Improvement in oxidation behavior of Al0.2Co1.5CrFeNi1.5Ti0.3 high-entropy superalloys by minor Nb addition

• Published in: Journal of alloys and compounds Vol. 825; p. 153983
• Main Authors: Yang, Jun-Jie, Kuo, Chia-Ming, Lin, Po-Ting, Liu, Hung-Chih, Huang, Cheng-Yao, Yen, Hung-Wei, Tsai, Che-Wei
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 05.06.2020; Elsevier BV
• Subjects: Backscattering; Base metal; Electron imaging; Electron probes; Entropy; High temperature; High-entropy alloy; High-entropy superalloy; Mechanical properties; Minor addition; Nickel base alloys; Niobium; Oxidation; Oxidation resistance; Precipitates; Superalloys; Thermogravimetry; Minor addition; Oxidation; Niobium; High-entropy superalloy; High-entropy alloy
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2020.153983

High-entropy superalloys (HESAs) can replace commercial Ni-based superalloys. For high-temperature applications, the oxidation resistance of HESAs must be considered. Herein, the oxidation mechanism of HESA with sufficient minor Nb addition was conducted at 900 °C under atmosphere. With 0.9 at% Nb added in the base metal, oxidation resistance was significantly improved, which was confirmed by a furnace test and thermogravimetry. The isothermal oxidation resistance was enhanced by approximately 66%, owing to the presence of the Nb-rich layer. This improvement was observed and analyzed by backscattering electron images through scanning electron microscopy and wavelength dispersive spectroscopy with a field-emission electron probe microanalyzer. The mechanism of oxide formation was elucidated by X-ray diffraction for various exposure time durations. With Nb minor addition, the microstructures of the present alloy were found to be composed of γ matrix and γ′ precipitates and the mechanical properties were slightly higher than those without Nb.