PROTECTIVENESS OF A CVD-AL2O3 FILM ON TIAL INTERMETALLIC COMPOUND AGAINST HIGH-TEMPERATURE OXIDATION

TiAl coupon specimens coated with Al2O3 films by a CVD technique were oxidized in a flow of purified oxygen at atmospheric pressure for 100 ks at 1073, 1173 and 1273 K. The mass gains due to the oxidation were negligible. The CVD Al2O3 films of about 3-mu-m thickness were protective and very adherent to the substrate even after the oxidation at all the temperatures tested except 1273 K. Irregularly shaped Al2O3 crystals grew on the specimen at 1273 K even though they were very small, showing a limited protection at this temperature.