s Nouri - MAPNA Group, TUGA, Tehran, Iran
m Mirghorbani - MAPNA Group, TUGA, Tehran, Iran
h Pourfarzaneh - MAPNA Group, TUGA, Tehran, Iran

In the present research work, the high temperature oxidation resistance of two grades of -TiAl advancedalloy including Ti-۴۸Al-۲Nb-۲Cr (at. %) and Ti-۴۵Al-۲Nb-۲Mn-۱B (at. %) was compared via isothermaloxidation test at ۱۱۲۳K for ۲۰۰ hours. The isothermal oxidation test results indicate that industrial gradeof Ti-۴۸Al-۲Nb-۲Cr (at. %) possesses a better oxidation resistance and more desirable oxide scalesadherence compared to Ti-۴۵Al-۲Nb-۲Mn-۱B (at. %) alloy. The detailed microstructural and phaseidentifications of the formed oxide scales on two different grades of -TiAl alloy were performed usingSEM and XRD techniques. According to the obtained results in this work, it is observed that the structureof oxide scales that formed on both types of -TiAl alloys contains two separate layers including an outerTiO۲ layer and an inner layer of mixed TiO۲+Al۲O۳. Additionally, it is observed that there is an Aldepletedzone under the inner layer which may be created due to the outward diffusion of Al from thesubstrate to the outer oxide scales. Also, it was observed that there is no void in the oxide scale formed onTi-۴۸Al-۲Nb-۲Cr (at. %) alloy, while in Ti-۴۵Al-۲Nb-۲Mn-۱B (at. %) counterpart, several voids areobserved in the associated oxide scales. It seems that the relatively better oxidation resistance of Ti-۴۸Al-۲Nb-۲Cr (at. %) industrial grade is owing to presence of Cr in this alloy.

-TiAl alloy, Isothermal oxidation, Oxide scales, Microstructure.