Development of Short-Range Order and Intergranular Carbide Precipitation in Alloy 690 TT upon Thermal Ageing

Roman Mouginot, Teemu Sarikka, Mikko Heikkilä, Mykola Ivanchenko, Unto Tapper, Ulla Ehrnstén, Hannu Hänninen

Research output: Contribution to journalConference articleScientificpeer-review

Abstract

Thermal ageing promotes intergranular carbide precipitation and atomic ordering reaction in most commercial nickel-base alloys, and it affects the long-term primary water stress corrosion cracking (PWSCC) resistance of pressurized water reactor components. Alloy 690 with 9.8 wt% Fe was solution annealed and heat-treated at low temperature, then aged between 350 and 550 °C for 10,000 h. No direct observation of ordering was possible, but variations in hardness and lattice parameter suggested the formation of short-range ordering (SRO) with a peak level upon ageing at 420 °C, while a disordering reaction occurred at higher temperatures. Heat treatment induced ordering before thermal ageing was compared to the solution-annealed state. Thermal ageing resulted in the precipitation of Cr-rich M23C6 carbides at grain boundaries and twin boundaries. Although no link between SRO and an increase in strain localization was observed, the combination of intergranular carbide formation and SRO over longer ageing times was deemed detrimental to the PWSCC resistance of Alloy 690 TT
Original languageEnglish
JournalThe minerals, metals & materials series
Pages (from-to)321-334
Number of pages14
ISSN2367-1181
DOIs
Publication statusPublished - 2018
MoE publication typeA4 Article in conference proceedings
EventInternational conference on environmental degradation of materials in nuclear power systems-water reactors - Portland, Oregon, United States
Duration: 13 Aug 201717 Aug 2017
Conference number: 18

Fields of Science

  • 116 Chemical sciences
  • 114 Physical sciences

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