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<p>To enhance the high-temperature oxidation resistance and mechanical properties of a second-generation nickel-based superalloy, various concentrations of lanthanum (La) ranging from 5.0×10<sup>−5</sup>wt.% to 3.4×10<sup>−4</sup>wt.% are added to the alloy. The microstructure of the nickel-based single crystal superalloy with trace of La was examined by means of SEM, EDS and TEM. Results show the addition of La decreases the segregation of elements and increases the amount of γ/γ′ eutectics of the as-cast alloy, and in the interdendritic region, the growth of eutectics is accompanied by the growth of strip clusters composed of Ni<sub>5</sub>La and Ni<sub>3</sub>Ta. As the La content in the alloy increases, the proportion of Ni<sub>5</sub>La in the cluster increases. After heat treatment, incipient melting occurs in the cluster regions, leading to an increase in microporosity compared to the original as-cast samples. Furthermore, the heat treatment alters the shape of the clusters from a strip morphology to an elliptical one, and it changes their composition from Ni<sub>5</sub>La and Ni<sub>3</sub>Ta to a combination of Ni<sub>5</sub>La, Ni<sub>3</sub>Ta, and MC carbides.</p>

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Effect of lanthanum on microstructure of a nickel-based single crystal superalloy

  • 期刊论文

  • 发表日期：

    2025年1月7日

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  • Hong Gao,
  • Kai Guan,
  • Ren-jie Cui,
  • Jian-chao Qin,
  • Zi-han Zhao,
  • Zhao-hui Huang

摘要

To enhance the high-temperature oxidation resistance and mechanical properties of a second-generation nickel-based superalloy, various concentrations of lanthanum (La) ranging from 5.0×10−5wt.% to 3.4×10−4wt.% are added to the alloy. The microstructure of the nickel-based single crystal superalloy with trace of La was examined by means of SEM, EDS and TEM. Results show the addition of La decreases the segregation of elements and increases the amount of γ/γ′ eutectics of the as-cast alloy, and in the interdendritic region, the growth of eutectics is accompanied by the growth of strip clusters composed of Ni5La and Ni3Ta. As the La content in the alloy increases, the proportion of Ni5La in the cluster increases. After heat treatment, incipient melting occurs in the cluster regions, leading to an increase in microporosity compared to the original as-cast samples. Furthermore, the heat treatment alters the shape of the clusters from a strip morphology to an elliptical one, and it changes their composition from Ni5La and Ni3Ta to a combination of Ni5La, Ni3Ta, and MC carbides.