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 (PO2 and PH2O) 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 TiO2.