The influence of Ni3Al binder content on the aqueous corrosion response of TiC and Ti(C,N) cermets

In the current work the corrosion mechanisms of Ti(C,N) based cermets are analysed in a 3.5 wt.% NaCl aqueous solution. The effects of varying the Ni3Al intermetallic binder content are assessed, with either 20 or 30 vol.% binder used. The assessment of corrosion involved a variety of electrochemical measurements, including open circuit potential, along with anodic and cathodic potentiodynamic polarisation. Both the corrosion potential and current density were determined from Tafel extrapolation, which allowed an estimation of the cermet corrosion rates. It is demonstrated that the primary corrosion mechanism for these cermets involves dissolution of the intermetallic phase during oxidation attack, and thus this response increases with the amount of binder in the cermet. It was also observed that addition of N to the Ti(C,N) ceramic phase is beneficial to the corrosion characteristic the cermets, due to significant refinement of the grain size of the hard phase.