Title: Investigation of the intermediate layers formed by austenitic nitrocarburising

Authors: Melinda Godzsák; Péter Pekker; Ildikó Cora; Zsolt Veres

Addresses: Faculty of Materials Science and Engineering, Institute of Physical Metallurgy, Metalforming and Nanotechnology, University of Miskolc, Miskolc 3515, Hungary ' Faculty of Materials Science and Engineering, Institute of Physical Metallurgy, Metalforming and Nanotechnology, University of Miskolc, Miskolc 3515, Hungary ' Centre for Energy Research, Institute of Technical Physics and Materials Science, Thin Films Department, P.O. Box 49, H-1525 Budapest, Hungary ' Faculty of Materials Science and Engineering, Institute of Physical Metallurgy, Metalforming and Nanotechnology, University of Miskolc, Miskolc 3515, Hungary

Abstract: By nitriding the Fe-N system above the eutectoid temperature (592°C), an intermediate layer called (nitro)austenite is formed under the compound layer that can transform into braunite during low-rate cooling at eutectoid temperature. The two-phase complement of structure forming such a way - namely the braunite - is an eutectoid consisting of body-centred cubic α-iron and Fe₄N iron-nitride compound (α + γ´). This poorly investigated texture and its formation was investigated. During our experiments, 100Cr6 and C105U steels were nitrocarburised above the eutectoid temperature (592°C). The conditions and properties of the formation of the developed intermediate layers, the microstructure and the distribution of the nitrogen and carbon in the specimens were investigated by using light optical microscopy (LOM), microhardness measurements, X-ray diffraction (XRD) method, scanning (SEM) and transmission (TEM) electronmicroscopy and glow discharge optical emission spectrometry (GD-OES).

Keywords: braunite; nitroaustenite; nitrogen pearlite; iron nitride; eutectoid temperature; intermediate layers; austenitic nitrocarburising; steel; microstructure; carbon.

DOI: 10.1504/IJMMP.2016.078038

International Journal of Microstructure and Materials Properties, 2016 Vol.11 No.1/2, pp.34 - 47

Received: 26 Mar 2015
Accepted: 21 Aug 2015
Published online: 31 Jul 2016 *

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