High-Temperature-Oxidation Behavior of Iron–Aluminide Diffusion Coatings

Abstract

Aluminide diffusion coatings were oxidized in air under atmospheric pressure under isothermal and cyclic conditions. The high-temperature efficiency of the pack-aluminized alloys was tested by comparing their oxidation behavior in the temperature range 800-1080°C. The k p values deduced from the parabolic plots of weight-gain curves showed that a-Al 2 O 3 composed the major phase of the oxide scale on samples oxidized at T > 1000°C. For lower temperatures, transient-alumina phases were observed. The aluminide materials also exhibited excellent resistance to cyclic oxidation at 1000°C. The second aim of this study was to dope the aluminide compounds obtained by a pack-cementation process with yttria, which was introduced by metal-organic chemical-vapor deposition (MOCVD). The beneficial effect of the reactive-element-oxide coating is strongly dependent on its mode of introduction, since the oxidation resistance is drastically increased when the Y 2 O 3 coating was applied prior to the aluminization process. When applied after the aluminization, the reactive element gave negative effects on the high-temperature oxidation behavior of the iron aluminides. The oxide morphologies, X-ray diffraction patterns and two-stage experiments helped to understand the oxide-scale-growth mechanisms.

High-Temperature Oxidation of Fe3Al and Fe3Al–Zr Intermetallics

“…Thus, RE additions as alloying elements in the alloys are of major importance to improve their oxidation resistance, leading to beneficial effect, called ''Reactive-Element Effect'' (REE). In a general way, the main REE for aluminaforming alloys is a huge improvement of the oxide-scale adherence to the metallic substrate [25][26][27][28][29][30][31][32][33][34][35]. This beneficial effect is also observed for iron aluminides, such as FeAl [6,8,9] and Fe 3 Al [36][37][38][39] intermetallics.…”

Water vapor effect on high-temperature oxidation behavior of Fe3Al intermetallics

“…This is particularly true for reactive-element addition, whose effect on the high-temperature corrosion of alumina-forming materials was largely studied [16][17][18][19][20][21][22][23][24][25][26][27].…”

The oxidation of Fe-30Al alloys in 1 atm of pure O2 at 973 K and 1173 K

“…Due to their practical importance, the oxidation mechanism of complex alloys has been investigated frequently during last few years. However, effect of temperature on oxidation behavior of multi-component alloys is very complex [1][2][3][4][5][6][7].…”