Oxidation Behaviour of Fe-28Al-5Si at.% Alloyed with Ti and Mo

Abstract

AbstractThe high-temperature oxidation behaviour of Fe-28Al-5Si, Fe-28Al-5Si-2Mo and Fe-28Al-5Si-2Ti (in at.%) was investigated. Cyclic oxidation tests of iron aluminides were performed at 900°C and 1100°C. The oxidation kinetics and oxidation behaviour (by measuring of total weight gain, etc.) were described. The structure of the alloys’ surfaces after oxidation, as well as the composition and morphology of oxide layers, was analysed by optical microscopy, scanning electron microscopy, SEM–EDS and X-ray diffraction. The beneficial effect of alloying with titanium or molybdenum on the oxidation resistance of Fe-Al-Si-based alloys was observed at temperatures of 900°C and 1100°C. Titanium and molybdenum suppress the formation of eutectic regions of the secondary phase in the structure, which preferentially oxidize. Therefore, a thin and compact alumina layer (only minor amounts of iron oxides and ZrO2) formed on the surface of Fe-28Al-5Si-2Mo and Fe-28Al-5Si-2Ti at 900°C. These alloys maintain low weight gains even at a temperature of 1100°C. On the other hand, alloy Fe-28Al-5Si contains a high number of eutectics-like areas, which causes ingress of the oxidation (selective oxidation of eutectic areas) and breakaway oxidation is observed at 900°C and 1100°C, respectively.