Effect of Nb on Oxide Formation by Isothermal Oxidation of Solution Treated Fe-40Ni-24Cr Ni-Based Alloy

The study on solution treated Fe-40Ni-24Cr Ni-based alloy on the isothermal oxidation has been investigated. The solution treatment process has been done at two temperatures, which are 1100°C and 1200°C. The alloys were soaking for 3 hours, followed by rapid cooling using water cooled. The solution treated Fe-40Ni-24Cr Ni-based alloy were experienced an isothermal oxidation test at 700°C for 500 hours exposure time. The effect of Nb alloying element on the oxide growth behavior has been characterized in termed of plan and cross sectional view using scanning electron microscope with energy dispersive x-ray spectrometer. As a results, good protective oxide scale has formed on the fine grain solution treated sample with homogeneous and dense oxide structure. On the other hand, coarse grain solution treated sample demonstrated an oxide exfoliation after 500 hours exposure around the overgrown Nb-rich oxide precipitate area, hence indicating poor oxidation protection.