Solidification characteristics and segregation behavior of Ni-based superalloy K418 for auto turbocharger turbine
Solidification characteristics and segregation behavior of Ni-based superalloy K418 for auto turbocharger turbine
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DOI：
10.1016/j.jallcom.2013.03.241
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发表时间：
2013-09
影响因子：
6.2
通讯作者：
Zhao-xia Shi;Jian-Xin Dong;Mai-cang Zhang;Lei Zheng
中科院分区：
文献类型：
--
作者：
Zhao-xia Shi;Jian-Xin Dong;Mai-cang Zhang;Lei Zheng
采用DSC和等温凝固淬火技术研究了K418合金的凝固特性和偏析行为。通过实验测定了相变温度和固相分数随温度的变化，并用Thermo-Calc软件进行了对比计算。结果表明，凝固过程始于初生γ枝晶的形成，终止于γ/γ′共晶反应，并伴随MC碳化物和M（C，B）碳硼化物的形成。凝固过程中，枝晶间Nb、Ti、Zr、B、C和Mo元素明显富集，形成碳化物、碳硼化物和γ/γ′共晶。凝固后期固相分数缓慢增加的原因也是正偏析元素在枝晶间的强烈偏聚。在K418合金的情况下，平衡模型被证明是一个有价值的工具来预测凝固序列和相变温度。Scheil计算可用于研究凝固过程中的偏析行为。
The solidification characteristics and segregation behavior of K418 alloy were investigated by the DSC measurement and the isothermal solidification quenching process. Phase transformation temperatures, together with the solid fraction with temperature were measured by experiments and comparatively calculated by Thermo-Calc. It is demonstrated that the solidification begins with the formation of primary γ dendrite and terminates with the γ/γ′ eutectic reaction, being accompanied by the formation of MC carbide and M(C, B) carboboride. During the solidification, interdendritic region is significantly enriched with Nb, Ti, Zr, B, C and Mo, which results in the formation of carbide, carboboride and γ/γ′ eutectic. The slow increase of solid fraction at the final stage of solidification is also caused by the strong segregation of the positive segregation elements in interdendritic area. In the case of K418, equilibrium model is shown to be a valuable tool to predict the solidification sequence and phase transition temperatures. Scheil calculation can be used to investigate the segregation behavior during solidification.