High-Temperature Oxidation of AlN-TiCrB sub(2) Composites in Air. II. Structure and Phase Composition of Oxide Layers Formed on AlN-TiCrB sub(2) Composites in Air up to 1600 degree C

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