Oxidation of HIPed TiC Ceramics in Dry O2, Wet O2, and H2O Atmospheres
Abstract:Isothermal oxidation of dense TiC ceramics, fabricated by hot-isostatic pressing at 1630°C and 195 MPa, was performed in Ar/O2 (dry oxidation), Ar/O2/H2O (wet oxidation), and Ar/H2O (H2O oxidation) at 900°–1200°C. The weight change measurements of the TiC specimen showed that the dry, wet, and H2O oxidation at 850°–1000°C is represented by a one-dimensional parabolic rate equation, while the oxidation in the three atmospheres at 1100° and 1200°C proceeds linearly. Cross-sectional observation showed that the dry oxidation produces a lamellar TiO2 scale consisting of many thin layers, about 5 m thick, containing many pores and large cracks, while H2O-containing oxidation decreases pores in number and diminishes cracks in scales. Gas evolution of CO2 and H2 with weight change measurement was simultaneously followed by heating the TiC to 1400°C in the three atmospheres. Cracking in the TiO2 scale accompanied CO2 evolution, and the H2O-containing oxidation produced a small amount of H2. A piece of single crystal TiC was oxidized in 16O2/H218O to reveal the contribution of O from H2O to the oxidation of TiC by secondary ion mass spectrometry.
Document Type: Research Article
Publication date: 2006-04-01