Investigation on the Microstructure and Segregation of Superalloy FGH96 by Direct Laser Forming

Direct laser forming directional solidification experiments were performed by using nickel-base superalloy as substrate and powder FGH96 as cladding material. The solidification microstructure of the cladding layer was investigated. Results showed that as-deposited microstructure was directionally solidified dendrites with the primary dendrite arm spacing of approximately 3 mu m and the secondary arm was small or even degenerated. According to the theory of columnar/equiaxed transition(CET) in front of the solid/liquid interface, it was found that in the single-path multi-layer cladding layers and multi-path multi-layer cladding layers, the microstructure with the same crystallographic orientation as the substrate was obtained by reasonably selecting the processing parameters. Composition segregation analysis showed a very uniform distribution of elements,and the segregation ratios were close to 1.