Thermal aging of reactor pressure vessel steel welds at elevated temperatures may affect the ductile-to-brittle transition temperature. In this study, unique weld material from a pressurizer, with a composition similar to that of the reactor pressure vessel, that has been in operation for 28 years at 345 °C is examined. Despite the relatively low temperature, the weld becomes hardened during operation. This is attributed to nanometre sized Cu-rich clusters, mainly located at Mo- and C-enriched dislocation lines and on boundaries. The welds have been characterized using atom probe tomography, and the characteristics of the precipitates/clusters is related to the hardness increase, giving the best agreement for the Russell-Brown model.

反应堆压力容器钢焊缝在高温下的热老化可能会影响韧性到脆性的转变温度。在这项研究中，检查了来自增压器的独特焊接材料，其组成与反应堆压力容器的相似，并且已在345°C下运行了28年。尽管温度相对较低，但焊接在操作过程中仍会变硬。这归因于纳米级的富铜团簇，主要位于富钼和富碳位错线以及边界上。已经使用原子探针断层扫描对焊缝进行了表征，并且析出物/团簇的特征与硬度的增加有关，这为Russell-Brown模型提供了最好的一致性。