THE EFFECTS OF FE, CU AND AL IMPURITIES ON THE OXIDATION RESISTANCE OF TISI2 .3. AL

The effect of aluminum on the oxidation resistance of titanium disilic ide (TiSi2) was investigated. The aluminum was mixed with titanium dis ilicide powder, compacted and then sintered. The compacts were oxidize d at elevated temperatures for various times. The oxide coatings were examined by thin film diffractometry and also in a scanning electron m icroscope equipped with energy dispersive spectroscopy. The oxidation of TiSi2 containing aluminum resulted in a porous, non-protective coat ing of mullite at temperatures of 1000-degrees-C and below. However, p re-oxidation at higher temperatures produced a more dense, protective mullite which showed adequate resistance to oxidation at the lower tem peratures. Parabolic kinetics with an activation energy of 20 kcal mol -1 were observed. However, intergranular oxidation of an aluminum-rich phase resulted in the severe degradation of the material's strength.