Abstract
The environmental degradation of materials at high temperatures limits the useful life of different industrial components and hinders the development of more economical and environmentally friendly processes for the energy production. Despite the importance of this phenomena, a model to predict lifetime of materials that degrade due to high-temperature corrosion has up till now been lacking due to limitations of the computational possibilities and the complex nature of oxidation. In the present work we develop some strategies to model high-temperature corrosion in Fe-based alloys using the Calphad (Calculation of Phase Diagrams) approach. It is proposed that kinetic-based simulations for oxidation of Al and Cr can accurately represent the lifetime of the protective layers in FeCrAl and FeCr alloys at different temperatures in air. The oxide systems are in addition investigated by equilibrium calculations. The corrosion mechanisms of FeCr and FeCrAl alloys are discussed based on theoretical and experimental knowledge.
Highlights
Metallic materials designed for high-temperature applications must resist both mechanical and environmental degradation
We show that based on the experimental observations, the oxide scale formed on FeCr and FeCrAl alloys in air mostly consists of chromium oxide and aluminum oxide at 600 and 900 C, respectively
We first show the results from equilibrium calculations for the Fe-Cr-Al-O system
Summary
Metallic materials designed for high-temperature applications must resist both mechanical and environmental degradation. The environmental degradation of materials at high temperatures is an important issue in energy production, engines and industrial processes. It limits the useful life of installations, restricts the utilization of the fuel and hinders the development of more economical and environmentally friendly processes and systems. In corrosion resistant Fe-based alloys, environmental degradation due to high-temperature corrosion is controlled by the properties of the oxide scales that develop on the material. Low-alloy steels are normally used at low/medium temperatures, stainless steels (iron-based alloys with [ 12% Cr) are used at high-temperatures (T [ 500C) and/or in more corrosive environments while FeCrAl alloys are preferred at even higher temperatures. The protective layer of each of the mentioned alloys consists of iron oxide (steels), Cr-rich oxide of M2O3 (stainless steels) and Alrich M2O3 (FeCrAl alloys), respectively
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