Qian Kun, Qu Shasha, Shu Lei, Xue Peng, Li Xiaobing, Chen Bo, Liu Kui
Jihua Laboratory, Foshan 528200, China.
Guangdong Institute of Special Equipment Inspection and Research, Guangzhou 510620, China.
Materials (Basel). 2022 Aug 24;15(17):5833. doi: 10.3390/ma15175833.
The high-temperature oxidation behaviors of polycrystalline Co-30Ni-10Al-4W-4Ti-2Ta superalloys with Cr contents ranging from 1 to 5 at.% are characterized at 900 °C to provide benchmark data for the alloy design of the CoNi-based superalloys. The mass gain curves for all three alloys exhibit parabolic growth, and the addition of 5Cr at.% is sufficient to decrease the oxidation rate by two orders of magnitude compared to the Cr-free alloy. Furthermore, cross-sectional findings reveal that these three alloys form qualitatively similar oxide scales composed of an outer oxide layer of CoO and CoAlO phase on top of an AlO scale, following the inner oxide layers of CrO, TiO, and TiTaO, and internally oxidized AlO precipitate. The alloy forms a chromium-rich oxide scale as the Cr addition increased, and the concentration of Cr in the scale/alloy interface increases, promoting the growth of CrO, while CoAlO and CoO nucleation is inhibited. The results further indicate that Cr has a superior effect on improving the oxidation resistance of CoNi-based alloys and that a higher content of Cr can assist the formation of a continuous AlO, CrO, and TiTaO layers, which in turn hampers outer Co and Ni, and inward oxygen flux.
对Cr含量在1至5原子百分比范围内的多晶Co-30Ni-10Al-4W-4Ti-2Ta高温合金在900°C下的高温氧化行为进行了表征，以提供CoNi基高温合金合金设计的基准数据。所有三种合金的质量增加曲线均呈现抛物线型增长，与无Cr合金相比，添加5原子百分比的Cr足以使氧化速率降低两个数量级。此外，横截面研究结果表明，这三种合金形成了定性相似的氧化膜，由AlO膜之上的CoO和CoAlO相的外氧化层组成，其下方依次为CrO、TiO和TiTaO的内氧化层以及内部氧化的AlO析出物。随着Cr添加量的增加，合金形成富铬氧化膜，氧化膜/合金界面处的Cr浓度增加，促进了CrO的生长，同时抑制了CoAlO和CoO的形核。结果进一步表明，Cr对提高CoNi基合金的抗氧化性具有优异的作用，较高含量的Cr有助于形成连续的AlO、CrO和TiTaO层，进而阻碍外部的Co和Ni以及向内的氧通量。
