Densification and corrosion properties of graphite reinforced binderless TiC70N30 ceramic composites

In this study, binderless TiC70N30 ceramic composites with varying graphite (TiC70N30–Gr) reinforcements were fabricated via spark plasma sintering and their effect on densification was assessed. Subsequently, the electrochemical behaviour of TiC70N30–Gr composites was evaluated in 0.5 mol/L hydrochloric acid (HCl), 0.5 mol/L sulphuric acid (H2SO4) and 0.5 mol/L nitric acid (HNO3) solutions using open circuit potential, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) methods. The corrosion behaviour of TiC70N30- based ceramic composites with and without graphite reinforcement exhibited high corrosion resistance in the acidic electrolytes. Composites with 0.5 and 1.0 wt% graphite content showed lower Icorr values of 0.452 µA and 0.081 µA in 0.5 mol/L HCL and 0.5 mol/L HNO3, respectively, while specimen without graphite addition showed better corrosion resistance in 0.5 mol/L H2SO4 (0.041 µA). Based on the corrosion results, the corrosion properties of TiC70N30 ceramic composites in HCl and HNO3 solutions were significantly enhanced upon the incorporation of graphite reinforcements. However, the corrosion test results conducted in H2SO4 solution showed that the addition of graphite had a negligible influence on the corrosion resistance of the titanium carbonitride (TiCN) composites.