The fracture toughness of 617 Ni-based weld metal (WM) under different elevated temperatures was tested with a novel method and its fracture mechanism was investigated in this paper. It was found that the fracture toughness of WM was lower than that of base metal (BM) at the same temperature, which was mainly due to the coarse columnar structure, differences in misorientation, and precipitated phases. For both BM and WM, the fracture toughness was lower at elevated temperature due to decreased strength. Much more micro-voids caused by Ti(C, N) and M23C6 inside grains of BM could be observed adjacent to the crack path, which accounted for the dramatically decreased fracture toughness of BM at elevated temperature. In comparison, fewer micro-voids could be observed in WM due to the lack of those second particles. As a result, the J0.2 value and propagation path morphology both showed that the WM had more stable microstructure even though possessing lower toughness.

用一种新颖的方法测试了617 Ni基焊缝金属在不同高温下的断裂韧性，并研究了其断裂机理。发现在相同温度下，WM的断裂韧性低于贱金属（BM）的断裂韧性，这主要是由于粗大的柱状结构，取向差和析出相的缘故。对于BM和WM而言，由于强度降低，因此在高温下的断裂韧性较低。Ti（C，N）和M 23 C 6引起的更多微孔在裂纹路径附近可以观察到BM内部晶粒，这说明BM在高温下的断裂韧性急剧下降。相比之下，由于缺少那些第二粒子，在WM中可以观察到更少的微孔。结果，J 0.2值和传播路径形态均表明，尽管具有较低的韧性，但WM具有更稳定的微观结构。