Oxidation iron aluminide

Since a general understanding is that the strength of iron aluminides is lower than that of other aluminides of interest, the relevant research is relatively few. However, an excellent resistance to oxidation and corrosion was reported for iron aluminide of p-Fe-A1 type by Okada et al. [66] together with their mechanical properties at high temperatures. 

It is more difficult to establish a protective A1203 scale at lower temperatures than at higher temperatures, particularly on alloys of relatively low aluminium concentrations thus, an iron aluminide containing 8 wt% Al formed more extensive sulphides at 500°C than at 700°C, although a protective oxide scale prevented significant sulphidation of an alloy containing 12 wt% Al at either temperature. 

Properties such as good resistance to oxidation and corrosion (in particular sulfidation), low density (Fe3Al 6.5 g cm FeAl 5.6 g cm" ), inexpensive raw materials, and low content of strategic elements have driven the development of iron aluminides. 

The maximum temperature at which iron aluminides have sufficient strength for structural application (600-650 C) is significantly lower than temperatures at which they have maximum resistance to corrosion (>900 °C). One approach to boosting the high-temperature mechanical properties has been the development of oxide dispersion-... 

Given that Fe-Al intermetallics were among the earliest intermetallics investigated, a historical perspective of Fe-Al alloy development will be presented. This is followed by a discussion of the oxidation behavior of Fe3Al and FeAl in air. Because of interest in their use in complex, corrosive environments, a detailed discussion of the oxidation behavior of iron aluminides in intermediate temperature (<800°C) environments containing species such as sulfur, chlorine, and carbon will also be presented. 

The high-temperature oxidation behavior of Fc3Al-based iron aluminides has been well documented in recent years (Pint et al., 1999 c Tortorelli and Natesan, 1999). The critical Al concentration for exclusive AI2O3 formation is reduced by addition of Cr (Tortorelli and DeVan, 1992) or increased by addition of Ni (Tomaszewicz and... 

Corrosion of iron aluminides by a highly aggressive, oxidizing molten salt used in chemical air separation processes (NaN03-KN03-Na202) at 650 °C has been shown to proceed by oxidation and slow release of an Al-rich product layer into the salt. Alloys richer in Al were significant-... 

Klower J. High Temperature Corrosion Behaviourof Iron Aluminides and Iron- Aluminium-Chromium Alloys In Grabke HJ, Schiitze M, editors. Oxidation of intermetaUics. Weinheim - Germany Wiley-VCH Verlag GmbH 1997. p. 203-20. 

Mas] Masahashi, N., Watanabe, S., Hanada, Sh., Microstmcture and Oxidation Behaviour of Low Pressure Plasma Sprayed Iron Aluminides , ISU Int., 41(9), 1010-1017 (2001) (Crys. Stmcture, Experimental, Meehan. Prop., 16)... 

Lee and Lin (1999) studied the oxidation, mixed oxidation-sulphidation and hot corrosion of ductile iron aluminide Fe3Al with Cr addition at temperatures of 605-800°C. They observed that hot corrosion of iron aluminide was significantly more severe than oxidation and mixed oxidation-sulphidation. According to Lee and Lin, this can be attributed to the formation of aluminium sulphide at the metal-salt interface as a result of high sulphur potential in the molten salt at the oxide-metal interface. 

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