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Microstructural Evolution of Grade 91 Steel upon Heating at 760~1000℃

  • He, Yinsheng (School of Nano & Advanced Materials Engineering, Changwon National University) ;
  • Chang, Jungchel (Technology Policy and Planning Department, Korea Electric Power Corporation) ;
  • Lee, Je-Hyun (School of Nano & Advanced Materials Engineering, Changwon National University) ;
  • Shin, Keesam (School of Nano & Advanced Materials Engineering, Changwon National University)
  • Received : 2015.07.27
  • Accepted : 2015.10.01
  • Published : 2015.11.27

Abstract

The microstructural evolution of Grade 91 tempered martensite ferritic steels heat treated at $760{\sim}1000^{\circ}C$ for two hours was investigated using scanning electron microscopy(SEM), energy disperse spectroscopy(EDS), electron backscattered diffraction (EBSD), and transmission electron microscopy(TEM); a microhardness tester was also employed, with a focus on the grain and precipitate evolution process as well as on the main hardening element. It was found that an evolution of tempered martensite to ferrite($760{\sim}850^{\circ}C$), and to fresh martensite($900{\sim}1000^{\circ}C$), occurred with the increase of temperature. Simultaneously, the parabolic evolution characteristics of the low angle grain boundary(LAGB) increased with the increase of the heating temperature(highest fraction of LAGB at $925^{\circ}C$), indicating grain recovery upon intercritical heating. The main precipitate, $M_{23}C_6$, was found to be coarsened slightly at $760{\sim}850^{\circ}C$; it then dissolved at $850{\sim}1000^{\circ}C$. Besides this, $M_3C$ cementite was formed at $900{\sim}1000^{\circ}C$. Finally, the experimental results show that the hardness of the steel depended largely on the matrix structure, rather than on the precipitates, with the fresh martensite showing the highest hardness value.

Acknowledgement

Supported by : National Research Foundation of Korea(NRF)

References

  1. D. Rojas, J. Garcia, O. Prat, G. Sauthoff and A. R. Kaysser-Pyzalla, Mater. Sci. Eng. A, 528, 5164 (2011). https://doi.org/10.1016/j.msea.2011.03.037
  2. V. Arunkumar, M. Vasudevan, V. Maduraimuthu and V. Muthupandi, Mater. Manuf. Processes, 27, 1171 (2012). https://doi.org/10.1080/10426914.2011.610212
  3. M. Yoshino, Y. Mishima, Y. Toda, H. Kushima, K. Sawada and K. Kimura, Mater. High Temp., 25, 149 (2008). https://doi.org/10.3184/096034008X356349
  4. T. C. Totemeier and J. A. Simpson, Proceedings from the Fourth International Conference on Advances in Materials Technology for Fossil Power Plants, 1242 (2004).
  5. T. Tokunaga, K. Hasegawa and F. Masuyama, Mater. Sci. Eng. A, 510-511, 158 (2009). https://doi.org/10.1016/j.msea.2008.05.059
  6. Y. He, J. Chang, J. Dong and K. Shin, Adv. Sci. Lett., 4, 1416 (2011). https://doi.org/10.1166/asl.2011.1697
  7. A. Aghajani, C. Somsen and G. Eggeler, Acta Mater., 57, 5093 (2009). https://doi.org/10.1016/j.actamat.2009.07.010
  8. B. Sonderegger, S. Mitsche and H. Cerjak, Mater. Sci. Eng. A, 481-482, 466 (2008). https://doi.org/10.1016/j.msea.2006.12.220
  9. C. G. Panait, W. Bendick, A. Fuchsmann, A. F. Gourgues-Lorenzon and J. Besson, Int. J. Pres. Ves. Pip., 87, 326 (2010). https://doi.org/10.1016/j.ijpvp.2010.03.017
  10. X. Guo, J. Gong, Y. Jiang and D. Rong, Mater. Sci. Eng., A, 564, 199 (2013). https://doi.org/10.1016/j.msea.2012.10.024
  11. L. Milovi , T. Vuherer, M. Zrili , A. Sedmak and S. Puti , Mater. Manuf. Processes, 23, 597 (2008). https://doi.org/10.1080/10426910802160544
  12. G. Dimmler, P. Weinert, E. Kozeschnik and H. Cerjak, Mater. Charact., 51, 341-352 (2003). https://doi.org/10.1016/j.matchar.2004.02.003
  13. T. Tokunaga, K. Hasegawa and F. Masuyama, Mater. High Temp., 27, 61 (2010). https://doi.org/10.3184/096034009X12604503186238
  14. M. Yoshino, Y. Mishima, Y. Toda, H. Kushima, K Sawada and K. Kimura, ISIJ Int., 5, 107 (2005).
  15. Y. Lin, C. C. Lin, T. H. Tsai and H. J. Lai, Mater. Manuf. Processes, 25, 246 (2010). https://doi.org/10.1080/10426910903426307