Effect of Mo2C on electrochemical corrosion behavior of Ti(C,N)-based cermets

The electrochemical corrosion behavior of Ti(C,N)-based cermets with different Mo2C additions was investigated in freely aerated 10% H2SO4 and potentiodynamic polarization of all the materials was conducted from -0.5 to 1.5 V. There are two passive regions for all polarization curves. The first should be attributed to passive film formation due to Ti(C,N), while the second may be due to the presence of Ni. Corrosion current density increases with Mo2C content increasing, from 2.06×10-3 to 6.70×10-3 mA/cm2 . It is indicated that the corrosion resistance of Ti(C,N)-based cermets decreases with the increase of Mo2C addition. A skeleton of Ti(C,N) gains is observed after dissolution of Ni. The inner rim of cermets, rich in Mo2C, is corroded along with Ni binder and is more serious with the increase of Mo2C content. The secondary carbide Mo2C can be oxidized and dissolved in sulphuric acid.