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Advances in Materials Research Volume 7, Number 1, March 2018 , pages 17-28 DOI: https://doi.org/10.12989/amr.2018.7.1.017 |
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Microstructures and hardness of model niobium-based chromium-rich cast alloys |
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Patrice Berthod and Mélissa Ritouet-Léglise
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| Abstract | ||
| Niobium is a candidate base for new alloys devoted to applications at especially elevated temperatures. Elaborating and shaping niobium-based alloys by conventional foundry may lead to mechanically interesting microstructures. In this work a series of charges constituted of pure elements were subjected to high frequency induction melting in cold crucible to try obtaining cast highly refractory Nb-xCr and Nb-xCr-0.4 wt.%C alloys (x=27, 34 and 37 wt.%). Melting and solidification were successfully achieved. The as-cast microstructures of the obtained alloys were characterized by electron microscopy and X-ray diffraction and their hardness were specified by Vickers macro-indentation. The obtained as-cast microstructures are composed of a body centered cubic (bcc) niobium dendritic matrix and of an interdendritic eutectic compound involving the bcc Nb phase and a NbCr2 Laves phase. The obtained alloys are hard to cut and particularly brittle at room temperature. Hardness is of a high level (higher than 600Hv) and is directly driven by the chromium content or the amount of {bcc Nb – NbCr2} eutectic compound. Adding 0.4 wt.% of carbon did not lead to carbides but tends to increase hardness. | ||
| Key Words | ||
| niobium-based alloys; chromium; carbon; foundry; as-cast microstructures; hardness | ||
| Address | ||
| Patrice Berthod: 1. Institut Jean Lamour (UMR CNRS 7198), Campus Artem, University of Lorraine, Postal Box 50840, F-54011 Nancy Cedex, France 2. Faculty of Sciences and Technologies, Campus Victor Grignard, University of Lorraine, Postal Box 70239, F-54506 Vandoeuvre-lès-Nancy Cedex, France Mélissa Ritouet-Léglise:Institut Jean Lamour (UMR CNRS 7198), Campus Artem, University of Lorraine, Postal Box 50840, F-54011 Nancy Cedex, France | ||
