Effect of pre-oxidation on aluminized coating and their oxidation resistance of Ti alloy

The aluminized + pre-oxidized and pre-oxidized + aluminized Ti alloys are studied by SEM and XRD, respectively. The results show that the aluminized + pre-oxidized coating layer is composed of Al2O3 and AlTi3 phases, while the pre-oxidized + aluminized coating layer consists of Al2TiO5, Al5Ti3 and Al3Ti phases, and after oxidation they are both composed of Al2O3 and TiO2. A comparison has been carried out to show the influence of pre-oxidation upon the aluminized coating and their oxidation resistance. The oxidation kinetics shows that the weight change of pre-oxidized + aluminized sample is less than that of the aluminized + pre-oxidized sample. The whole thickness of the aluminized + pre-oxidized scale is about two times than that of the pre-oxidation + aluminized scale. Consequently the pre-oxidized + aluminized coating is an effective method to improve the oxidation resistance of Ti alloy.