Characterization of Oxidation Kinetics and Oxide Scale Formation on Isothermal Oxidation of HR-120 Ni-based superalloy at 500ºC

Abstract

The HR-120 Ni-based superalloy underwent isothermal oxidation at 500°C in order to better understand the oxidation kinetics and the production of oxide scales. To create small and large grain structure, the HR-120 Ni-based superalloy was heat-treated at two distinct temperatures, 950ºC and 1100ºC. A 500°C for 500 h isothermal oxidation test was performed on the heat-treated alloy of the study examined the oxidation kinetics, oxide phase development and oxide surface morphology of alloy that had undergone isothermal oxidation. Plotting weight gain versus surface area allowed for the measurement of oxidation kinetics. The XRD method was used to examine the oxide phase. Surface morphology was investigated with SEM and EDX methods. A parabolic rate law was observed in the oxidation of both heat-treated alloys, suggesting a diffusion-controlled oxide growth mechanism. The alloy’s surface has developed many oxide phases as a result of exposures lasting 500 h. The oxidized samples’ surface morphology after 300 hours shows that overly large Nb-rich oxides are dispersed throughout the continuous oxide scale development. On coarse-grained heat-treated alloys, Nb-rich oxides produced that were abnormally big. This occurrence will initiate a crack that spreads around the oxide.