Microstructure and mechanical properties of rapid solidified ultra-fine columnar grain Ni-base superalloy DZ408 by laser melting deposition manufacturing

Directionally rapid solidified Ni-base superalloy DZ408 with ultra-fine columnar grain structure is produced by the laser melting deposition (LMD) manufacturing process. Microstructure and mechanical properties of the laser melting deposited DZ408 before and after heat treatment are analyzed and tested. Results show that as-deposited microstructure is directionally solidified dendrites with the primary dendrite arm spacing of approximately 26 μm and the secondary dendrite arm spacing of approximately 8 μm . The size of γ' in the interdendritic zones is larger than that in the dendritic cores. The undirectional columnar layer and interdendritic shrinkage should be sufficient remelted to ensure the densification and epitaxy between the depositing layer and the previous one. After proper heat treatment, the room temperature tensile strength of the DZ408 superalloy is 1507 MPa, while the elongation along the deposition direction is 14.5%.