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Possibility of metallic cobalt formation in the oxide scale during high-temperature oxidation of Co-27Cr-6Mo alloy in air
Author(s)
Ponpo, Phisan
Nilsonthi, Thanasak
Chandra-Ambhorn, Somrerk
Date Issued
January 1, 2023
Type
Article
Abstract
Co-based alloys are known to be high oxidation-resistant material and used in several high temperature applications. During high temperature oxidation, duplex oxides containing Co and Cr were formed. It was thermodynamically elucidated that when the growing scale was thick enough, the partial pressure of O2 in the scale dropped. Then, the reduction of CoO occurred for promoting O2 which was responsible for Cr2O3 production. This work experimentally proved this point by in situ char-acterising Co-27Cr-6Mo at high temperatures in air by X-ray diffractometer in a grazing incident mode and metallic Co was confirmed to be formed by the reduction of CoO consistent with the image taken and analysed by field emission scanning electron microscope, energy-dispersive X-ray, and electron backscatter diffraction. Furthermore, the change in lattice parameter and the phase transition were observed when the temperature was altered.
Citation
High Temperature Materials and Processes, 42(1), 2023