The oxidation of Co–Y binary alloys at 600–800°C in air

• Published in: Corrosion science Vol. 41; no. 9; pp. 1731 - 1742
• Main Authors: Zeng, C.L., Rizzo, F.C., Wu, W.T., Monteiro, M.J.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01-08-1999; Elsevier Science
• Subjects: Applied sciences; Corrosion; Corrosion tests; Exact sciences and technology; Metals. Metallurgy; Oxidation; Co; Y; Oxidation; Corrosion rate; Air; Hot corrosion; Experimental study; Cobalt; X ray diffraction; Corrosion product; Cobalt base alloys; Oxide scale; Corrosion; Transition metal alloy; Corrosion test; Gas corrosion; Yttrium alloy; Microstructure; Binary alloy
• ISSN: 0010-938X; 1879-0496
• DOI: 10.1016/S0010-938X(99)00011-6

The oxidation of pure Co and two Co–Y alloys containing 2
at.% and 5
at.% Y has been studied at 600–800°C in air. The oxidation of pure cobalt at all temperatures followed the parabolic rate law. The oxidation of the two alloys approximately followed the parabolic rate law at 800°C, but was closer to cubic behavior at 600 and 700°C except Co–5Y at 600°C, which deviated from the cubic and parabolic rate law. The corrosion of both alloys at the three temperatures produced an external scale containing Co oxides (Co
3O
4, CoO) and Y
2O
3 and an internal oxidation region where Co
17Y
2 was converted into Co and Y
2O
3. The distribution of Y
2O
3 closely followed that of the intermetallic compound (Co
17Y
2) in the original alloy. The corrosion mechanism of the alloys is examined.