TRIBOLOGICAL PERFORMANCE OF ANTIWEAR ADDITIVE DISPERSED IN HYDRAULIC OIL

The antiwear properties of hydraulic oils containing zinc dialkyl dithiophosphates are discussed. The tested additives are added to hydraulic oil at different concentrations. Tests were carried out to investigate the friction and wear of steel lubricated by these additives using pin on disc wear tester. The experiments of the present work reveals that friction coefficient significantly increased as the applied load increased. Addition of the additive into hydraulic oil decreased friction coefficient, where the lowest friction values were observed at 1.0 wt. % of the additive content. The same trend was observed when the test specimens were lubricated by relatively high viscosity hydraulic oil. Besides, wear decreased with increasing additive content. The lowest values were measured for the 1.0 wt. % additive content. The viscosity improver decreased the values of wear. The decrease of friction and wear can be attributed to the decomposition products of the additive that work as solid lubricants. While increasing the viscosity enabled the oil to form relatively thicker oil film between the sliding surfaces.