Electrochemical behavior of TiCN-Ni-based cermets

Abstract

The electrochemical behavior of TiCN-20 wt% Ni cermets containing different secondary carbides (10 wt% WC, NbC, TaC, and HfC) was investigated in freely aerated 0.2 mol/L sulfuric acid. A comparison has also been made with polarization behavior of pure Ni. All the materials (except HfC-containing cermet) exhibited active-passive polarization behavior, characterized by two passive regions. The first passive region, obtained on polarizing past the zero current potential, was attributed to passive film formation due to TiCN, while the second passive film is presumably due to the presence of a Ni binder phase. The passivation behavior in the case of cermets containing various secondary carbides (WC, TaC, and NbC) was similar to base-line TiCN-20Ni cermets, while poor passivation behavior was observed in the case of TiCN-20Ni-10HfC. Efforts have been made to correlate the passivation behavior with the microstructural characteristics of sintered cermets. © 2006 The American Ceramic Society.