High temperature oxidation of sintered TiC in an H₂O-containing atmosphere

Isothermal oxidation of sintered titanium carbide (TiC) ceramics produced by HIP processing was carried out at temperatures of 900 to 1200 °C for 1 to 50 h in O₂/Ar (dry oxidation), O₂/H₂O/Ar (wet oxidation) and H₂O/Ar (H₂O oxidation) with oxygen and water partial pressures (P_O2 and P_H2O) of 5 kPa. The oxidation kinetics were described by a diffusion-limited rate equation in dry atmospheres and by an interfacial reaction-limited rate equation, following an early stage diffusion-limited reaction in wet and H₂O atmospheres. Some inflection points were observed on the isothermal oxidation curves due to the formation of cracks, as observed by SEM. The oxidation rates at 900 °C in dry and wet atmospheres were not greatly changed, but slightly accelerated in H₂O. At 1000 °C, the oxidation rates became higher in the order of H₂O>wet>dry atmosphere. Above 1100 °C, the oxidation rates were almost the same as in wet and H₂O atmospheres, but higher than in the dry condition. X-ray diffraction (XRD) analysis showed that the oxide scale obtained under all conditions consisted of TiO ₂.