Effect of Binder Composition on Corrosion Behavior of Ti(C,N)-Based Cermets

Corrosion behavior of two Ti(C,N)-based cermets with 38wt% Ni or Ni-20Cr binder was investigated in 0.2 mol/L H2SO4 and 0.2 mol/L NaOH solutions at room temperature. In 0.2 mol/L H2SO4 solution, there are significant differences in corrosion behavior and resistance between both cermets. For cermet with Ni-20Cr binder, binder phase is very slowly dissolved during immersion, mainly due to that the spontaneous formations of NiO, Ni(OH)(x)(SO4)(y), Cr2O3 and Cr(OH)(3), and no passivation occurs and current density rapidly increases beyond the pseudo-passive region during potentiodynamic polarization, differing from cermet with Ni binder. By contrast, in 0.2 mol/L NaOH solution, there are no significant differences in corrosion behavior and resistance between both cermets. Ceramic grains are very slowly dissolved during immersion, accompanied by the formations of NiOOH and Cr6+ compound, and no passivation but pseudo-passivation occurs during potentiodynamic polarization.