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Phase Changes of the STS 431 Martensitic Stainless Steel after High Temperature Gas Nitriding Treatment  

Yoo, D.K. (Steel Making Department, Hyundai Steel Company)
Kong, J.H. (Department of Materials Science and Engineering, Dong-A University)
Lee, H.W. (Department of Materials Science and Engineering, Dong-A University)
Kang, C.Y. (Division of Materials Science and Engineering, Pukyong National University)
Kim, Y.H. (Knowledge-based Mechanical Parts and Materials R&D Cluster, Dong-A University)
Sung, J.H. (Knowledge-based Mechanical Parts and Materials R&D Cluster, Dong-A University)
Publication Information
Journal of the Korean Society for Heat Treatment / v.21, no.5, 2008 , pp. 244-250 More about this Journal
Abstract
This study has investigated the surface phase change, hardness variation, surface precipitates, nitrogen content and corrosion resistance in STS 431 (17Cr-2Ni-0.2C-0.01Nb) martensitic stainless steel after high temperature gas nitriding (HTGN) treatment at the temperature range between $1050^{\circ}C$ and $1150^{\circ}C$. The HTGN-treated surface layer appeared $Cr_2N$ of rod type, carbo-nitride of round type and fine precipitates in the austenite matrix. On the other hand the interior region where the nitrogen was not permeated, exhibited martensite phase. The surface hardness showed 250~590 HV, depending on the HTGN treatment conditions, while the interior martensitic phase represented 520 HV. The permeation depth of nitrogen increased with increasing the HTGN-treated temperature. The nitrogen concentration of the surface layer appeared approximately ~0.17% at $1100^{\circ}C$. On comparing the corrosion resistance between solution-annealed and HTGN-treated steels, the corrosion resistance of HTGN-treated steel was superior to that of solution-annealed specimens.
Keywords
STS431 (17Cr-2Ni-0.2C-0.01Nb); High temperature gas nitriding (HTGN); Austenite matrix; Cr2N; carbo-nitride; Corrosion resistance;
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Times Cited By KSCI : 2  (Citation Analysis)
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