Features of corrosion resistance of AlN-SiC ceramics in air up to 1600 degrees C

The kinetics and mechanism of (80% AIN + 20% SiC) and (50% AIN + 50% SiC) p owders and ceramics oxidation in air up to 1600 degrees C Mere studied with the aid of TG, DTA, XRD, EPMA, SEM and metallographic analysis methods. Th e ceramics samples were obtained by, hot pressing fine-dispersion AIN and S iC powders with an average particle size of I mu m at 1800 degrees C for 2 h. This ensures a fine-grain material structure with a uniform distribution of phase components. It was shown that in a non-isothermal regime, a three -stage oxidation mechanism takes place. It,was established that the scale f ormed consists of three oxide layers. lit the inner layer, Al10N8O2 oxynitr ide and beta-SiO2 (cristobalite) phases were observed, in the intermediate layer, beta-SiAlON uas found for samples with a relatively, low SiC content whereas alpha-Al2O3 was present in samples with a greater SiC content. The outer lay er contains 3Al(2)O(3 .)2SiO(2) (mullite) as a main phase, the l atter ensuring highly protective properties of the scale. The Materials inv estigated call be considered as having extremely high resistance to corrosi on up to 1550 degrees C. (C) 1999 Elsevier Science Limited. All rights rese rved.