Oxide scale growth on Fe-40Ni-24Cr alloy at high temperature oxidation

Abstract

Fe-40Ni-24Cr alloy is a Ni-based alloy used at high temperature application. In this study, Fe-40Ni-24Cr alloy had undergo a solution treatment at two different temperatures, namely 1050° and 1150°, for 3 hours soaking times followed by water quench. A solution-treated Fe-40Ni- 24Cr alloy was experienced a high temperature isothermal oxidation test at 500° for 500 hours exposures duration. The growth of oxide scale was characterized in terms of oxidation kinetics and surface morphology using field emission scanning electron microscope equipped with energy dispersive x-ray spectroscopy. The oxidation kinetics of all samples shows an increasing weight gain pattern as the exposure durations increases. The oxidation kinetics was obeyed a parabolic rate law, indicating the oxide growth rate was followed diffusion-controlled mechanism. The surface morphology of oxidized solution-treated Fe-40Ni-24Cr alloy displayed a formation of continuous oxide scale with evidence of overgrown Nb-rich oxide particles distributed along the oxidized samples surface. Oxidized Fe- 40Ni-24Cr alloy which undergo solution treatment at 1150° exhibited the formation of oxide spallation. The spallation has a tendency to occur around the area of overgrown Nb-rich oxide particles.