• Mouginot, Roman
• Hänninen, Hannu
• Sarikka, Teemu
• Iyanchenko, Mykola
• Ehrnsten, Ulla
• Heikkilä, Mikko J.
• Kim, Sung Soo
• Kim, Young Suk

Abstract

<p>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) coniponents. Four conditions of Alloy 690 (solution annealed, cold-rolled and/or heat-treated) were aged between 350 and 550 degrees 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 degrees C, consistent with the literature. Prior heat treatment induced ordering before thermal ageing. At higher temperatures, stress relaxation, recrystallization and alpha-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). (C) 2016 Elsevier B.V. All rights reserved.</p>

Topics

• impedance spectroscopy
• grain
• grain boundary
• carbide
• hardness
• precipitation
• aging
• recrystallization
• stress corrosion