第三代钛铝合金高温氧化行为及机理研究

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

摘要:

钛铝合金的高温环境适应性对航发低压涡轮叶片的服役安全有重要影响，本文以铸造钛铝合金ZTNM为研究对象，依据HB5258标准并结合循环氧化实验，系统研究了该合金在650 ℃和750 ℃循环氧化行为。结果表明，两种温度下合金的氧化增重动力学曲线均呈抛物线规律，650 ℃氧化速率（k′650℃=0.0082 g·m?2·h?1）低于750 ℃（k′750℃ =0.0095 g·m?2·h?1），且在两个温度下氧化速率均达到完全抗氧化级。氧化过程可分为三个阶段：氧化初期生成TiO?+Al?O?膜；中期在膜/基体界面处形成连续TiN/Ti?AlN氮化物层，长期则在氧化膜中出现贫Al区。更高温度（750 ℃）促进了TiO?的快速生长，使氧化膜更厚，氮化物层是决定氧化速率及氧化膜结构稳定性的关键因素。

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.