Tribological studies of dual-coating (intermediate hard with top epoxy-graphene-base oil composite layers) on tool steel in dry and lubricated conditions

The main objective of this investigation is to evaluate the tribological performance of dual-coatings of epoxy composites (epoxy with 10 wt% of graphene and 10 wt% of base oil) on different hard intermediate layers (diamond-like-carbon, tungsten carbide and titanium aluminium nitride) deposited on D2 steel. Friction and wear tests were conducted at 10 N and 15 N normal loads, and 0.63 m/s linear sliding speed and the counterface was a 4 mm steel ball. Among all dual-coatings, the combination of DLC intermediate layer and epoxy composite top layer furnished the least coefficient of friction of 0.09 and wear-life exceeded 2 x 10(5) cycles with no or negligible wear. In comparison, only hard or only soft coating had very limited wear-life.