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Examination of the Oxidation and Metal–Oxide Layer Interface of a Cr–Nb–Ta–V–W High Entropy Alloy at Elevated Temperatures

The authors report on the evaluation of the oxide scale and the interface microstructure of a Cr–Nb–Ta–V–W refractory high entropy alloy (HEA) at elevated temperatures. The Cr–Nb–Ta–V–W HEA is oxidized at 700 and 800 °C in lab air and the substrate/oxide interface is investigated. Combined in situ X...

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Bibliographic Details
Published in:Advanced engineering materials 2021-08, Vol.23 (8), p.n/a
Main Authors: Romero, Rebecca, Makeswaran, Nanthakishore, Naraparaju, Ravisankar, Ramana, Chintalapalle V.
Format: Article
Language:English
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Summary:The authors report on the evaluation of the oxide scale and the interface microstructure of a Cr–Nb–Ta–V–W refractory high entropy alloy (HEA) at elevated temperatures. The Cr–Nb–Ta–V–W HEA is oxidized at 700 and 800 °C in lab air and the substrate/oxide interface is investigated. Combined in situ X‐ray diffraction (XRD) coupled with ex situ scanning electron microscopy (SEM) and energy dispersive X‐ray spectrometry (EDS) analyses characterize the oxide scale and confirm the phases present in the substrate which have been previously identified in this alloy. The microstructure near the interface is studied for an indication of selective oxidation of this alloy. Cracking and porosity are found along the interface layer which grows directionally outward. Two main oxides are identified: a W‐based oxide with a needle‐like structure and a Cr oxide containing Ta that has a granular structure, primarily found in clusters. The oxide layers are porous, and no dense protective oxide is identified. It is found that when the temperature is increased to 800 °C, the oxide layer exhibits an increase in thickness. In situ XRD indicates that V is the first element to oxidize. The interface between the substrate and oxide layer of a CrNbTaWV high entropy alloy is studied. The interface of samples that has been oxidized at 700 and 800 °C was examined for the oxidation behavior of constituent elements and to further understand the morphology and oxide composition. Two main oxides are identified, a W‐rich oxide and Cr‐rich oxide containing Ta.
ISSN:1438-1656
1527-2648
DOI:10.1002/adem.202100164