Journal of the Korean Society for Heat Treatment (열처리공학회지)

The Korean Society for Heat Treatment (한국열처리공학회)
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Phase Changes of the STS 431 Martensitic Stainless Steel after High Temperature Gas Nitriding Treatment

STS 431 마르텐사이트계 스테인리스강의 고온 가스 질화 열처리에 따른 상변화

  • 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)
  • Received : 2008.10.24
  • Accepted : 2008.11.21
  • Published : 2008.09.30
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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

References

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