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对铸造定向DZ125镍基高温合金进行单道多层的激光成形修复实验。通过光镜、扫描电镜及透射电镜对修复区进行微观组织观察,使用电子探针测定不同相及修复区枝晶干的成分。结果表明:通过激光成形修复的方法可以获得自原基材外延生长的细小定向γ柱状晶修复组织,仅在修复区顶部存在部分取向杂乱的等轴晶组织;相比铸造定向基材,沉积态修复区呈现快速外延定向凝固特征,导致修复区的成分偏析减轻,枝晶间MC型碳化物相比基材显著细化,呈块状或正八面体状,枝晶间同时分布有γ+γ′共晶组织;另外,在γ枝晶干分布着近100 nm的球形γ′相,且部分γ′相颗粒有相互连接的现象。总体上,修复区一次枝晶间距、碳化物及γ′相尺度比修复基材显著细化。
Single shot multilayered laser forming repair experiment of casting oriented DZ125 nickel base superalloy. The microstructure of the repair area was observed by light microscopy, scanning electron microscopy and transmission electron microscopy, and the composition of dendrite dryness in different phases and repaired area was determined by electron probe. The results show that the microstructure of the fine oriented γ columnar crystal grown epitaxially from the original substrate can be obtained by laser forming and repairing, and the misoriented equiaxed crystal structure exists only at the top of the repaired area. Compared with the cast oriented substrate, The repaired areas show rapid epitaxial directional solidification characteristics, resulting in the reduction of component segregation in the repaired area. The MC type interdendritic grains are significantly refined compared with the substrate, and are massive or regular octahedron with dendritic distribution of γ + γ ’ Eutectic. In addition, spherical γ ’phase near 100 nm is distributed in γdendrites, and some γ’ phase particles are connected to each other. In general, the primary dendrite spacing, carbide and γ ’phase size in the repaired area are significantly refined than that of the repaired substrate.