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采用横流 5 k W CO2 激光 ,在 Ni基高温合金表面制备了纳米 Al2 O3/ Ni基合金复合材料激光熔覆层。利用光学显微镜、扫描电镜 (SEM)及附件 (EDS)分析了熔覆层的快速凝固组织、成分及纳米颗粒的分布。结果表明 ,未加纳米 Al2 O3时界面区为垂直于界面、定向生长的柱状树枝晶组织 ;加入纳米 Al2 O3后 ,熔池凝固结晶组织形态发生变化 ,由细长的柱状树枝晶逐步过渡为较短的树枝晶 ;当 Al2 O3的加入量为 1%时 ,熔覆层与基体的界面区不出现定向生长 ,整个断面呈现等轴枝晶组织 ;纳米 Al2 O3促进固液界面前沿形核 ,纳米 Al2 O3附着在晶体生长的前沿 ,阻碍晶体的长大 ,凝固组织得到显著细化 ;纳米 Al2 O3颗粒抑制了熔覆层裂纹的形成。
The laser cladding layer of Al 2 O 3 / Ni-based alloy nanocomposite was prepared on the surface of Ni-based superalloy using a cross-flow 5 k W CO2 laser. The microstructure, composition and nanoparticle distribution of the coating were analyzed by optical microscopy, scanning electron microscopy (SEM) and attachment (EDS). The results show that the interface zone is perpendicular to the interfacial growth of columnar dendrites without addition of Al 2 O 3. The morphology of the solidified and crystallized melt pool changes with the addition of Al 2 O 3 nanostructures. The transition from slender columnar dendrites to Short dendrites. When the content of Al 2 O 3 is 1%, the interfacial region between the cladding layer and the substrate does not appear directional growth, and the whole cross section presents equiaxed dendrite structure. The nano Al 2 O 3 promotes the nucleation at the front of the solid- Al 2 O 3 adheres to the front of the crystal growth, hindering the growth of the crystal, and remarkably refining the solidified structure. The nano-Al 2 O 3 particles inhibit the formation of cracks in the cladding layer.