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采用激光逐层熔化沉积工艺制备了组织致密、定向性良好的DZ408镍基高温合金单道和多道扫描板状试样,对其沉积态显微组织的定向生长规律及成形机理进行了分析。结果表明,单道板试样表面光洁且形状规则,在沉积方向生成定向性良好的枝晶,而在扫描方向,枝晶受熔池形状影响,生长方向向扫描方向倾斜。多道板试样在垂直于扫描方向处,形成“Z”型组织,而在平行于扫描方向处,由于激光单道扫描结束时间长、冷却周期短,试样边界处沉积层的厚度是内侧沉积层的两倍,且熔池线向下塌陷;金属液由于重力超过表面张力而形成金属液滴,最终在多道板试样表面形成了大量金属瘤。
The dense and well-oriented DZ408 nickel-base superalloy single and multi-channel scanning plate samples were prepared by laser layer-by-layer melting deposition technique. The directional growth and the forming mechanism of the deposited microstructure were analyzed. The results show that the surface of the single track plate is smooth and regular in shape, and dendrite with good directivity is formed in the deposition direction. In the scanning direction, the dendrite is influenced by the shape of the molten pool, and the growth direction is inclined to the scanning direction. Multi-plate samples form “Z” -type tissue perpendicular to the scanning direction and parallel to the scanning direction due to the long laser end-of-scan length, short cooling period, the thickness of the deposited layer at the sample boundary Which is twice as much as the inner sedimentary layer, and the molten pool line collapses downward. Due to the gravitation exceeding the surface tension, the molten metal forms metal droplets, and finally a large number of metal tumors are formed on the surface of the multi-pass plate sample.