中文摘要：

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246.8kJ/molDZ444合金氧化膜分为3层:外层为疏松的Cr、TiO和(Cr2的混合物;中间层为Cr内氧化物层为Al。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Cr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。

英文摘要：

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.