Influence of heat treatment on the isothermal oxidation of Fe-40Ni-24Cr alloy

Abstract

The isothermal oxidation behaviour of two different heat treated of Fe-40Ni-24Cr alloy was studied in this work. The present paper focuses on the isothermal oxidation behaviour at 700°C. Heat treatment at 2 different temperatures, namely 1000°C and 1200°C was applied to Fe-40Ni-24Cr alloy to alter the grain size of the samples. The heat treatment results showed that the average grain size increased with increase in heat treatment temperature. Optical microscopy, Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray Spectroscopy (EDS) and X-Ray Diffraction (XRD) were employed in this study to analyse the oxidation behaviour of heat treated samples. The heat treated samples were subjected to oxidation experiment under isothermal conditions for 500 hours. The oxide scale formed during oxidation were generally complex consists of several oxide phases. The samples morphologies of oxidized samples were influenced by the alloy structure and expose conditions. The kinetics of oxidation followed the parabolic law which represent diffusion controlled oxide growth rate. Results indicate that the fine grain size of alloy heat treated at 1000°C possess a better oxidation resistance and lowered the oxidation rate.