Synergistic effect of diisopropyl phosphite and over-based calcium sulphonate additives on tribological properties of AISI 52100 steel/Al 2O 3 ceramics

The friction-reducing and anti-wear effect of the 500SN base oil containing diisopropyl phosphite (T451) and over-based calcium sulphonate (KT5447) on AISI 52100 steel/Al2O3 ceramic were investigated with a ball-on-disc tribometer at a light load of 200 N and a high load of 400 N. The results indicate that the 500SN base oil containing T451 and KT5447 appears to have a synergistic effect on the pair. For the light load of 200 N, the effective composition is 3 wt% T45I + 2-3 wt% KT5447. For the high load of 400 N, the combination of T451 and KT5447 appears to have a synergistic friction-reducing and anti-wear effect. The scanning electron microscope images show that ploughed grooves, pitting, spalling and corrosion are the dominant wear modes for both 200 and 400 N. However, no evidence for the formation of the expected sulphur-containing or phosphorus-containing chemical compound is found according to X-ray photoelectron spectroscopy analysis of the worn steel ball surface at both loads. Copyright (C) 2011 John Wiley & Sons, Ltd.