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摘要
The element of Nb in GH4169 alloy powder was adjusted by ball milling alloying combined with laser additive manufacturing (LAM) technology. The effect of the composition adjustment on microstructure evolution of GH4169 superalloy by LAM was studied. The results show that the typical microstructure of as-deposited GH4169 superalloy consists of γ columnar dendrites growing epitaxially along the deposition direction. According to the theoretical results, the mixing enthalpy of the alloy powder during LAM increases with the increase of Nb content, which makes the growth direction of columnar crystal gradually change 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 promotes the precipitation of γ+Laves interdendritic eutectics, and the morphology of γ+Laves interdendritic eutectics gradually becomes net-like. With the increase of Nb addition, the initial melting point of Laves phase increases, and the initial melting point of dendrite core γ phase decreases by DSC. The LAM alloyed GH4169 changes the composition of the primary γ phase, increasing the content of Nb element in the dendrite core. The highest concentration of Nb can reach 7.5 wt%. Therefore, the solid solution strengthening function of Nb is enhanced.
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