Thermal ageing and short-range ordering of Alloy 690 between 350 and 550 °C

Research output: Contribution to journalArticle


  • Roman Mouginot
  • Teemu Sarikka
  • Mikko Heikkilä
  • Mykola Ivanchenko
  • Ulla Ehrnstén
  • Young Suk Kim
  • Sung Soo Kim
  • Hannu Hänninen

Research units

  • University of Helsinki
  • VTT Technical Research Centre of Finland
  • Korea Atomic Energy Research Institute


Thermal ageing of Alloy 690 triggers an intergranular (IG) carbide precipitation and is known to promote an ordering reaction causing lattice contraction. It may affect the long-term primary water stress corrosion cracking (PWSCC) resistance of pressurized water reactor (PWR) components. Four conditions of Alloy 690 (solution annealed, cold-rolled and/or heat-treated) were aged between 350 and 550 °C for 10 000 h and characterized. Although no direct observation of ordering was made, variations in hardness and lattice parameter were attributed to the formation of short-range ordering (SRO) in all conditions with a peak level at 420 °C, consistent with the literature. Prior heat treatment induced ordering before thermal ageing. At higher temperatures, stress relaxation, recrystallization and α-Cr precipitation were observed in the cold-worked samples, while a disordering reaction was inferred in all samples based on a decrease in hardness. IG precipitation of M23C6 carbides increased with increasing ageing temperature in all conditions, as well as diffusion-induced grain boundary migration (DIGM).


Original languageEnglish
Pages (from-to)56-66
Number of pages11
JournalJournal of Nuclear Materials
Publication statusPublished - 1 Mar 2017
MoE publication typeA1 Journal article-refereed

    Research areas

  • Alloy 690, Carbide precipitation, Cold work, NiCr, Short-range ordering, Strain localization, Thermal ageing

ID: 10461988