Unusual Microstructural Development upon Gaseous Nitriding of Fe-4.65at% Al Alloy

Abstract:

Employing NH3/H2 gas mixtures, Fe-4.65at% Al alloy specimens were nitrided to assess how the presence of Al, originally dissolved in the ferrite matrix, influences the development of γ-Fe4N1-x phase in the surface adjacent region. The nitrided specimens were characterized by light microscopy, X-ray diffraction, Electron Backscatter Diffraction and Electron Probe Micro Analysis. Surprisingly, formation of ε-Fe2N1-x was observed, although, for the applied nitriding parameters (nitriding potential and temperature), only the formation of γ-Fe4N1-x would be expected in case of nitriding pure ferrite. An unusual plate-type morphology of γ-Fe4N1-x was observed, contrasting with the usual continuous layer-type growth observed upon nitriding iron, Fe-Cr and Fe-V alloys. These unexpected phenomena may be explained as consequences of the need to realize a very high nitrogen supersaturation in the ferrite matrix in order to initiate the precipitation of AlN.

• Periodical: Advanced Materials Research (Volumes 89-91)
• Pages: 371-376
• DOI: https://doi.org/10.4028/www.scientific.net/AMR.89-91.371
• Online since: January 2010
• Authors: S. Meka, R.E. Schacherl, E. Bischoff, Eric Jan Mittemeijer
• Keywords: Aluminum Nitride (AlN), Fe-Al Alloy, Gas Nitriding, Iron Nitride

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