Evaluation of 2,4-Dithiomalonamides as Extreme Pressure Additives in the Four-Ball Test

Four-ball tests using 12.7 mm diameter steel bearing balls were conducted to evaluate the load-carrying and extreme pressure properties of admixtures of paraffin oil with 1, 5-diaryl-2, 4-dithiomalonamides and a sulphur-phosphorus commercial additive (0.5 per cent wt/vol.). 1, 5-Di-p-methoxyphenyl-2, 4-dithiomalonamide exhibiting wear scar diameter and friction coefficient values of 0.58 mm and 0.058 at 100 kgf (ISL) and 2.18 mm and 0.077 at 500 kgf as compared to the values of 2.05 mm and 0.022 at 56 kgf (ISL) and 2.73 mm and 0.43 at 100 kgf for paraffin oil appeared to be most effective. The surface topography of the wear scars were examined by scanning electron microscope.