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Cathodic cage plasma nitriding of austenitic stainless steel (AISI 316): influence of the working pressure on the nitrided layers properties
In this work, the influence of working pressure on the characteristics of the layers produced by the nitriding treatment on the AISI 316 austenitic stainless steel surface using the Cathodic Cage Plasma Nitriding technique (CCPN) is assessed. The treatments were carried out at a temperature of 723 K...
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Published in: | Materials research (São Carlos, São Paulo, Brazil) São Paulo, Brazil), 2014-04, Vol.17 (2), p.427-433 |
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Main Authors: | , , , , , |
Format: | Article |
Language: | English |
Subjects: | |
Citations: | Items that this one cites Items that cite this one |
Online Access: | Get full text |
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Summary: | In this work, the influence of working pressure on the characteristics of the layers produced by the nitriding treatment on the AISI 316 austenitic stainless steel surface using the Cathodic Cage Plasma Nitriding technique (CCPN) is assessed. The treatments were carried out at a temperature of 723 K for 5 hours under working pressures of 120, 250 and 500 Pa. The morphology, microstructure and corrosion resistance were studied through optical microscopy, x-ray diffraction, and electrochemical potential curves. We analyzed the effects of working pressure on the layer thickness, microhardness and corrosion resistance. The Exi curves and the electrochemical impedance of polarized samples were measured in order to investigate the effect of the ion transfer inside the produced film placed into the anodic solution. The electrochemical impedance of the films were measured, and showed an apparent capacitive behavior. For treatment under a pressure of 120 Pa we found the nitrides Fe sub(3)N, Fe sub(4)N and CrN. For treatment at a pressure of 250 Pa, the CrN disappears and the observed phases are the nitrides Fe sub(3)N, Fe sub(4)N and the S-phase. For a treatment pressure of 500 Pa there is an increase in the corrosion resistance of nitrided layers, confirmed by the predominance of S-Phase in the x-ray diffraction pattern. On the other hand, the sample nitrided under the pressure of 250 Pa showed very unstable impedance behavior when immersed in NaCl solution, indicating that the treatment at this specific working pressure has a negative effect on the corrosion resistance of plasma nitrided AISI 316 stainless steel surfaces. |
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ISSN: | 1516-1439 1980-5373 1980-5373 |
DOI: | 10.1590/S1516-14392013005000197 |