Synthesis, thermodynamic stability and diffusion mechanism of Al 5Fe2-based coatings
Abstract
Aluminide coating of steels enables more efficient power generation through higher operating temperatures. Low-temperature (T < 660 C) pack cementation aluminide coatings form an Al5Fe2 phase which allows for the development of a large Al flux, but the mechanism is not clear. The coating structures and resultant oxides were examined in both austenitic and ferritic steels at 1,000 and 800 C to evaluate the high temperature oxidation behavior in air. To understand the relatively fast Al diffusion, the stability of the Al5Fe2 phase and the defect structure have been examined by a cluster expansion method with density functional theory calculations. The Al5Fe2 phase has a low site occupancy and a high vacancy content that promotes rapid kinetics. The high vacancy concentration in the Al5Fe2 phase can be traced to the interaction between Al and vacancies along the [001] chains. The analysis offers useful guidance to enable an effective control of low temperature aluminizing.
Document Type
Conference Proceeding
DOI
https://doi.org/10.1007/s11085-013-9463-2
Keywords
Al Fe 5 2, Aluminide coatings, Density functional theory, Pack defect structure
Publication Date
2-1-2014
Recommended Citation
Sakidja, R., J. H. Perepezko, and P. Calhoun. "Synthesis, thermodynamic stability and diffusion mechanism of Al 5 Fe 2-based coatings." Oxidation of metals 81, no. 1 (2014): 167-177.
Journal Title
Oxidation of Metals
