Oxidation behaviour of a novel refractory high entropy alloy at elevated temperatures

• Published in: Intermetallics Vol. 119; p. 106711
• Main Authors: Lo, Kai-Chi, Murakami, Hideyuki, Yeh, Jien-Wei, Yeh, An-Chou
• Format: Journal Article
• Language: English
• Published: Barking Elsevier Ltd 01.04.2020; Elsevier BV
• Subjects: Aluminum oxide; Behavior; Chromium oxides; Corrosion; High entropy alloys; High temperature; Microstructure; Mullite; Nickel base alloys; Oxidation; Oxidation resistance; Reaction kinetics; Segregation; Superalloys; Surface properties; Surface properties; High–entropy alloys; Oxidation; Corrosion; Microstructure; Segregation
• ISSN: 0966-9795; 1879-0216
• DOI: 10.1016/j.intermet.2020.106711

The refractory high entropy alloy (RHEA) has shown great potentials for high temperature applications beyond modern Ni-based superalloy. However, its oxidation behaviours are rarely reported and understood. In this work, the oxidation behaviours of a novel RHEA “NV1”, Cr-17.6Al-20.3Mo-15.2Nb-2.9Si-13.4Ta-5.4Ti (in at%), were examined at 1200, 1300, and 1400 °C up to 100 h. At 1200 °C, the oxidation kinetics curve yielded toward parabolic behaviour owing to the formation of a rutile-type complex oxide layer with Al2O3 and Cr2O3 dispersions; breakaway oxidation contributed by Cr2O3 evaporation occurred at 1300 °C; a single power-law behaviour governed the oxidation kinetics curve at 1400 °C, and mullite was identified within the oxide layer. This work provides guidelines for understanding the oxidation mechanisms and improving oxidation resistance of RHEA at elevated temperature. •A new refractory high entropy alloy were oxidised up to 1400 °C for 100 h.•Microstructural evolution strongly affected the oxidation of the studied alloy.•(Al, Cr)(Nb, Ta)O4 external oxide layer was protective against oxidation.•Strong Ti-rich nitride presence was observed deep beneath the oxidised regions.