Effect of grain size on the isothermal oxidation of superalloys

Abstract

The oxidation behavior of two different grain sizes of superalloys is discussed. The present paper focused on the isothermal oxidation of Fe-33Ni-19Cr alloy at temperatures of 700 °C exposed in dry air for 500 hours. Different grain size of alloy was made of solution annealing treatment at different temperatures, namely, 950 °C and 1200 °C for fine and coarse grain, respectively. The results showed that the average grain size increased with increase in solution annealing temperature that was significantly affecting the oxidation kinetic of the materials. Optical microscopy, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) were employed in this study to analyze the oxidation behavior of solution-annealed samples. Results indicate that fine grain samples recorded the slow oxidation rate as compared to coarse grain samples. The analysis indicates that the fine grain sample resulting in an enhanced Cr diffusivity to form Cr rich oxides. The fine grain solution-annealed sample is an effective approach, which possess a better oxidation resistance and reduced oxidation rate.