Oxidation Behavior of Fe-Al, Fe-Si and Fe-Al-Si Intermetallics.

Pavel Novák,Kateřina Nová

doi:10.3390/ma12111748

Abstract

Iron aluminides are still deeply investigated materials for their use in power plants, automotive and chemical industry, and other sectors. This paper shows that it is possible to strongly improve their oxidation behavior by the addition of silicon. The description of the synergic effect of aluminum and silicon on the oxidation behavior of Fe–Al–Si alloys at 800 °C in air is presented. The oxidation rate, microstructure, phase, and chemical composition of these ternary alloys are compared with the binary Fe–Al and Fe–Si alloys. Results showed that the oxidation of Fe–Al–Si ternary alloys provides an oxide layer based on aluminum oxide with a low concentration of iron and silicon. Below this oxide layer, there is a layer of silicides formed as a result of depletion by aluminum, which forms a secondary oxidation protection.

Highlights

Iron aluminides have attracted considerable attention since the 1950s due to their very good resistance against oxidation and sulfidation atmosphere [1]
Fe–Al and Fe–Al–Si alloys tend to form the oxide layer based on aluminum oxide due to a the oxidation behavior of all tested alloys, we can formulate the following statements
Fe–Al and Fe–Al–Si alloys tend to form the oxide layer based on aluminum oxide due to a high cubic γ-Al2 O3, which is known to have a lower protective effect than α-Al2 O3, which forms at higher thermodynamic stability of this oxide (Table 5)

Summary

Introduction

Iron aluminides have attracted considerable attention since the 1950s due to their very good resistance against oxidation and sulfidation atmosphere [1]. Fe–Al–C system had been developed, having been based on cast iron with the addition of aluminum [1]. These alloys were composed of B2 iron aluminide (FeAl) matrix and aluminum carbide particles [1]. The aluminum carbides can exist in two forms—sole Al4 C3 carbide and mixed Fe3 AlC carbide with perovskite structure [2,3]. The existence of Al4 C3 carbide is the biggest problem with this group of materials, because it can form methane when in contact with acidic environments or water vapor at high temperatures [4]. Nowadays the iron aluminide materials without carbon are of high interest. There are numerous studies on the effect of particular alloying elements, such as Cr, Nb and

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