Abstract
Oxide growth and the induced stresses in the high-temperature oxidation of steel were studied by a multiphase field model. The model incorporates both chemical and elastic energy to capture the coupled oxide kinetics and generated stresses. Oxidation of a flat surface and a sharp corner are considered at two high temperatures of 850 °C and 1180 °C to investigate the effects of geometry and temperature elevation on the shape evolution of oxides and the induced stresses. Results show that the model is capable of capturing the oxide thickness and its outward growth, comparable to the experiments. In addition, it was shown that there is an interaction between the evolution of oxide and the generated stresses, and the oxide layer evolves to reduce stress concentrations by rounding the sharp corners in the geometry. Increasing the temperature may increase or decrease the stress levels depending on the contribution of eigen strain in the generated elastic strain energy during oxidation.
Highlights
Designs of advanced energy systems such as nuclear power plants, combustion boilers, and steam and gas turbines, require materials that reliably work in complex and harsh environments under various mechanical, chemical, and thermal loads and contaminations [1,2]
The reported oxide phase that formed in short-time oxidation is FeO with a rock slat crystal structure that formed on the surface of the steel substrate
The effect of geometry on the interaction between oxide coupling mechanical equilibrium equations to the phase-field equations, the evolution of stresses evolution and induced stresses was studied by considering oxidation on a flat substrate and a sharp corner
Summary
Designs of advanced energy systems such as nuclear power plants, combustion boilers, and steam and gas turbines, require materials that reliably work in complex and harsh environments under various mechanical, chemical, and thermal loads and contaminations [1,2]. Yang et al analyzed high-temperature oxidation of Fe-based alloys using PFM [40] Even though their results showed good agreement with experimental results, their work did not consider the effect of geometry and temperature change on the stress generation, and their model did not allow the capture of outward oxidation. Following the experimental observations by Chen and Yuen [31], where they observed only the formation of the FeO oxide phase in a short time period of the oxidation of steel, our model considered only one phase of oxide, but the model was developed in a way that can be later advanced to study the multiphase oxidation of steels The model incorporates both chemical and elastic energies and is capable of capturing outward oxide growth, elemental concentration changes as well as the evolution of induced stresses. Different temperatures and geometries are considered to investigate the effect of these parameters on the interaction between generated stresses and oxide layer evolution
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