(1. 沈陽理工大學(xué) 材料科學(xué)與工程學(xué)院，沈陽 110159；
2. 中國科學(xué)院 金屬研究所，沈陽 110016)
摘 要: 用熱重法研究稀土元素Y和Ce對定向凝固鎳基高溫合金 DZ444 高溫氧化行為的影響，用X 射線衍射儀和掃描電鏡等觀察和分析氧化膜組成和形貌。結(jié)果表明：合金在 700、850和 950 ℃下的恒溫氧化動力學(xué)均符合拋物線規(guī)律，稀土元素的添加對其無影響；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合金氧化膜分為3層：外層為疏松的 Cr2O3、TiO2和(Cr0.88Ti0.12)2O3的混合物；中間層為Cr2O3；內(nèi)氧化物層為Al2O3。稀土元素未改變合金氧化膜的組成。稀土元素極易偏聚在合金表面，促進(jìn)保護(hù)性Cr2O3膜的形成，從而阻止合金的進(jìn)一步氧化，并能有效抑制合金的內(nèi)氧化。
關(guān)鍵字: 高溫合金；稀土元素；高溫氧化；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
