Corrosion iron aluminides

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. 

High Temperature Corrosion Behaviour of Iron Aluminides and Iron-Aluminium Chromium Alloys... 

The high temperature corrosion behaviour of different iron aluminides and iron-aluminium-chromium alloys containing 6-17 wt% aluminium, 2-10 wt% chromium and additions of mischmetal has been investigated in both air and hot process gases. 

The present monograph was first written as a chapter for Volume 8 of the series Materials Sdence and Technology A Comprehensive Treatment , edited by Robert W. Cahn, Peter Haasen, and Edward J. Kramer (Volume Editor Dr. Karl Heinz Matucha). Its aim is to give an overview of intermetallics, which is both detailed and comprehensive and which includes the fundamentals as well as applications. The result is an extended, critical review of the whole field of intermetallics with an emphasis on those intermetallic phases which have already been applied as functional or structural materials or which are currently the subject of materials developments. A historical introduction and a discussion of the relationship between atomic bonding, crystal structure, phase stability and properties is followed by a discussion of the major classes of intermetallics. The titanium aluminides, nickel aluminides, iron aluminides, copper phases, A15 phases. Laves phases, beryllides, rare earth phases, and siliddes are reviewed. In particular, the crystal structures, phase diagrams, and physical properties as well as the mechanical and corrosion behavior are treated. The state of developments as well as prospects and problems are discussed in view of present and future applications. The publisher has decided to publish the review as a separate monograph in order to make it accessible to a wider audience. 

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. 

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-... 

P. (1997), Mater. Sci. Eng. A 234-236, 22-29. Bakker, W. T. (1998), Corrosion of Iron Aluminides in HCl-Containing Coal Gasification Environments, Paper No. 185, Corrosion/98. Houston, TX NACE International. 

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. 

Esp] Espinosa-Medina, M.A., Casales, M., Martinez-Villafane, A., Porcayo-Calderon, J., Martinez, L., Gonzalez-Rodriguez, J.G., Hot Corrosion of Atomized Iron Aluminides Doped Wifli Boron and Reinforced With Alumina , Mater. Sci. Eng. A, A300(l-2), 183-189 (2001) (Experimental, Meehan. Prop., Morphology, 18)... 

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. 

Iron aluminides, including Fc3 A1 and FeAl, are of interest for high-temperature stmctural applications since they have relatively high melting points, excellent oxidation, carburisation, sulfidation, and hot corrosion resistance, relatively low density and low material cost. The major advantages that can be derived from the use of iron aluminides include the following [215,216] ... 

Tortorelli P F and Natesan K (1998), Critical Factors Affecting the High-Temperature Corrosion Performance of Iron Aluminides, Mater Sci Eng, A258, 115-125. 

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