| 1. |
- Ge, Y., et al.
(författare)
-
Effect of thermal aging on microstructure and carbides of SA508/Alloy 52 dissimilar metal weld
- 2023
-
Ingår i: Materials Characterization. - 1044-5803. ; 200
-
Tidskriftsartikel (refereegranskat)abstract
- 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.
|
|
| 2. |
- Lindgren, Kristina, 1989, et al.
(författare)
-
Post-irradiation annealing of high flux irradiated and surveillance material reactor pressure vessel weld metal
- 2022
-
Ingår i: Journal of Nuclear Materials. - : Elsevier BV. - 0022-3115 .- 1873-4820. ; 562
-
Tidskriftsartikel (refereegranskat)abstract
- In this study, high flux irradiated and surveillance high Ni and Mn and low Cu welds identical to those of the belt-line region of Ringhals R4 were subjected to annealing at temperatures between 390 and 455 °C for 24–30 h, in order to study the dissolution of irradiation induced clusters and possible matrix defects using hardness testing and atom probe tomography. It was found that the cluster characteristics did not change during annealing at 390 °C, meaning that the size, number density and composition of the clusters, which mainly consist of Ni and Mn, did not change. Thus, the observed decrease in hardness during annealing of the high flux irradiated material is believed to be due to dissolution of matrix defects that were stable at the operating temperature. Cluster dissolution was observed after annealing at 410 °C in the high flux irradiated material, leaving around 10% of the original clusters. These clusters contained more Cu and less Ni and Mn than before annealing. The cluster dissolution at temperatures above 400 °C correlated with the decrease in hardness. The larger clusters of the surveillance material required a higher temperature or longer time to be dissolved compared to the clusters of the high flux material.
|
|
| 3. |
- Que, Zaiqing, et al.
(författare)
-
Brittle fracture initiation in decommissioned boiling water reactor pressure vessel head weld
- 2022
-
Ingår i: Journal of Nuclear Materials. - : Elsevier BV. - 0022-3115 .- 1873-4820. ; 569
-
Tidskriftsartikel (refereegranskat)abstract
- The brittle fracture initiation behavior and fracture toughness in the ductile-to-brittle transition region for a thermally-aged weld metal of a decommissioned reactor pressure vessel head (in operation at 288 degrees C for 23 effective full power years) and in the non-aged reference condition were investigated. The results show that brittle fracture initiated primarily from non-metallic inclusions. The correlation between frac-ture toughness and brittle fracture initiation type (inclusion debonding or breakage), initiator size, initi-ation location (as-welded or re-heated regions in the weld metal) were analysed. Despite that thermal ageing does not affect significantly the fracture toughness, it could promote the debonding as a brit-tle fracture primary initiation type. The influence of debonded inclusion on the evolution of cumulative damage and brittle fracture initiation was assessed using crystal plasticity modelling.
|
|
