High-Temperature Oxidation of AlN–TiCrB₂ Composites in Air.
II. Structure and Phase Composition of Oxide Layers Formed on AlN–TiCrB₂ Composites in Air up to 1600 °С

Abstract

The high-temperature oxidation of AlN–TiCrB₂ composites in air up to 1600 ºC is studied in the composition range from 5 to 50 wt.% TiCrB₂. The structure and phase composition of oxide layers formed in the temperature range 1200–1600 ºC are determined by thermal gravimetry, metallography, electron microprobe analysis, and scanning electron microscopy. It is established that Ti–Cr–O lower solid solutions (Cr₂Ti₇O₇ and Cr₂Ti₄O₁₁), α-Al₂O₃, and TiO₂ (rutile) form in the temperature range 1200–1350 ºC during oxidation of the samples. When temperature increases to 1500–1550 ºC, the oxidation products contain Cr₂TiO₅, β-Al₂TiO₅, and (AlCr₂)TiO₃. They form a homological series of isomorphic solid solutions, representing a fine self-reinforced oxide film, which leads to exceptionally high oxidation resistance (>1600 ºC) of the AlN–TiCrB₂ ceramic composites.