Cyclic Oxidation of Two FeCrAlRE Foils at 1100 °C - The Influence of the Concentration of Minor Alloying Elements on Scale Microstructure

Abstract

Two FeCrAlRE alloys, a commercial, 0C404, and a model alloy in the form of thin foils, with different Mn, Nb, Mo and Ti concentrations were subjected to cyclic oxidation in lab air at 1100°C. The oxidized samples were studied by gravimetry, Grazing-Incidence X-ray Diffraction (GI-XRD), Scanning Transmission Electron Microscopy (STEM), and Energy Dispersive X-ray (EDX) analysis. The two FeCrAl alloys exhibit different oxidation kinetics; however, both alloys have the same weight gain after 500 hours exposure. During the early stages the scale consists mainly of α-Al2O3 together with some oxide particles containing Mn, Al, Fe and Cr formed on the alloys. After 500 hours the 0C404 scale locally also consists of larger polycrystalline regions of Mn-Cr-Al spinel. In addition, Si-rich oxide, chromia and Al-Cr oxide could be observed at the metal/oxide interface.

Microstructural Investigation of the Initial Oxidation of the FeCrAlRE Alloy Kanthal AF in Dry and Wet O[sub 2] at 600 and 800°C

“…At high temperatures FeCrAl alloys, such as Kanthal AF, form a protective ␣-Al 2 O 3 scale that provides excellent oxidation resistance. While most of the research performed on these materials concerns temperatures above 1000°C, [1][2][3][4] they are often used at lower temperatures. Thus, FeCrAl materials are used as carrier materials for catalytic converters where the temperature is below 800°C.…”