Abstract:The content of Nb in GH4169 alloy powder was adjusted by ball milling alloying combining with laser additive manufacturing(LAM) technology. The effect of the composition adjustment on microstructure evolution of GH4169 superalloy by LAM was studied. The results showed that the typical microstructure of as-deposited GH4169 superalloy consisted of γ columnar dendrites growing epitaxially along the deposition direction. According to the theoretical results, the mixing enthalpy of alloy powder during LAM increased with the increase of Nb content, which made the growth direction of columnar crystal gradually changed from the deviation of the laser beam to the inward of the laser beam. The increase of solute concentration and the mixing enthalpy of alloy powder during LAM promoted the precipitation of γ+Laves interdendritic eutectics, and the morphology γ+Laves interdendritic eutectics was gradually like net. With the increase of Nb addition, the initial melting point of Laves phase increased, and the initial melting point of dendrite core γ phase decreased by DSC. The LAM alloying GH4169 changed the composition of the primary gamma phase, increasing the content of Nb element in the dendrite core. The highest concentration of Nb can reach 7.5wt.%. Therefore, the solid solution strengthening function of the Nb was enhanced.