(西北工业大学 凝固技术国家重点实验室，
西安 710072)
摘 要: 利用FGH95合金粉末在DD3单晶基材和定向凝固镍基高温合金的择优晶面（与择优晶向垂直的晶面）上进行激光多层涂覆实验，得到了从基材外延生长的单晶涂覆层。 涂层由细小柱状枝晶组织组成， 枝晶一次间距约为10μm， 二次臂退化。 由于局部凝固条件的不同， 枝晶干区域的γ′相为球形、 枝晶间区的γ′相为立方体形态， 尺度均小于0.1μm。 激光涂覆层中的主要元素Cr和Co的偏析比基材铸态组织中的偏析大大减轻。 对标准热处理后的试样进行分析表明: 试样中的γ′相主要为方圆形， 且尺度均匀。 涂层中各元素的显微偏析比热处理之前有明显减轻。沿片状力学性能试样柱状晶生长方向进行拉伸， 强度指标达到同种材料粉末冶金试件的97.9%， 塑性超过粉末冶金试件。断口分析表明， FGH95合金的断裂机制为塑性断裂。
关键字: 激光成形定向凝固； FGH95； 成分偏析； 力学性能
（State Key Laboratory of Solidification Processing, Northwestern Polytechnical University,Xi'an 710072, China）
Abstract:Laser multi-layer cladding experiments were performed on the preferential crystallography surface (plane normal to the preferential crystallography orientation) of the DD3 single crystal rod and the directional solidification nickel-base superalloy rod by using superalloy FGH95 powder. Cladding layers growing epitaxially from the substrate can be obtained. The cladding layer consists of thin columnar dendritic, the primary arm spacing of which is about 10μm, and the secondary arm is degenerated. γ′ deposits are spherical in the dendritic trunk and cubical in the interdendritic area due to the difference of the local elements aggregation. The sizes of γ′ phase are less than 0.1μm. Composition segregation of main elements in the cladding layer are highly alleviated on comparing with that of the substrate. After heat treatment, the γ′ deposits become cubic-spherical in the cladding layer and the size of them is more homogeneous in all of the single crystal cladding layers. Composition segregation is alleviated further after heat treatment. Mechanical measurement shows that yield strength acquires 97.9% of that in powder metallurgic sample and the plasticity surpasses that in powder metallurgic sample, and the fracture of FGH95 shows plastic fracture.
Key words: laser metal forming; directional solidification; FHG95; composition segregation; mechanical property
