High-temperature Oxidation Resistance of TiAl Improved by IBED Si3N4 Coating.

Abstract

Oxidation resistance of TiAl coupons coated with IBED Si3N* films of thicknesses of 0.5. I and 2um has been investigated by the cyclic oxidation test at 1 300 K in a flow of purified oxygen at atmospheric pressure. Theapplication of the nitride film of 0.5 um thickness results in sufficiently goodoxidation resistance; the protective scale is maintained for at least 30 cycle (600 h) . The excellent oxidation resistance is attributable to the formation of a layer rich in Al203 and silicon compoundbeneath the outer TiO. Iayer during the early oxidation period. However, this effect decreases as the film thickness increases. After around IO cycle oxide scales spalled off over relatively large areas. The local fracture of the coating films during the early oxidation period was considered to be responsible for their limited effect.