(1. 沈阳理工大学 材料科学与工程学院，沈阳 110159；
2. 中国科学院 金属研究所，沈阳 110016)
摘 要: 用热重法研究稀土元素Y和Ce对定向凝固镍基高温合金 DZ444 高温氧化行为的影响，用X 射线衍射仪和扫描电镜等观察和分析氧化膜组成和形貌。结果表明：合金在 700、850和 950 ℃下的恒温氧化动力学均符合抛物线规律，稀土元素的添加对其无影响；然而，添加稀土元素使其氧化激活能由 257.6 kJ/mol 降低至 246.8 kJ/mol；DZ444合金氧化膜分为3层：外层为疏松的 Cr2O3、TiO2和(Cr0.88Ti0.12)2O3的混合物；中间层为Cr2O3；内氧化物层为Al2O3。稀土元素未改变合金氧化膜的组成。稀土元素极易偏聚在合金表面，促进保护性Cr2O3膜的形成，从而阻止合金的进一步氧化，并能有效抑制合金的内氧化。
关键字: 高温合金；稀土元素；高温氧化；定向凝固
（1. School of Materials Science and Engineering, Shenyang Ligong University, Shenyang 110159, China;
2. Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China）
Abstract:The effect of rare earth elements Y and Ce on the oxidation behavior of Ni-based superalloy DZ444 at elevated temperatures was studied by TGA method. The composition and morphology of the oxide films of DZ444 alloy were measured by XRD and SEM. The results indicate that rare earth elements has no effect on the oxidation kinetics, which obey parabolic law at 700, 850 and 950 ℃. However, the values of activation energy decrease from 257.6 kJ/mol to 246.8 kJ/mol when Y and Ce elements are added to the alloy. The oxide films of DZ444 alloy consist of three layers, loose upper layer consists of TiO2, Cr2O3 and (Cr0.88Ti0.12)2O3, compact intermediate layer is mainly Cr2O3, and discrete internal oxides are Al2O3. The composition of oxide films is not changed by rare earth elements, which can easily segregate on the surface of the alloy and accelerate the formation of protective oxidation film to prevent further oxidation. Therefore, it can be concluded that the addition of rare earth elements Y and Ce can effectively inhibit the development of internal oxidation.
Key words: superalloy; rare element; high temperature oxidation; directional solidification
