Tetsu-to-Hagane
Online ISSN : 1883-2954
Print ISSN : 0021-1575
ISSN-L : 0021-1575
Transformations and Microstructures
Strengthening Mechanism in Nitrogen Diffusion Layer of Nitrocarburized Fe-C-Mn Steel
Masato Yuya Naoyuki SanoShigefumi NishitaniMotoki Takasuga
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2018 Volume 104 Issue 2 Pages 81-87

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Abstract

Steels containing 0.3mass%C and various amount of Mn were nitrocarburized at 873 K for 2 h to investigate behavior of N and Mn in a nitrocarburized layer. Transmission electron microscopy observation showed that a part of Mn precipitated as nitrides η-Mn3N2 in the ferrite matrix. To fix the state of N in the nitrocarburized layer, solution and aging treatments were carried out sequentially. Most N was presumed to exist as dissolved N or Mn nitrides in the solution treated specimen and as iron or Mn nitrides in the aged specimen. Amount of the precipitation hardening with η-Mn3N2 increased with the increasing Mn content, whereas amount of solid solution hardening in the steel with high Mn content was smaller than that with low Mn content. On the basis of measuring N concentration and thermodynamical calculation, it was estimated that the precipitation hardening ability of Mn nitrides was smaller than that of Cr, Al, Ti and V nitrides.

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© 2018 The Iron and Steel Institute of Japan

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