Electrochemical Characteristics of Delta Ferrite in Thermally Aged Austenitic Stainless Steel Weld

  • Gokul Obulan Subramanian
  • Sunghoon Hong
  • Ho Jung Lee
  • Byeong Seo Kong
  • Kyoung-Soo Lee
  • Thak Sang Byun
  • Changheui JangEmail author
Conference paper
Part of the The Minerals, Metals & Materials Series book series (MMMS)


An austenitic stainless steel Type 316L weld was thermally aged for 20,000 h at 400 °C and electrochemical characterization was performed to measure corrosion resistance in δ–ferrite phase. It is well known that a severe thermal aging causes decrease of fracture resistance and increase of the hardness of δ–ferrite, which was related to the spinodal decomposition. After thermal aging, the DL-EPR response of 316L weld was dominated by parent austenite matrix without reactivation peak. To characterize the δ–ferrite only, austenite phase was selectively dissolved from the matrix by electrochemical etching method. The double–loop electrochemical potentiokinetic reactivation (DL-EPR) analysis of the δ–ferrite phase showed degradation in corrosion resistance after thermal aging with the appearance of a cathodic loop and reactivation peak during the reverse scan. The degradation in corrosion resistance of δ–ferrite phase could be attributed to the localized Cr-depletion due to spinodal decomposition and precipitation of intermetallic phases during thermal aging.


DL-EPR analysis Stainless steel weld Thermal aging Corrosion Delta ferrite 



This study is mainly supported by the Korea Hydro and Nuclear Power Co., Ltd. as the Proactive Material Aging Management Project. Part of the funding is provided as Nuclear R&D Program (2015M2A8A2074798) of the MSIP/NRF of Rep. of Korea. Financial support for three of the authors is provided by the BK-Plus Program of the MSIP of Rep. of Korea.


  1. 1.
    K. Chandra, V. Kain, V.S. Raja, R. Tewari, G.K. Dey, Low temperature thermal ageing embrittlement of austenitic stainless steel welds and its electrochemical assessment. Corros. Sci. 54, 278–290 (2012)CrossRefGoogle Scholar
  2. 2.
    D.J. Alexander, K.B. Alexander, M.K. Miller, R.K. Nanstad, Y.A. Davidov, The effect of aging at 343 °C in the microstructure and mechanical properties of type 308 stainless steel weldments” (Report NUREG/CR-6628, Oak Ridge National Laboratory, 2000)Google Scholar
  3. 3.
    O.K. Chopra, Estimation of fracture toughness of cast stainless steels during thermal aging in LWR systems (Report NUREG/CR-4513, Argonne National Laboratory, 1994)Google Scholar
  4. 4.
    O.K. Chopra, W.J. Shack, “Mechanical properties of thermally aged cast stainless steels from Shippingport reactor components” (Report NUREG/CR-6275, Argonne National Laboratory, 1995)Google Scholar
  5. 5.
    S.A. David, J.M. Vitek, D.J. Alexander, Embrittlement of austenitic stainless steel welds. J. Nondestr. Eval. 15, 129–136 (1996)CrossRefGoogle Scholar
  6. 6.
    T.P.S. Gill, J.B. Gnanamoorthy, A method for quantitative analysis of delta–ferrite, sigma and M23C6 carbide phases in heat treated Type 316 stainless steel weldments. J. Mater. Sci. 17, 1513–1518 (1982)CrossRefGoogle Scholar
  7. 7.
    S. Hong, H. Kim, B.S. Kong, C. Jang, I.H. Shin, J.-S. Yang, K.-S. Lee, Evaluation of the thermal ageing of austenitic stainless steel welds with 10% of δ–ferrites, Int. J. Press. Vessels Pip. (2017) (In press)Google Scholar
  8. 8.
    J.-S. Lee, K. Fushimi, T. Nakanishi, Y. Hasegawa, Y.-S. Park, Corrosion behaviour of ferrite and austenite phases on super duplex stainless steel in a modified green–death solution, Corros. Sci. 89, 111–117 (2014)CrossRefGoogle Scholar
  9. 9.
    I. Chattoraj, S.K. Das, S. Jana, S.P. Chakraborty, A.K. Bhattamishra, Passivity breakdown due to discontinuous precipitation during ageing of 21Cr–10Mn–5Ni stainless steel. J. Mater. Sci. 30, 5313–5320 (1995)CrossRefGoogle Scholar
  10. 10.
    H. Böhni, T. Suter, F. Assi, Micro-electrochemical techniques for studies of localized processes on metal surfaces in the nanometer range. Surf. Coat. Technol. 130, 80–86 (2000)CrossRefGoogle Scholar
  11. 11.
    C.J. Park, H.S. Kwon, M.M. Lohrengel, Micro-electrochemical polarization study on 25% Cr duplex stainless steel. Mater. Sci. Eng., A 372, 180–185 (2004)CrossRefGoogle Scholar
  12. 12.
    L. Dong, Q. Peng, E. Han, W. Ke, L. Wang, Stress corrosion cracking in the heat affected zone of a stainless steel 308L-316L weld joint in primary water. Corros. Sci. 107, 172–181 (2016)CrossRefGoogle Scholar
  13. 13.
    D.J. Edwards, L.E. Thomas, K. Asano, S. Ooki, S.M. Bruemmer, Microstructure, microchemistry and stress corrosion crack characteristics in a BWR 316L SS core shroud weld (Paper presented at the 13th International Conference on Environmental Degradation of Materials in Nuclear Power Systems—Water Reactors, 2007)Google Scholar
  14. 14.
    K.N. Krishnan, K.P. Rao, Effect of microstructure on stress corrosion cracking behaviour of austenitic stainless steel weld metals. Mater. Sci. Eng., A 142, 79–85 (1991)CrossRefGoogle Scholar
  15. 15.
    H. Abe, Y. Watanabe, Role of δ-ferrite in stress corrosion cracking retardation near fusion boundary of 316NG welds. J. Nucl. Mater. 424, 57–61 (2012)CrossRefGoogle Scholar

Copyright information

© The Minerals, Metals & Materials Society 2019

Authors and Affiliations

  • Gokul Obulan Subramanian
    • 1
  • Sunghoon Hong
    • 1
  • Ho Jung Lee
    • 1
  • Byeong Seo Kong
    • 1
  • Kyoung-Soo Lee
    • 2
  • Thak Sang Byun
    • 3
  • Changheui Jang
    • 1
    Email author
  1. 1.Department of Nuclear and Quantum EngineeringKAISTDaejeonRepublic of Korea
  2. 2.Central Research Institute, KHNPDaejeonRepublic of Korea
  3. 3.Pacific Northwest National LaboratoryRichlandUSA

Personalised recommendations