High temperature oxidation mechanisms of grain refined Fe-25Al-1.5Ta(+TaC/+(Ta,Nb)C) iron aluminides at 700 °C in air

• Published in: Corrosion science 2022-04, Vol.198, p.110149, Article 110149
• Main Authors: Pütz, René Daniel, Zander, Daniela
• Format: Article
• Language: English
• Subjects: A. intermetallics (iron aluminides); Additives; Aluminum oxide; B. SEM; B. XRD; C. high temperature corrosion; C. internal oxidation; C. oxidation; Ferric oxide; High temperature; Iron aluminides; Laves phase; Niobium; Oxidation; Reaction kinetics; Tantalum
• ISSN: 0010-938X; 1879-0496
• DOI: 10.1016/j.corsci.2022.110149

The high temperature oxidation mechanisms of grain refined Fe-25Al-1.5Ta (at%) with TaC or (Ta,Nb)C additives were investigated at 700 °C in air for 503 h to study the influence of microstructural changes on the oxidation behaviour. While a thin and stable α-Al2O3 scale was formed at the Fe-Al matrix, additional phases were selectively oxidised leading to higher oxidation kinetics of Fe-25Al-1.5Ta with carbide additives. The selectively oxidised C14 (Fe,Al)2Ta Laves phase showed the formation of outer Fe2O3 and an inner (Al,Ta)-rich oxide, while Al-rich oxides were found along the (Al,Ta)-rich oxide/Fe-Al phase boundary and locally below Fe2O3. •The grain size of Fe-25Al-1.5Ta was reduced by 2.4 wt% TaC/(Ta,Nb)C.•A thin and stable α-Al2O3 scale was formed at the Fe-Al matrix with the same thickness for all iron aluminides.•The additional phases (Fe,Al)2Ta and carbides were selectively oxidised at the surface region.•The mass gain of iron aluminides with carbide additives increased due to a higher cumulative fraction of phases.•(Fe,Al)2Ta was formed below the oxide layer that was not selectively oxidised.