Laser multi-layer cladding experiment on the DD3 single crystal using FGH95 powder: Investigation on the microstructure of single crystal cladding layer

Laser multi-layer cladding experiments were performed on the substrate of DD3 single crystal with FGH95 powder as cladding material. The solidification microstructure in the sample was investigated. It was found that the solidification microstructure was greatly influenced by the crystallography orientation of the substrate and the local solidification conditions. When the angle between the preferred orientation of the single crystal and the direction of heat flow in the cladding layer is less than 30°, single crystal cladding layers were acquired. Otherwise the crystallography orientation of the cladding layer will deviate from the orientation of the substrate and the microstructure with polycrystalline appears. Meanwhile, even when the experiments were performed on the same preferred crystal surface, the solidification microstructures will be different distinctly resulting from the variation of the local solidification conditions. The secondary arms were degenerated and the primary arm spacing was about 10-20 μm. Further investigation shows that the phases of the cladding layer are mainly made up of γ,γ′, the flower-like γ/γ′ eutectic and carbide. The morphology of γ′ was cubical and the size is less than 0.1 μm.