Abstract
Iron-chromium-aluminum (FeCrAl) alloys are being investigated as cladding material for urania nuclear fuel in light water power reactors. One extraordinary attribute of the FeCrAl alloys is their resistance to attack by air and steam up to their melting point. It was of interest to study the kinetics of oxidation of FeCrAl from 800°C to 1300°C in air and in steam to determine how the oxides evolve to provide protection to the alloys. The two investigated alloys were APMT (Fe-21Cr-5Al-3Mo) and C26M (Fe-12Cr-6Al-2Mo). Results show that both alloys had similar oxidation kinetics despite their different chemical compositions. For the testing times, the oxidation rate was higher in air than in steam at the higher temperatures (1100–1300°C) and higher in steam than in air at the lower temperatures (800–1100°C). In the lower temperature range, the surface oxide consisted of two layers, an internal layer rich in aluminum and an external layer containing Al, Cr, and Fe. In the higher temperature range, the oxide was a single layer of alumina (no Cr, no Fe, no Mo).
Highlights
Iron-chromium-aluminum (FeCrAl) alloys have been in existence for nearly 90 years
Some FeCrAl may contain 2% to 3% molybdenum (Mo) and smaller amounts of other elements such as yttrium (Y), zirconium (Zr), hafnium (Hf), and titanium (Ti). Their most outstanding feature is that FeCrAl alloys can be used for extended periods at 1200°C or higher temperatures because they develop on their surface a tenacious and adherent film of alumina (Al2O3), which protects the alloys from further degradation.[1]
FeCrAl alloys C26M and APMT (Table I) are highly resistant to attack by air or steam in the temperature range 800°C to 1300°C
Summary
Iron-chromium-aluminum (FeCrAl) alloys have been in existence for nearly 90 years. They are Febased ferritic materials (bcc structure) containing 12% to 21% Cr and 4% to 6% Al. Some FeCrAl may contain 2% to 3% molybdenum (Mo) and smaller amounts of other elements such as yttrium (Y), zirconium (Zr), hafnium (Hf), and titanium (Ti). Some FeCrAl may contain 2% to 3% molybdenum (Mo) and smaller amounts of other elements such as yttrium (Y), zirconium (Zr), hafnium (Hf), and titanium (Ti) Their most outstanding feature is that FeCrAl alloys can be used for extended periods at 1200°C or higher temperatures (both under isothermal and cyclic temperature conditions) because they develop on their surface a tenacious and adherent film of alumina (Al2O3), which protects the alloys from further degradation.[1] Current applications of FeCrAl include heating elements in furnaces, thermocouples, and even home toasters. APMT and FeCrAl ODS are powder metallurgy products,[5,8] and C26M and Aluchrom YHf are traditionally melted alloys.[6,9]
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