Influence of Grain Size on Isothermal Oxidation of Fe–33Ni–19Cr Alloy

Abstract

This research study describes the influence of grain size on isothermal oxidation of Fe–33Ni–19Cr alloy. The Fe–33Ni–19Cr alloy was undergone heat treatment of three different temperatures, namely 1000, 1100, and 1200 °C for 2 h of soaking time followed by water quench to vary the grain size of alloy. This alloy was ground by using several grit of sandpaper as well as weighed by using analytical balance and measured by using vernier calipers before oxidation test. The heat-treated Fe–33Ni–19Cr alloy was isothermally oxidized at 800 °C for 150 h. The characterization of oxidized samples was carried out using optical microscope, scanning electron microscope equipped with energy dispersive X-ray and X-ray diffraction. The result shows that increasing the heat treatment temperature will increase the average grain size. Fine grain size promotes the higher boundary area which acts as an ion diffusion path across the metal–gas interface. Heat-treated sample at 1000 °C with fine grain structure shows minimum weight gain and lower oxidation rate compared to alloys heat treated at 1100 and 1200 °C. Alloy heat treated at 1000 °C shows continuous oxide layer formed on the surface, while alloy heat treated at 1200 °C indicates oxide spallation. Besides, phase analysis shows that the oxidized sample formed several oxide phases.