Performance evaluation of TiN duplex coated alloy tool steel sliding against an aluminum alloy under a transfer condition

The tribological evaluation of the titanium nitride (TiN) duplex coated alloy tool steel has been studied as a potential surface modification for tools used for plasticity processes of aluminum alloy. Dry sliding experiments on duplex treated alloy tool steel blocks against an aluminum alloy ring were conducted under an oxidation-limited condition simulating a tool surface where the transfer of aluminum alloy occurs. In the sliding experiments a transfer of aluminum alloy was predominant and little wear of the TiN-coating film took place. After sliding for a certain distance, however, shell-like chipping (large-chipping) appeared on the TiN film surface under the transferred layers, and which grew in the downstream direction to cause a macroscopic spalling of the film. The film life defined by the occurrence of large-chipping of size 50–100 μm, was markedly prolonged by tempering the nitrided substrate. Possible mechanisms of the life improvement are discussed.

► Dry sliding experiment of TiN duplex coating in a transfer situation.
► The film shows the fatigue failure of macro-chipping under the transfer layer.
► The failure resembles the actual failure of the extruding die bearing.
► The tempering of nitrided layer before coating prolongs the film life.
► The elongation of the life is caused by the improvement of the interfacial strength.