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Controlling Nitrogen Dose Amount in Atmospheric-Pressure Plasma Jet Nitriding

1
Division of Electrical and Electronic Engineering, Oita University, Oita 870-1192, Japan
2
Department of Electronic Engineering, Tohoku University, Sendai 980-8579, Japan
3
Material Technology Division, Fukuoka Industrial Technology Center, Kitakyushu 807-0831, Japan
*
Author to whom correspondence should be addressed.
Metals 2019, 9(6), 714; https://doi.org/10.3390/met9060714
Received: 25 April 2019 / Revised: 24 June 2019 / Accepted: 24 June 2019 / Published: 25 June 2019
(This article belongs to the Special Issue Plasmas Processes Applied on Metals and Alloys)
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Abstract

A unique nitriding technique with the use of an atmospheric-pressure pulsed-arc plasma jet has been developed to offer a non-vacuum, easy-to-operate process of nitrogen doping to metal surfaces. This technique, however, suffered from a problem of excess nitrogen supply due to the high pressure results in undesirable formation of voids and iron nitrides in the treated metal surface. To overcome this problem, we have first established a method to control the nitrogen dose amount supplied to the steel surface in the relevant nitriding technique. When the hydrogen fraction in the operating gas of nitrogen/hydrogen gas mixture increased from 1% up to 5%, the nitrogen density of the treated steel surface drastically decreased. As a result, the formation of voids were suppressed successfully. The controllability of the nitrogen dose amount is likely attributable to the density of NH radicals existing in the plume of the pulsed-arc plasma jet. View Full-Text
Keywords: plasma nitriding; atmospheric-pressure plasma; nitrogen dose amount; hydrogen fraction; void plasma nitriding; atmospheric-pressure plasma; nitrogen dose amount; hydrogen fraction; void
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).
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Ichiki, R.; Kono, M.; Kanbara, Y.; Okada, T.; Onomoto, T.; Tachibana, K.; Furuki, T.; Kanazawa, S. Controlling Nitrogen Dose Amount in Atmospheric-Pressure Plasma Jet Nitriding. Metals 2019, 9, 714.

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