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 1600A degrees C

摘要

The high-temperature oxidation of AlN-TiCrB (2) composites in air up to 1600A degrees C is studied in the composition range from 5 to 50 wt.% TiCrB (2) . The structure and phase composition of oxide layers formed in the temperature range 1200-1600A degrees C are determined by thermal gravimetry, metallography, electron microprobe analysis, and scanning electron microscopy. It is established that Ti-Cr-O lower solid solutions (Cr (2) Ti (7) O (7) and Cr (2) Ti (4) O (11) ), alpha-Al (2) O (3) , and TiO (2) (rutile) form in the temperature range 1200-1350A degrees C during oxidation of the samples. When temperature increases to 1500-1550A degrees C, the oxidation products contain Cr (2) TiO (5) , beta-Al (2) TiO (5) , and (AlCr (2) )TiO (3) . They form a homological series of isomorphic solid solutions, representing a fine self-reinforced oxide film, which leads to exceptionally high oxidation resistance (> 1600A degrees C) of the AlN-TiCrB (2) ceramic composites.