Mechanistic insights into the oxidation behavior of Ni alloys in high-temperature CO2. (15th August 2017)

• Record Type: Journal Article
• Authors: Oleksak, Richard P.; Baltrus, John P.; Nakano, Jinichiro; Nakano, Anna; Holcomb, Gordon R.; Doğan, Ömer N.
• Is Part Of: Corrosion science. Volume 125(2017)
• Page Start: 77
• Page End: 86
• Publication Date: 2017-08-15
• Subjects: A. Nickel -- B. TEM -- C. Oxidation -- C. Selective oxidation -- C. High temperature corrosion -- Carbon dioxide; Corrosion and anti-corrosives -- Periodicals; 620.11223
• DOI: 10.1016/j.corsci.2017.06.005
• Languages: English
• ISSNs: 0010-938X

Abstract

Highlights: The oxidation behavior of a Ni alloy in high-temperature CO2 is evaluated in detail. CO2 molecules play little role during the oxidation process. O2 impurities control oxidation in metallic regions of the alloy. Oxidation of metal carbides is enhanced in the presence of CO2 . Cr vacancies lead to significant interfacial voids during early stages of oxidation. Abstract: We present results of a Ni superalloy oxidized for short times in high purity CO2 and similarly in Ar containing ≤ 1 ppb O2 . A detailed analysis of the oxidized surfaces reveals striking similarities for the two exposure environments, suggesting O2 impurities control the oxidation process in high-temperature CO2 . Selective oxidation results in Cr-rich oxide layers grown by outward diffusion, while Cr vacancies left in the metal contribute to significant void formation at the oxide/metal interface. Unlike for most of the alloy surface, the oxidation behavior of secondary phase metal carbides is considerably different in the two environments.