The effect of thermal aging on fracture properties of a narrow-gap Alloy 52 dissimilar metal weld

In nuclear power plants, dissimilar metal welds belong to safety class 1. The effect of thermal aging at 400 °C up to 15 000 h on ductile-to-brittle transition (DBT) region was investigated for an Alloy 52 dissimilar metal weld (DMW). The cracks and the notches were placed close to the fusion boundary between the low-alloy steel (LAS) and the weld metal. In previous work for DMWs, the shifts in different DBT temperatures have not been investigated, including reference temperature T0, impact toughness-based T28J and reference temperature for arrest toughness, TKIa. The results show that the T0 reference temperature does not change significantly with aging time, only 10 °C, but the shift in T28J is 49 °C after 15 000 h. The shift in TKIa is 35 °C. The results indicate that the aging mechanism affects more the crack propagation and arrest properties than brittle fracture initiation