Verification on Possibility of Nitrogen Diffusion into Steel by High Temperature N-Quench

Abstract:

N-Quench, which is a new surface heat treatment to infiltrate nitrogen into steel parts followed by quenching to achieve hardening, is gathering attention in the nitriding field as it affords low distortion while maintaining a higher effective case depth (ECD) compared with conventional nitriding. N-Quench is conducted mainly between 680°C and 800°C, where the two-phase region of ferrite and austenite exists in the Fe-N phase diagram. However, a few studies have reported on nitriding at temperatures higher than 800°C due to decomposition of NH₃, which is a key source of nitrogen infiltration. Our results revealed that in a conventional furnace such as resistance heating furnace, no nitrogen infiltrated the specimen at 930°C, which is the general carburizing temperature. On the other hand, in the infrared heating furnace, nitrogen infiltrated the specimen at 930°C successfully with lesser NH₃ introduction than that required by the conventional furnace. Therefore, in this study, the limit of NH₃ decomposition is assessed and possibility of extending the applicability of N-Quench, especially increasing the ECD while maintaining a low distortion, is examined.

• Periodical: Defect and Diffusion Forum (Volume 395)
• Pages: 124-132
• DOI: https://doi.org/10.4028/www.scientific.net/DDF.395.124
• Online since: August 2019
• Authors: Atsushi Nakamura*, Koichiro Nambu, Masahiro Okumiya
• Keywords: Carburization, Effective Case Depth, Nitriding, Nitrogen Infiltration, N-Quench

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