High-temperature oxidation of Ti{sub}3Al{sub}0.7Si{sub}0.3C{sub}2 compound at 900 and 1000℃ in air

摘要

The compound, Ti{sub}3Al{sub}0.7Si{sub}0.3C{sub}2, was synthesized by hot pressing a powder mixture of TiC{sub}x (x=0.6), Al and Si. Its oxidation at 900 and 1000℃ in air for up to 50 h resulted in the formation of rutile-TiO{sub}2, α-Al{sub}2O{sub}3 and amorphous SiO{sub}2. The oxide scales formed consisted of triple layers, viz, an outer TiO{sub}2 layer containing Al{sub}2O{sub}3 particles, an intermediate Al{sub}2O{sub}3 layer, and an inner mixed layer that was rich in TiO{sub}2, but deficient in Al{sub}2O{sub}3 and SiO{sub}2. During oxidation, Ti diffused outwards to form the outer TiO{sub}2 layer, and oxygen was transported inwards to form the inner mixed layer. At the same time, carbon was liberated from Ti{sub}3Al{sub}0.7Si{sub}0.3C{sub}2. Ti{sub}3Al{sub}0.7Si{sub}0.3C{sub}2 oxidized slower than the TiO{sub}2-forming kinetics, but faster than the (α-Al{sub}2O{sub}3 or SiO{sub}2)-forming kinetics.