TY - JOUR
T1 - Effect of thermal aging on microstructure and carbides of SA508/Alloy 52 dissimilar metal weld
AU - Ge, Yanling
AU - Que, Zaiqing
AU - Lindgren, K.
AU - Hytönen, Noora
AU - Thuvander, M.
N1 - The authors wish to express their gratitude for the funding and support from Ringhals AB, OKG AB, Teollisuuden Voima Oyj and VTT Technical Research Centre of Finland within the FEMMA (Forum for the Effect of Thermal Aging and Microstructure on Mechanical and EAC Behavior of Ni-based Alloy Dissimilar Metal Welds) research project. The authors also thank NKS for funding the NKS-FEMMA (AFT/NKS-R(22)134/4) project. The authors would like to thank P. Arffman, J. Lydman, J. Lukin and L. Sirkiä for the experimental contributions. The authors would like to thank U. Ehrnstén, P. Efsing, B. Forssgren, H. Reinvall and H. Hänninen for suggestions and discussions. The authors acknowledge the provision of facilities and technical support by Aalto University at OtaNano - Nanomicroscopy Center (Aalto-NMC). The APT experiments were performed at Chalmers Materials Analysis Laboratory (CMAL).
PY - 2023/6/1
Y1 - 2023/6/1
N2 - A narrow-gap SA508/Alloy 52 dissimilar metal weld (DMW) mock-up, fully representative of an actual nuclear component, was investigated in this work. The microstructure and carbides formed in the low alloy steel fusion boundary (FB) and heat affected zone (HAZ) can act as brittle fracture initiators and could influence the brittle fracture behavior. However, the amount of information available in the open literature on the microstructural changes and carbide formation in DMW occurring upon post-weld heat treatment and long-term thermal aging is very limited. The microstructure and carbide type, morphology and size in the carbide precipitation zone (CPZ, up to 1.5 μm from FB), carbon depletion zone (CDZ, up to 40–50 μm from FB) and HAZ (up to 2 mm from FB) of the plant-relevant DMW in post-weld heat-treated and thermally-aged (400 °C for 15,000 h, corresponding to 90 years of operation) conditions were analyzed with analytical electron microscopy, wide-angle X-ray scattering and atom probe tomography. Long-term thermal aging increases the microhardness peak close to the FB, triples the width of the CPZ and coarsens the carbide size in the HAZ (up to a magnitude). There is no evidence of a significant phosphorus segregation to grain boundaries due to thermal aging.
AB - A narrow-gap SA508/Alloy 52 dissimilar metal weld (DMW) mock-up, fully representative of an actual nuclear component, was investigated in this work. The microstructure and carbides formed in the low alloy steel fusion boundary (FB) and heat affected zone (HAZ) can act as brittle fracture initiators and could influence the brittle fracture behavior. However, the amount of information available in the open literature on the microstructural changes and carbide formation in DMW occurring upon post-weld heat treatment and long-term thermal aging is very limited. The microstructure and carbide type, morphology and size in the carbide precipitation zone (CPZ, up to 1.5 μm from FB), carbon depletion zone (CDZ, up to 40–50 μm from FB) and HAZ (up to 2 mm from FB) of the plant-relevant DMW in post-weld heat-treated and thermally-aged (400 °C for 15,000 h, corresponding to 90 years of operation) conditions were analyzed with analytical electron microscopy, wide-angle X-ray scattering and atom probe tomography. Long-term thermal aging increases the microhardness peak close to the FB, triples the width of the CPZ and coarsens the carbide size in the HAZ (up to a magnitude). There is no evidence of a significant phosphorus segregation to grain boundaries due to thermal aging.
KW - Alloy 52
KW - Carbides
KW - Dissimilar metal welds
KW - Narrow gap
KW - Thermal aging
UR - http://www.scopus.com/inward/record.url?scp=85151542232&partnerID=8YFLogxK
U2 - 10.1016/j.matchar.2023.112880
DO - 10.1016/j.matchar.2023.112880
M3 - Article
SN - 1044-5803
VL - 200
JO - Materials Characterization
JF - Materials Characterization
M1 - 112880
ER -