In this work, ultrasonic micro-forging treatment (UMFT) was introduced to achieve homogeneous microstructure, reduce defects and improve mechanical properties of GH3039 superalloy cladding layer processed by directed energy deposition (DED). The microstructure, defects and mechanical properties of the cladding layers treated by UMFT with different ultrasonic powers (UIPs) were investigated. Results revealed a gradient structure as equiaxed grains distributed at the top, a columnar-to-equiaxed transition (CET) region that mixed of columnar dendrites and equiaxed grains distributed at the middle and columnar dendrites at the bottom of the cladding layer was formed. After UMFT, the proportion of equiaxed grains was increased, the average size of equiaxed grains was refined to 10 μm from 16 μm, the orientation of grains was more uniform and the phases enriched of Al, Ti, C, Nb and Mo were precipitated. The grain refinement can be attributed to the fracture of columnar dendrites induced by the ultrasonic vibration during solidification. Besides, the porosity of the cladding layer was reduced after UMFT. The microhardness of the cladding layers exhibited a depth-dependent gradient at the top region. The microhardness of the top surface was the highest and showed an increasing trend with the increase of UIP. The microhardness of different grain morphologies exhibited no substantial difference. However, due to grain refinement and precipitation of strengthening phase induced by UMFT, the microhadness of some local locations were improved. These results indicated UMFT has a significant effect on improving the microstructure, defects and mechanical properties of the deposited cladding layer.

在这项工作中，引入了超声微锻造处理（UMFT），以实现通过定向能量沉积（DED）处理的GH3039高温合金熔覆层的均匀组织，减少缺陷并改善机械性能。研究了用不同超声功率（UIP）的UMFT处理的包覆层的组织，缺陷和力学性能。结果揭示了一种梯度结构，等轴晶粒分布在顶部，形成了柱状-等轴过渡（CET）区域，该区域混合了柱状枝晶和分布在覆层底部中部和柱状枝晶的等轴晶粒。UMFT后，等轴晶粒的比例增加，等轴晶粒的平均尺寸从16μm细化到10μm，晶粒的取向更加均匀，并且析出了富集Al，Ti，C，Nb和Mo的相。晶粒细化可归因于凝固过程中超声振动引起的柱状枝晶的断裂。此外，UMFT后降低了包层的孔隙率。包层的显微硬度在顶部区域显示出深度相关的梯度。顶面的显微硬度最高，并且随着UIP的增加而增加。不同晶粒形貌的显微硬度没有实质性差异。然而，由于UMFT引起的晶粒细化和强化相的析出，某些局部位置的微观硬度得到了改善。这些结果表明UMFT对改善微观结构具有显著作用，