Effect of microstructure on the oxidation behavior of a β-solidified γ-TiAl based alloy after nitrogen ion implantation

The microstructure of the oxide layer of a β-solidifying γ-TiAl alloy (Ti-43.2Al-1.9V-1.1Nb-1.0Zr-0.2Gd-0.2B) after nitrogen ion implantation was studied after cyclic oxidation tests at 800 °C. Oxidation resulted in the formation of the continuous oxide scale, consisting of thin inner and outer TiO2, dense Al2O3 and mixed Al2O3 + TiO2 layers. It was revealed that the nitrogen ion implantation considerably inhibited the growth of the oxide scale, internal oxidation and Al-depleted zones. Thick Al-depleted zones and a mixture of Al2O3 and TiO2 were formed along the colony boundaries. Tooth-shaped Al-depleted zones propagated along the lamella boundaries. In addition, the presence of Gd-rich particles in the oxide scale promoted the formation of Al2O3 particles in surrounding areas and increased the depth of the oxide scale around.