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- Title
Microstructural Changes of Al Hot-Dipped P91 Steel during High-Temperature Oxidation.
- Authors
Abro, Muhammad Ali; Dong Bok Lee
- Abstract
The 9Cr-1Mo steel (ASTM P91) was hot-dip aluminized, and its microstructural changes during oxidation were studied. Before oxidation, the coating consisted of (Al-rich topcoat containing a small amount of Al5Fe2 and Al13Fe4)/(Al13Fe4-rich, Al13Fe4-containing alloy layer)/(Al5Fe2 alloy layer containing a small amount of Al9Cr4precipitates), from the surface. During oxidation at 700-900 ±C for 20-100 h, Al diffused inward and the substrate elements migrated outward to broaden and soften the coating, and also to transform (high Al)-Fe intermetallics to (low Al)-Fe intermetallics. The phases in the coating progressively transformed during oxidation as follows; (Al-rich topcoat)/(Al5Fe2-rich, Al13Fe4-containing alloy layer)/(Al5Fe2 alloy layer)→(α-Al2O3 scale)/(Al13Fe4-rich, Al5Fe2-containing layer)/(Al5Fe2 layer)/(AlFe interlayer)→(α-Al2O3 scale)/(AlFe-rich, Al5Fe2-containing layer)/(AlFe layer)/(AlFe3 layer))→((α-Al2O3, Fe2O3)-mixed scale)/(AlFe3 layer)/(Fe(Al) layer) from the surface. As the oxidation progressed, the scale changed from α-Al2O3 to the (α-Al2O3, Fe2O3)-mixture, which provided the necessary oxidation resistance.
- Subjects
STEEL investment casting; FERRITIC steel corrosion; THERMAL properties of surface coatings
- Publication
Coatings (2079-6412), 2017, Vol 7, Issue 2, p31
- ISSN
2079-6412
- Publication type
Article
- DOI
10.3390/coatings7020031