Characterization of oxidation mechanisms in a family of polycrystalline chromia-forming nickel-base superalloys
Characterization of oxidation mechanisms in a family of polycrystalline chromia-forming nickel-base superalloys
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DOI：
10.1016/j.actamat.2021.116626
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发表时间：
2021-03
期刊：
影响因子：
9.4
通讯作者：
M. Lapington;D. Crudden;Roger C. Reed;Michael P. Moody;P. Bagot
中科院分区：
文献类型：
--
作者：
M. Lapington;D. Crudden;Roger C. Reed;Michael P. Moody;P. Bagot
研究了一系列具有不同Ti：Nb比的新型多晶镍基高温合金的氧化性能，结果表明，增加钛含量与加速氧化动力学之间存在相关性。使用SEM/EDX和原子探针断层扫描对所得氧化物层进行微观结构和化学的高分辨率表征，以精确定位氧化铬尺度内的Ti偏析，以确定解释这种相关性的潜在机制。尽管数据中存在一些差异，但溶解在氧化铬鳞片中的Ti水平与每种合金的标称Ti浓度或氧化性能几乎没有相关性，表明氧化速率不依赖于本体氧化铬中的掺杂剂水平。APT分析的目标是氧化皮内的许多晶界，因为已知这些晶界充当短路扩散路径。观察到Ti、Nb和Ta向氧化物晶界的偏析，这表明离子传输速率可以由存在于晶界处的掺杂剂而不是溶解在本体内来介导。
The oxidation properties of a family of novel polycrystalline Ni-based superalloys with varying Ti:Nb ratio have been studied, which has shown a correlation between increasing titanium content and accelerated oxidation kinetics. High-resolution characterization of microstructure and chemistry was carried out on the resultant oxide layers using SEM/EDX and Atom Probe Tomography to precisely locate Ti segregation within chromia scales, in order to identify a potential mechanism to explain this correlation. Despite some spread in the data, levels of Ti dissolved in the chromia oxide scales showed little correlation with the nominal Ti concentration or the oxidation properties of each alloy, indicating that oxidation rates are not reliant on dopant levels within bulk chromia. A number of grain boundaries within the oxide scale were targeted for APT analysis, as these are known to act as short-circuit diffusion paths. Segregation of Ti, Nb and Ta to oxide grain boundaries was observed, suggesting that ion transport rates may instead be mediated by dopants present at grain boundaries rather than dissolved within the bulk.