BT25Y钛合金在600 ℃—800 ℃的高温氧化行为研究

Study on high temperature oxidation behavior of BT25Y titanium alloy at 600 ℃-800 ℃

摘要:

研究了BT25Y钛合金在600 ℃、700 ℃和800 ℃下的高温氧化行为。采用连续氧化增重法,并结合氧化速度常数、氧化活度等理论计算了合金的氧化动力学和热力学规律；利用XRD、SEM和EDS等表征方法研究了氧化膜的相结构和表面、截面形貌及元素分布。结果表明：BT25Y钛合金在600 ℃和700 ℃均有较好的抗氧化性能,其连续氧化动力学曲线符合抛物线规律,氧化层由细小TiO₂和Al₂O₃组成,氧化膜可有效阻止氧渗入基体,降低氧化速度；BT25Y钛合金在800 ℃氧化严重,其连续氧化动力学曲线近似符合直线规律,氧化层由Al₂O₃层和TiO₂层交替组成,氧化膜疏松多孔,不能有效阻挡氧向基体一侧的扩散。

关键词:BT25Y钛合金;高温氧化;氧化动力学;微观结构

Abstract:

The high temperature oxidation behavior of BT25Y titanium alloy was studied at 600 ℃, 700 ℃and 800 ℃. The thermodynamics and kinetics of the alloy oxidation were calculated by the method of continuous oxidation weight gain, the oxidation rate constant and the oxidation activity. The phase composition, surface and cross-section morphologies and elemental distribution of the oxide scale were respectively investigated by XRD, SEM and EDS. The results showed that BT25Y titanium alloy exhibited good oxidation resistance at 600 ℃and 700 ℃, and their oxidation kinetics curves followed the parabolic law. The continuous oxide scale composed of fine TiO₂ and Al₂O₃ particles can effectively prevent oxygen from infiltrating into the matrix and then remarkably reduce the oxidation rate. At 800 ℃, the oxidation behavior of the BT25Y titanium alloy was catastrophic, and its oxidation kinetics approximately followed the linear law. The oxide layer was alternately composed of Al₂O₃ layer and TiO₂ layer, and the oxidation film was loose and porous, which cannot effectively prevent the diffusion of oxygen into the matrix.

Key words:BT25Y alloy; high temperature oxidation; oxidation kinetics; microstructure