Effects of sliding velocity and normal load on friction and wear characteristics of multi-layered diamond-like carbon (DLC) coating prepared by reactive sputtering

► Friction and wear characteristics of a Cr/CrN/a-C:H:W/a-C:H coating were examined. ► Friction coefficient decreases, as sliding velocity increases from 0.0625 to 2 m/s. ► Wear rate of DLC coating takes the maximum value at the 0.25 m/s of sliding velocity. ► Transfer layers were not sufficiently formed at sliding speeds below the 0.25 m/s. ► Graphitization and transfer of a-C:H affects the friction and wear characteristics.