激光熔覆钴基合金非对称宏观形貌形成机理及微观特性研究

Asymmetric Macro-Morphologies Formation Mechanism and Microscopic Characteristics of Co-Based Alloys by Laser Cladding

采用YLS-3000光纤激光器开展了激光熔覆钴基高温合金实验,通过光学显微镜、显微硬度计表征了激光熔覆钴基高温合金的宏观形貌、显微组织和显微硬度。结果表明:由于激光熔覆过程前序熔覆对后续熔覆有预热作用,在不同激光熔覆参数作用下,熔覆层的宽度分别由起始的4.84,5.17,5.88mm逐渐过渡到熔覆末尾的5.28,6.61,6.78mm,激光熔覆区域的上表面形貌为喇叭形;由于激光熔覆的送粉方向和相邻的激光熔覆对基体的预热作用,激光熔覆形貌为非对称性月牙形;在表面熔覆层中心区域可观察到等轴晶,在内部熔覆层中部可观察到非均匀树枝晶。由于激光熔覆过程的非平衡凝固、不同区域的加热和冷却速度差异,熔覆层的硬度呈现非均匀性分布,且都高于基体硬度。

The YLS-3000 fiber laser is used to laser cladding of the Co-based superalloy.The macro-morphology,microstructure and microhardness of Co-based superalloy after laser cladding are characterized by the optical microscope and the microhardness tester.The results show that due to the preheating effect of the preceding cladding process on the subsequent cladding process,the widths of the cladding layer gradually transit from the initial 4.84,5.17,5.88 mm to the cladding-terminal 5.28,6.61,6.78 mm,respectively under the effects of different laser cladding parameters.The upper surface morphology of laser cladding area is horn shape.The morphology of laser cladding is asymmetric crescent shape due to the powder feeding direction during laser cladding and the preheating effect of adjacent laser cladding on the substrate.The equiaxed grains are observed in the central area of surface cladding layer and the non-uniform dendrites are observed in the middle of inner cladding layer.Because of the non-equilibrium solidification in the process of laser cladding and the differences between heating rates and cooling ones in different sections,the hardness of the cladding layer presents a non-uniform distribution,and is always higher than the hardness of its substrate.