Oxidation Kinetics of Fe-Ni-Cr Alloy at 900 °C

Abstract

The study of isothermal oxidation of Fe-Ni-Cr alloy was done at 900 °C for 500 hours. The effect of oxidation kinetics and oxide growth behavior on Fe-Ni-Cr alloy were investigated on heat-treated Fe-Ni-Cr alloy to understand the oxidation mechanism on different grain size of alloy. The grain size of Fe-Ni-Cr alloy was varying through heat treatment process at three different temperatures, namely 1000 °C, 1100 °C and 1200 °C for 3 hours soaking time followed by water quench. The heat-treated Fe-Ni-Cr alloy was experienced discontinuous isothermal oxidation test at 900 °C up to 500 hours exposure. The oxidation kinetics plot was calculated based on the weight change per surface area over time. The oxide surface morphology was characterized by using scanning electron microscope (SEM) equipped with energy dispersive x-ray (EDX) spectrometer. The heat treatment process recorded an increasing grain size alloy as the heat treatment temperature increase. 8H10 sample indicate the fine grain size, whereas 8H12 sample indicate the coarse grain size. The oxidation kinetics of all samples exhibit the weight gain pattern with fine grain 8H10 sample recorded the lowest weight gain compared to 8H11 and 8H12 samples. All samples were obeyed parabolic rate law indicating the oxide growth rate followed a diffusion-controlled mechanism. The oxide surface morphology of 8H10 sample displayed a continuous oxide scales with formation of grain boundary oxide along the grain boundary area. Similar oxide structure formed on 8H11 and 8H12 samples, except for the formation of crack on the grain boundary oxide on both samples. In addition, 8H12 sample also formed a porous oxide structure.

Role of Mn Alloying Element on the Oxide Growth Behavior of 800H Nickel-Based Alloy at 900°C

“…The maximum weight change per area is 0.9443 mgcm -2 at 150 cycles exposure. This data is comparable with the weight gain of similar alloy expose under isothermal oxidation at the same temperature of 900 °C [13]. The increasing weight change trend shows that the oxide thickness was also increase to developed a protective oxide layer on the surface.…”

Oxidation Kinetic and Oxide Scale Morphology of Fe-33Ni-19Cr Ni-Based Superalloy

“…The fine grain size of HT1000 sample exhibited little weight gain compared to coarse grain size sample of HT1100. Low weight gain was recorded by HT1000 sample is due to the higher ion diffusion rate that formed rapid continuous initial oxide layer which enhance the protection behaviour, hence reduced the oxidation rate [6]. Based on the kinetics of oxidation curve, no indication of weight loss was attained, and hence no oxide mitigation has happened.…”

“…4 (b) show a close up of FESEM image on the grain boundary oxide. The formation of grain boundary oxide was basically resulted from the rapid outward ion diffusion through grain boundary path which produces a notch feature and a network-like structure under a plan view [6,13]. The fine grain size provides high grain boundary area that could enhance the formation of initial oxide structures, hence established the development of protective oxide scale on the alloy surface.…”

“…High diffusion rate will accelerate the formation of rapid initial oxide layer. Initial oxide formation is essential to established a dense and adherence oxide structure, hence provide protection behavior [6]. The heat treatment process at different temperatures may alter the grain size of the alloy, varies from coarse to fine grain structure [7,8].…”

The Influence of Al and Nb on the Low Oxygen Pressure Pre-Oxidation Behavior of Fe-35Ni-20Cr-xAl-yNb Alloys at 1000 °C

“…Its high-temperature and high-carbon working environment places strict requirements on the oxidation resistance and carburization resistance requirements for equipment materials [1,2]. Stainless steel and Fe-Ni-Cr centrifugal casting alloys are commonly used, with their oxidation resistance effectively enhanced by the rapid formation of a surface Cr 2 O 3 oxygen barrier layer [3], which obstructs the flow of oxygen into the substrate, and the formation of a low-oxygen site at the oxide-metal interface, thus reducing the solubility of O [4,5]. If the working temperature of the material is excessively high, Cr 2 O 3 will continue to oxidize to form volatile CrO 3 [6,7].…”