High temperature in-situ X-ray diffraction study of the oxidation of the Ti3Al based alloys

High temperature in-situ X-ray diffraction was carried out to determine the oxidation behaviour of Ti3Al and Ti3Al based alloys at 700 degrees C and 800 degrees C, The weight gain curves were measured for the alloys. The distribution of elements on the cross section of the oxidation layer was also analyzed by electron probe. The results show that the oxidation rate is greatly reduced by alloying Nb and Si. TiO2 forms first during the oxidizing process. The oxidation layer of the binary Ti3Al is the mixture of TiO2 and Al2O3. Nb and Si additions improve the oxidation resistance of Ti3Al based alloys and promote the formation of TiN and TiAl layer on the surface of the Nb and Si alloyed Ti3Al, but does not promote the formation of Al2O3. The formation of continuous TiN layer which serves as a diffusion barrier is suggested to be the main reason for improving oxidation resistance.