret ligands and their Mo-S complexes i.e. μ-hydroxo-μ-(1-alkyl-2,4-dithiobiureto)-bis-[dioxohydroxo molybdenum-(VI)] in paraffin oil were found to significantly reduce wear and friction of 12.7 mm diameter steel balls in a four-ball test. In particular, the additive μ-hydroxo-μ-(1,1-dimethyl-2,4-dithiobiureto)-bis[dioxohydroxo-molybdenum- (VI)] was found to exhibit an appreciable increase in the load carrying capacity of the lubricant and a decrease in the values of coefficient of friction. The additive μ-hydroxo-μ-(1,1-dimethyl-2,4-dithiobiureto)-bis[dioxohydroxo- molybdenum(VI)] was also found to be effective at high speeds. The topography and tribochemistry of the used ball specimens were examined by means of scanning electron microscopy and scanning auger electron spectroscopy techniques, respectively. © 1997 Elsevier Science S.A.