Study on High-Temperature Oxidation Behavior and Mechanisms of 3rd-Generation TiAl Alloys

Abstract:

The high-temperature environmental adaptability of TiAl alloys is crucial for the service safety of aero-engine low-pressure turbine blades. This study investigates the cyclic oxidation behavior of a cast ZTNM TiAl alloy at 650℃ and 750℃ in accordance with the HB5258 standard. The results indicate that the oxidation weight gain kinetics of the alloy at both temperatures follow a parabolic law. The oxidation rate at 650℃ (k′ = 0.0082 gm^-2h^-1) is lower than that at 750℃ (k′ = 0.0095 gm^-2h^-1), with both rates qualifying as "complete anti-oxidation" grade. The oxidation process comprises three distinct stages: the initial formation of a mixed TiO2 and Al2O3 scale; followed by the development of a continuous TiN/Ti2AlN nitride layer at the scale / metal substrate interface during the intermediate stage; and finally, the formation of an Al-depleted zone within the oxide scale after long-term exposure. The higher temperature (750℃) promotes the growth of TiO2, resulting in a thicker oxide scale. The nitride layer plays a critical role in determining the oxidation rate and the structural stability of the scale.