激光增材制造Nb合金化GH4169合金组织分析

Microstructure of Nb alloying treated GH4169 superalloy prepared by laser additive manufacturing

摘要:

采用球磨合金化的方式，在常规GH4169合金粉末中添加Nb元素，利用激光增材制造技术成形了具有不同Nb含量的GH4169试样，研究了Nb含量对激光增材制造GH4169合金组织的影响。结果表明：激光增材制造Nb合金化GH4169合金显微晶粒结构仍为粗大柱状晶组织；随着Nb含量的增加，合金粉末在熔池中合金化反应放热量增多，使得柱状晶的生长方向由偏离激光束中心向外生长逐渐变化为朝向激光束中心向内生长。由于熔池中溶质浓度和粉末熔化放热量的增加，使得枝晶间γ+Laves共晶组织的数量增多，逐渐形成连续网状的共晶组织；DSC分析结果发现，随着Nb元素添加量的增加，共晶Laves相的初熔点升高，枝晶干γ相的熔点略有降低。另外，合金化改变了初生γ相的成分，枝晶干Nb元素含量最高浓度达到7.5wt.%，合金固溶强化作用得到加强。

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.