Tribological evaluation of N-phenylformamidino-N '-alkylthiocarbamides andtheir Mo-S complexes as EP lubricant additives

The tribological properties of 0.5% solutions of N-phenylformamidino-N'-alk ylthio-carbamides and their Mo-S complexes, i.e., mu-hydroxo-mu-(N-phenylfo rmamidino-N'-alkylthiocarbamido)-bis-(dioxohydroxo molybdenum VI) in paraff in oil were evaluated in a four-ball test. In particular, mu-hydroxo-mu-(N- phenylformamidino-N'-ethylthiocarbamido)-bis-[dioxohydroxo molybdenum VI] w as found to exhibit an appreciable increase in the load carrying capacity a nd values of flash temperature parameter, load wear index and pressure wear index and a decrease in the values of coefficient of friction. However, th e Mo-S additives did not markedly improve anti-wear characteristics in the wear tests. A comparative EP evaluation of mu-hydroxo-mu-(N-phenylformamidi no-N'-ethylthiocarbamido)-bis-(dioxohydroxo molybdenum VI) using steel bail s of different compositions, indicated its suitability of replacing alloy s teel balls with cheaper carbon steel balls. The topography of the wear scar s on the used steel ball specimen was studied by SEM.