Load-dependent transition in sliding wear properties of TiCN-WC-Ni cermets

The present investigation aims at evaluating the sliding wear behavior of TiCN-20 wt%Ni cermets, containing varying amounts of WC (5-25 wt%) against 100Cr6 steel at different loads (5, 20, and 50 N). The dominant wear mechanisms were established by using surface topography analysis (Stylus profilometry), scanning electron microscopy, and X-ray diffraction. The steady-state coefficient of friction varies over a wide range: 0.73-0.27 at different loads for the investigated cermets. The volumetric wear loss of the cermets in general increases with load, while the wear rate varies in the order of 10(-7) mm(3).(N.m)(-1). The worn surface characterization reveals that a transition in wear mechanism occurs from abrasion and mild tribo-oxidation at low loads to the formation of a dense tribo-oxide layer, containing oxides of Fe and Ti (essentially Fe9TiO15) at high loads. Efforts have been made to discuss the possible reaction pathways to explain the formation of the tribochemical layer. The addition of WC to TiCN-Ni-based cermets results in increased abrasion at low loads and severe fracture of the tribo-oxide layer at high loads.