Effect of W Substitution on the Precipitation Behavior of χ and σ Phase in Super Duplex Stainless Steels

슈퍼 2상 스테인리스강에서 χ와 σ상의 석출거동에 미치는 W치환의 영향

Han, Huyn-Sung;Kim, Seong-Hwi;Kang, Chang-Yong

  • Received : 2015.12.18
  • Accepted : 2016.03.07
  • Published : 2016.04.27


This study was carried out to investigate the effect of W substitution on the precipitation behavior of ${\chi}$ and ${\sigma}$ phases in super duplex stainless steel. The ${\chi}$ phase was precipitated at the interface of ferrite / austenite phases and inside the ferrite phase at the initial stage of aging. With an increase in the aging time, the volume fraction of the ${\chi}$ phase increased, and then decreased with the transformation from the ${\chi}$ phase to the ${\sigma}$ phase. The ${\sigma}$ phase was precipitated later than the ${\chi}$ phase, and the volume fraction of x phase increased with the increase in the aging time. The ferrite phase was decomposed into the new austenite (${\gamma}2$) and ${\sigma}$ phases by aging treatment. The decomposition of the ferrite phase into the ${\gamma}2$ and ${\sigma}$ phases was retarded by W substitution for Mo. The volume fraction of the ${\chi}$ phase increased and that of the ${\sigma}$ phase decreased due to W substitution. The ${\chi}$ and ${\sigma}$ phases were intermetallic compounds, which had lower nickel concentration, and higher chromium, molybdenum, and tungsten concentrations. The ${\chi}$ phase has higher molybdenum and tungsten concentrations than those of the ${\sigma}$ phase. The amounts of chromium and nickel in the ${\chi}$ and ${\sigma}$ phases did not change, but these phases have higher concentrations of molybdenum and tungsten due to W substitution for Mo.


super duplex stainless steel;W substitution;${\chi}$-phase;${\sigma}$ phases;aging


  1. E. C. Bain and W. E. Griffiths, Trans AIME 75, 166 (1927).
  2. B. Soylu and R. W. K. Honeycombe, Mater. Sci. Technol., 7, 137 (1991).
  3. K. Oda, N. Kondo and K. Shibata, ISIJ Int., 30, 625 (1990).
  4. P. J. Uggowitzer, R. Magdowski and M. O. Speidel, ISIJ Int., 36, 901 (1996).
  5. Y. Maehara, Y. Ohmori, J. Murayama, N. Fujino and T. Kunitake, Metal. Sci., 17, 541 (1983).
  6. S. C. Kim, Z. Zang, Y. Furuya, C. Y. Kang, J. H. Sung, Q. Q. Ni, Y. Watanabe and I. S. Kim, Mater. Trans., 46, 1056 (2005).
  7. J. Cui, I. S. Park, C. Y. Kang and K. Miyahara, ISIJ Int., 41, 192 (2001).
  8. C. Y. Kang, H. S. Han, S. H. Lee and T. S. Han, J. Korean Soc. Heat Treat., 25, 74 (2012).
  9. S. Hertzman, B. Lehtinen and E. Symniotis-Barrdahl, Proc. Conf. "Stainless Steel 92", 345 (1992).
  10. T. Huhala, J. U. Nilson, A. Wilson and P. Jonson; Int. Conf. Duplex '94, p.43, Glasgow, Scotland, (1994).
  11. T. H. Hwang, J. H. Kim, W. J. Moon, K. H. Kim and C. Y. Kang, Met. Mater. Int., 20, 13 (2014).
  12. Y. S. Ahn and J. P. Kang, Mater. Sci. Technol., 16, 382 (2000).
  13. B. C. Lee, E. J. Oh and C. Y. Kang, Korean J. Mater. Res., 24, 610 (2014).
  14. J. M. Nicholls, Int. Conf. Duplex'94, Paper. KIII, Glasgow, Scotland, 13-16 November (1994).