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Microstructural Characterization and Formation Mechanism of Nitrided Layers on Aluminum Substrates by Thermal Plasma Nitriding

1
Key Laboratory of Automobile Materials, School of Materials Science and Engineering, Jilin University, Changchun 130025, China
2
BMW Brilliance Automotive Ltd., Shenyang 110044, China
*
Author to whom correspondence should be addressed.
Metals 2019, 9(5), 523; https://doi.org/10.3390/met9050523
Received: 5 April 2019 / Revised: 27 April 2019 / Accepted: 5 May 2019 / Published: 7 May 2019
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Abstract

Nitrided layers on 6082 aluminum alloy substrates and 1060 aluminum substrates are formed at atmospheric pressure using thermal nitrogen plasma, which only takes seconds to form a millimeter-level layer. The nitrided layers are composed of aluminum nitride (AlN) and aluminum solid solution phases. Microstructures in these nitrided layers can be divided into three regions from bottom to top: the transition region, the dendrite region, and the lamella region. These regions are formed in sequence. The formation mechanisms and processes of the three regions are discussed in detail. Furthermore, we found that Al melt is transported upward through the voids and the capillaries in the AlN structures, and reacts with N plasma in the melt surface. The growth of the AlN structures promotes this transport. With the increase of N2 flow rates from 1 L/min to 7.5 L/min, both the hardness and the wear resistance of the nitrided layers are improved, and the nitrided layer becomes thicker. View Full-Text
Keywords: thermal nitrogen plasma; aluminum nitride; formation mechanism; nitrided layer; mechanical properties thermal nitrogen plasma; aluminum nitride; formation mechanism; nitrided layer; mechanical properties
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Li, X.; Xin, W.; Zheng, X.; Ren, Z.; Sun, D.; Lu, W. Microstructural Characterization and Formation Mechanism of Nitrided Layers on Aluminum Substrates by Thermal Plasma Nitriding. Metals 2019, 9, 523.

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