1993 Volume 33 Issue 8 Pages 869-876
Oxidation resistance of TiAl coupons coated with IBED Si3N4 films of thicknesses of 0.5, 1 and 2 μm has been investigated by the cyclic oxidation test at 1300 K in a flow of purified oxygen at atmospheric pressure. The application of the nitride film of 0.5 μm thickness results in sufficiently good oxidation 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 Al2O3 and silicon compound beneath the outer TiO2 layer during the early oxidation period. However, this effect decreases as the film thickness increases. After around 10 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.
