Effects of temperature and rare earth content on oxidation resistance of Ni-based superalloy |
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Authors: | Xiu SONG Lei WANG Yang LIU and Hui-ping MA |
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Institution: | Xiu SONG~1,Lei WANG~1,Yang LIU~1,Hui-ping MA~2 1.Key Laboratory for Anisotropy and Texture of Materials,Northeastern University,Shenyang 110004,China,2.Department of High-temperature Materials,Central Iron & Steel Research Institute,Beijing 100081 |
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Abstract: | The oxidation behaviors of the Ni-22Cr-14W-2Mo superalloys with various La contents were investigated at 1 000 °C and 1 100 °C up to 500 h. The experimental results show that the oxidation resistance is improved by La addition. The mechanism of the reactive-element effect (REE) exhibits some difference at various oxidation temperatures. The REE is dependent on the solutionized La content when the alloy is oxidized at 1 000 °C. The dispersed LaCrO3
segregates on the grain boundaries of Cr-oxides, and hence the diffusion of metallic ions, e.g., Mn2+ and Cr3+, are prevented. The oxidation resistance decreases with the increase of La content. However, the REE ascribes not only to the solutionized La, but al so to the La-Ni intermetallic phases, when the alloy is oxidiz ed at 1 100 °C. The oxidation resistance is influenced by two effects: firstly, the formation of the dispersed La2O3 from the solutionized La on the grain boundary of Cr-oxides reduces the oxidation rate, a nd secondly, the aggregation of the La-O oxides from the large amount of La-Ni phases accelerates the oxidation process. The alloy with 0.026% La (mass fraction) exhibited excellent oxidatio n
resistance at 1100 °C. |
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Keywords: | Ni-based superalloy isothermal oxidation rare earth La oxidation resistance |
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