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.