ニッケル基超合金溶湯からの蒸発による合金組成の変化

概要

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Change in chemical compositions by evaporation from molten Ni-base superalloys was studied. Elements evaporating from molten metals were Cr, Co and Ni. Among these elements, evaporation rate of Cr was remarkably high. Cr content in alloys decreased in proportion to holding temperature and time. Comparing conventional casting alloys with single crystal casting alloys, evaporation rate of Cr in single crystal casting alloys was smaller than that of conventional casting alloys. This is due to that alumina film was more easily formed on the surface of single crystal molten alloys than on the surface of conventional casting molten alloys. There was a tendency that elements other than Cr increased according to the decrease of Cr content. This apparent change in compositions is well explained by decrease of Cr content. In order to avoid evaporation of Cr, making the molten metal surface as small as possible and making the pressure at above 4×10-1Pa are effective.
Japan Foundry Engineering Societyの論文