采用激光逐层熔化沉积工艺制备出了DZ408高温合金板状试样，分析了其激光沉积态及热处理后的显微组织，测试合金的室温拉伸力学性能并分析了其断裂机理。结果表明，激光熔化沉积(LMD) DZ408镍基高温合金沿沉积方向具有快速凝固定向生长微细柱晶组织，其一次枝晶间距约为26 μm、二次枝晶间距约为8 μm，但在枝晶尺度范围内仍存在较明显的元素枝晶偏析，枝晶间γ′尺寸大于枝晶干。顶层沉积层由定向生长微细树枝晶和非定向树枝晶组成，相遇处由于合金液补缩不足产生疏松。在激光沉积过程中选择足够的重熔率，将非定向自由生长树枝晶层和疏松区重熔，是获得致密定向微细柱状晶的必要条件。经过后续热处理，测试合金的室温抗拉强度为1507 MPa，延伸率为14.5%。

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%.