Study on High-Temperature Oxidation Behavior and Mechanisms of ZTNM TiAl Alloys

Abstract:

The cyclic oxidation behavior of a cast ZTNM TiAl alloy at 650 and 750 ℃ in accordance with the HB5258 standard was investigated. The results indicate that the oxidation mass gain kinetics of the alloy at both temperatures follows a parabolic law. The oxidation rate at 650 ℃ (k''= 0.0082 g?m^-2?h^-1) is lower than that at 750 ℃ (k''= 0.0095 g?m^-2?h^-1), with both rates qualified as “complete anti-oxidation” grade. The oxidation process contains three distinct stages: the initial formation of a mixed TiO₂ and Al₂O₃ scale; the development of a continuous TiN/Ti₂AlN nitride layer at the scale/metal substrate interface during the intermediate stage; 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.