Activity coefficients of NiO and CoO in CaO–Al₂O₃–SiO₂ slag and their application to the recycling of Ni–Co–Fe-based end-of-life superalloys via remelting

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• 作者：Xin Lu ; Takahiro Miki ; Tetsuya Nagasaka
• 关键词：recycling ; nickel ; cobalt ; end ; of ; life ; superalloys ; activity coefficients ; remelting ; slag
• 刊名：International Journal of Minerals, Metallurgy, and Materials
• 出版年：2017
• 出版时间：January 2017
• 年：2017
• 卷：24
• 期：1
• 页码：25-36
• 全文大小：
• 刊物类别：Chemistry and Materials Science
• 刊物主题：Materials Science, general; Metallic Materials; Characterization and Evaluation of Materials; Ceramics, Glass, Composites, Natural Materials; Surfaces and Interfaces, Thin Films; Tribology, Corrosion
• 出版者：University of Science and Technology Beijing
• ISSN：1869-103X
• 卷排序：24

文摘

To design optimal pyrometallurgical processes for nickel and cobalt recycling, and more particularly for the end-of-life process of Ni–Co–Fe-based end-of-life (EoL) superalloys, knowledge of their activity coefficients in slags is essential. In this study, the activity coefficients of NiO and CoO in CaO–Al₂O₃–SiO₂ slag, a candidate slag used for the EoL superalloy remelting process, were measured using gas/slag/metal equilibrium experiments. These activity coefficients were then used to consider the recycling efficiency of nickel and cobalt by remelting EoL superalloys using CaO–Al₂O₃–SiO₂ slag. The activity coefficients of NiO and CoO in CaO–Al₂O₃–SiO₂ slag both show a positive deviation from Raoult’s law, with values that vary from 1 to 5 depending on the change in basicity. The activity coefficients of NiO and CoO peak in the slag with a composition near B = (%CaO)/(%SiO₂) = 1, where B is the basicity. We observed that controlling the slag composition at approximately B = 1 effectively reduces the cobalt and nickel oxidation losses and promotes the oxidation removal of iron during the remelting process of EoL superalloys.