Tribological performance of DLC coatings deposited by ion beam deposition under dry friction and oil lubricated conditions

Understanding the reaction between lubricant additives and diamond-like carbon coatings is imperative for the improvement of the friction and wear properties of mechanical parts with diamond-like carbon coatings. Diamond-like carbon coatings were deposited with ion beam deposition and the influence of lubricant additives on the friction coefficients and wear rates of diamond-like carbon coatings under the lubricated conditions was studied. It was revealed that the wear rates of diamond-like carbon coatings under unlubricated conditions are 1.5 × 10−14 m3/(Nm) while they are decreased to 3 × 10−17 m3/(Nm) to 1.7 × 10−16 m3/(Nm) when lubricated by PAO-4 base oil with three additives. The addition of molybdenum dithiocarbamate in PAO-4 base oil decreases the friction coefficients of diamond-like carbon coatings to 0.07, but increases the wear rate of diamond-like carbon coatings. The addition of zinc dialkyl dithiophosphate to PAO-4 can slightly decrease the friction coefficient of diamond-like carbon coatings and improve the wear resistance of diamond-like carbon coatings. The addition of amine sulfuric-phosphate diester in PAO-4 can greatly decrease the wear rate of diamond-like carbon coatings to 3 × 10−17 m3/(Nm) but has a negligible effect on the friction coefficients of diamond-like carbon coatings. ► Effect of lubricant additives on tribological properties of DLC coating was studied. ► The studied lubricant additives were MoDTC, ZDDP, and T307. ► MoDTC reduces friction coefficient while increases wear rate. ► ZDDP and T307 improve wear resistance of DLC.