Microstructural study of Alloy 690 base metal and HAZ from mockup components – Influence of Ti(C,N) banding
2014 (English)In: Fontevraud 8 - Contribution of Materials Investigations and Operating Experience to LWRs’ Safety, Performance and Reliability, SFEN , 2014Conference paper (Refereed)
The Alloy 690 base metal and heat affected zones (HAZs) of three component mockups have been studied using light optical microscopy and scanning electron microscopy. All mockups were manufactured as part of the production of replacement components using commercial heats. Welding and post weld heat treatments were performed in the same way as for components in field in order to obtain microstructures representative to the ones in operating plants.
All three Alloy 690 base metals exhibited Ti(C,N) banding, but to a different extent. In all cases, the bands extended through the material’s longitudinal direction. In two of these materials the Ti(C,N) bands were correlated with M23C6 carbide coarsening, fine grain banding and reduced grain boundary tortuosity in the longitudinal direction.
Full carbide dissolution was observed near the fusion line. The coarser carbides in the banded regions were overall less affected, but were also fully dissolved when close enough to the fusion line. The region affected by carbide dissolution spanned roughly 300‑1000 μm wide depending on mockup. The Ti(C,N) precipitates however appeared unaffected. The lack of carbides near the fusion line, where the weld induced strains typically are highest, suggest that inducing cold work after a solution anneal may produce a material more representative of the HAZ than cold working the material in the thermally treated state.
Place, publisher, year, edition, pages
SFEN , 2014.
Alloy 690, heat affected zone, microstructure, banding, carbides
Research subject Solid Mechanics
IdentifiersURN: urn:nbn:se:kth:diva-164099OAI: oai:DiVA.org:kth-164099DiVA: diva2:803809
Fontevraud 8 Fontevraud 8 - Contribution of Materials Investigations and Operating Experience to LWRs’ Safety, Performance and Reliability, 15-18 September, 2014
NQC 20152015-04-132015-04-132015-04-14Bibliographically approved