Effect of binder composition on corrosion behavior of Ti(C,N)-based cermets

Abstract:

Corrosion behavior of two Ti(C,N)-based cermets with 38 wt.% Ni or Ni–20Cr binder was investigated in 0.2 M H₂SO₄ and 0.2 M NaOH solutions at room temperature. In 0.2 M H₂SO₄ solution, there were significant differences in corrosion behavior and resistance between both cermets. For cermet with Ni–20Cr binder, binder phase was 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 occurred and current density steeply increased beyond the pseudo-passive region during potentiodynamic polarization, differing from cermet with Ni binder. By contrast, in 0.2 M NaOH solution, there were no significant differences in corrosion behavior and resistance between both cermets. For both cermets, ceramic grains were very slowly dissolved during immersion, accompanied by the formations of NiOOH and Cr^₆₊ compound, and no passivation but pseudo-passivation occurred during potentiodynamic polarization.