Ni-base superalloy FM-52M is mainly used in welded structures of key equipment of nuclear power plants, such as pressure vessels and heat dissipation evaporators. It is prone to form coarse columnar microstructures during welding and has significant ductility dip cracking (DDC) susceptibility. This work attempted to introduce micrometre-sized TiC particles into FM-52M welds to refine the microstructure and alleviate sensitivity to DDC. A Ni–TiC coating with good dispersion and uniformity of TiC particles was first prepared on the substrate by composite electroplating. The TiC particles were then directly introduced into the molten pool during tungsten–inert gas welding. Scanning electron microscopy and electron backscatter diffraction were used to analyse the microstructure of the weld and strain-to-fracture testing was performed to evaluate its DDC sensitivity. The experimental results showed that solidification grains of the weld were obviously refined and its high-temperature mechanical properties were reinforced. The minimum critical strain for DDC increased to approximately 3.5%, and the crack morphology was small and tortuous. Compared with the original material, the microstructure and DDC resistance of the weld were improved by introducing TiC particles.

镍基高温合金FM-52M主要用于核电站关键设备（如压力容器和散热蒸发器）的焊接结构。它易于在焊接过程中形成粗大的柱状微结构，并具有显着的延性浸裂（DDC）敏感性。这项工作试图将微米级的TiC颗粒引入FM-52M焊缝中，以改善微观结构并减轻对DDC的敏感性。首先通过复合电镀在基材上制备具有良好分散性和均匀性的TiC颗粒的Ni–TiC涂层。然后在钨极惰性气体保护焊过程中将TiC颗粒直接引入熔池中。使用扫描电子显微镜和电子反向散射衍射分析焊缝的微观结构，并进行应变至断裂测试以评估其DDC敏感性。实验结果表明，焊缝的凝固晶粒明显细化，其高温力学性能得到增强。DDC的最小临界应变增加到大约3.5％，并且裂纹形态小而曲折。与原始材料相比，通过引入TiC颗粒改善了焊缝的显微组织和DDC电阻。裂纹形态小而曲折。与原始材料相比，通过引入TiC颗粒改善了焊缝的显微组织和DDC电阻。裂纹形态小而曲折。与原始材料相比，通过引入TiC颗粒改善了焊缝的显微组织和DDC电阻。