Heat treatment influence on the high temperature cyclic oxidation of Ni-based Fe-33Ni-19Cr alloy at 900°C

Ferum-nickel-chromium (Fe-Ni-Cr) alloy is a family of Ni-based alloy which is generally utilized in elevated temperature applications with excellent oxidation resistance properties. In this study, Fe-33Ni-19Cr alloy underwent a heat treatment procedure at 1000°C and 1100°C for 3 hours soaking time, and then rapidly cooled by water quench. The heat- treated alloys were then subjected to a cyclic oxidation test at 900°C for 150 cycles in air. The oxidized alloys were characterized in terms of weight change per surface area as a function of cycles and oxide scale behavior in plan and cross- sectional view using a scanning electron microscope outfitted with an energy dispersive x-ray spectrometer. It was found that the low heat treatment temperature, which is 1000°C, produced fine grain structure. Whereas, heat-treated alloy at 1100°C produced coarse grain structure. On the other hand, cyclic oxidation of both heat-treated oxidized alloys recorded a weight gain pattern. Various oxide phases were formed on the oxidized alloys surface, namely Cr-rich and Cr-Mn rich oxides. The surface morphology analysis exhibited an uninterrupted oxide layer established on the oxidized alloys surface, with fine grain heat-treated alloy forming a uniform oxide layer. However, oxide exfoliation has been recorded on coarse grain heat-treated alloys.