A 16Cr-25Ni superaustenitic stainless steel weld metal for austenitic stainless steel/ferrite heat-resistance steel dissimilar metal weld was designed and prepared through tungsten inert-gas welding. The precipitate evolution and its correlation with mechanical properties were investigated during post-weld heat treatment (PWHT) at 690 °C for up to 12 h. The primary precipitates in the as-welded weld metal were identified as Mo-rich M₆C carbides in the interdendritic region and semicontinuous fine-sized M₂₃C₆ carbides along grain boundary. After PWHT, three types of precipitates coexisted in the interdendritic region: primary M₆C carbides, newly precipitated Mo-rich M₂X carbonitrides and some of the secondary M₂₃C₆ carbides. Additionally, mass secondary M₂₃C₆ carbides formed and coarsened along grain boundary. No undesirable intermetallic phases formed during the whole period. The M₂X and interdendritic M₂₃C₆ improved the strength of the weld metal after PWHT, but the elongation and impact toughness degraded, which were mainly owing to the intergranular M₂₃C₆ carbides that changed the fracture mode from ductile transgranular mode to mixed mode of transgranular and intergranular fracture. Meanwhile, the coarsening of M₂X carbonitrides may lead to the elongation loss during 8 h to 12 h. Evolution of impact toughness was also related to the M₂X carbonitrides, which made the crack easier to propagate compared with austenitic matrix and contributed to the decline of impact toughness. However, due to the sluggish precipitation of M₂X carbonitrides with longer holding time, the decreasing trend became slow from 4 to 12 h. The results showed that PWHT should be controlled within 8 h to obtain better combination of strength and ductility.

通过钨极惰性气体保护焊设计制备了一种用于奥氏体不锈钢/铁素体耐热钢异种金属焊缝的16Cr-25Ni超奥氏体不锈钢焊缝金属。在 690 °C 下进行长达 12 小时的焊后热处理 (PWHT) 期间，研究了沉淀物的演变及其与机械性能的相关性。焊态焊缝金属中的主要析出物被确定为枝晶间区域的富钼M ₆ C 碳化物和沿晶界的半连续细小尺寸M ₂₃ C ₆碳化物。PWHT后，枝晶间区域共存三种析出物：初生M ₆ C碳化物，新析出的富钼M ₂X碳氮化物和一些次生M ₂₃ C ₆碳化物。此外，大量二次M ₂₃ C ₆碳化物形成并沿晶界粗化。在整个过程中没有形成不良的金属间相。的中号₂ X和枝晶间中号₂₃ Ç ₆改进PWHT后的焊接金属的强度，但延伸率和冲击韧性降低，这主要是由于晶界中号₂₃ Ç ₆碳化物的断裂模式从韧性穿晶断裂模式转变为穿晶断裂和沿晶断裂混合模式。同时，M ₂ X碳氮化物的粗化可能导致8 至12 小时的伸长率损失。冲击韧性的演变也与M ₂ X碳氮化物有关，与奥氏体基体相比，它使裂纹更容易扩展，导致冲击韧性下降。然而，由于M ₂ X碳氮化物的缓慢沉淀和较长的保温时间，下降趋势从4 小时到12 小时变得缓慢。结果表明，焊后热处理应控制在 8 h 内，以获得更好的强度和延展性组合。