罗建,谢颂伟,毛家智,王梁,张群莉,葛鸿浩,姚建华.稳态磁场对激光熔覆钴基合金宏观偏析及元素扩散影响[J].表面技术,2022,51(12):320-328, 349.
LUO Jian,XIE Song-wei,MAO Jia-zhi,WANG Liang,ZHANG qun-li,GE hong-hao,YAO Jian-hua.Effect of a Steady Magnetic Field on the Macro-segregation and Element Diffusion of Laser Cladding Cobalt-based Alloy[J].Surface Technology,2022,51(12):320-328, 349 |
| 稳态磁场对激光熔覆钴基合金宏观偏析及元素扩散影响 |
| Effect of a Steady Magnetic Field on the Macro-segregation and Element Diffusion of Laser Cladding Cobalt-based Alloy |
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| DOI：10.16490/j.cnki.issn.1001-3660.2022.12.033 |
| 中文关键词: 激光熔覆 稳态磁场 熔池 宏观偏析 元素扩散 |
| 英文关键词:laser cladding steady magnetic field molten pool macro-segregation element diffusion |
| 基金项目:国家自然科学基金重点项目(52035014);浙江省科技计划(公益技术)(LGG19E050024);浙江省属高校基本科研业务费专项资金(RF-C2019003) |
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| Author | Institution |
| LUO Jian | College of mechanical Engineering,Institute of Laser Advanced Manufacturing Zhejiang University of Technology, Hangzhou 310000, China;Collaborative Innovation Center of High-end Laser Manufacturing Equipment Co-sponsored by Ministry and Province, Hangzhou 310000, China |
| XIE Song-wei | College of mechanical Engineering,Institute of Laser Advanced Manufacturing Zhejiang University of Technology, Hangzhou 310000, China;Collaborative Innovation Center of High-end Laser Manufacturing Equipment Co-sponsored by Ministry and Province, Hangzhou 310000, China |
| MAO Jia-zhi | College of mechanical Engineering,Institute of Laser Advanced Manufacturing Zhejiang University of Technology, Hangzhou 310000, China;Collaborative Innovation Center of High-end Laser Manufacturing Equipment Co-sponsored by Ministry and Province, Hangzhou 310000, China |
| WANG Liang | College of mechanical Engineering,Institute of Laser Advanced Manufacturing Zhejiang University of Technology, Hangzhou 310000, China;Collaborative Innovation Center of High-end Laser Manufacturing Equipment Co-sponsored by Ministry and Province, Hangzhou 310000, China |
| ZHANG qun-li | College of mechanical Engineering,Institute of Laser Advanced Manufacturing Zhejiang University of Technology, Hangzhou 310000, China;Collaborative Innovation Center of High-end Laser Manufacturing Equipment Co-sponsored by Ministry and Province, Hangzhou 310000, China |
| GE hong-hao | College of mechanical Engineering,Institute of Laser Advanced Manufacturing Zhejiang University of Technology, Hangzhou 310000, China;Collaborative Innovation Center of High-end Laser Manufacturing Equipment Co-sponsored by Ministry and Province, Hangzhou 310000, China |
| YAO Jian-hua | College of mechanical Engineering,Institute of Laser Advanced Manufacturing Zhejiang University of Technology, Hangzhou 310000, China;Collaborative Innovation Center of High-end Laser Manufacturing Equipment Co-sponsored by Ministry and Province, Hangzhou 310000, China |
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| 中文摘要: |
| 目的 探究稳态磁场对熔覆层宏观偏析及元素扩散的影响机制，为调控熔覆层元素分布提供理论指导。方法 采用同轴送粉方式，利用稳态磁场辅助激光熔覆制备钴基合金熔覆层。通过光学显微镜和扫描电子显微镜，对有无宏观偏析区域的元素含量进行半定量测量，分析了不同磁场强度条件下熔覆层的显微组织及元素扩散规律。结果 在无磁场时，宏观偏析主要存在于熔覆层底部，部分分布于熔覆层上层区域，并有一定的扩散现象。加入稳态磁场后，由于稳态磁场产生的感应洛伦兹力与熔池流动方向相反，抑制了熔池对流，宏观偏析出现聚集现象，且无明显扩散。加入稳态磁场后，熔覆层宏观偏析区域具有较高的Fe含量，最高质量分数可达67.9%，这与基体中的Fe含量接近。熔覆层无宏观偏析区域Co的质量分数增加了8%，Fe的质量分数降低了12.1%，熔覆层底部宏观偏析面积占比由10%增加到25%。结论 稳态磁场能够使宏观偏析产生富集，使更多的Fe元素存在于熔池底部，同时抑制Fe元素在熔覆层中扩散。稳态磁场有效降低了基体元素对熔覆层的稀释，使无宏观偏析区域的元素含量与粉末的元素含量更为接近。 |
| 英文摘要: |
| The substrate material was 316L austenitic stainless steel and the CL (Cladding layer) material was Cobalt-based alloy powder. In order to avoid the interference of the magnetic field in the LC (Laser cladding) process, both the substrate and the cladding powder are non-ferromagnetic. Cobalt-based coatings were prepared by LC assisted with a steady magnetic field. The maximum magnetic flux intensity is 1.8 T. During the experiment, the sample was kept stationary, while the laser head was moved to scan the substrate. The powder was injected into the molten pool through carrier gas with the laser coaxially. The surface of the corroded sample is observed with Optical metallographic microscope (OM), Scanning electron microscope (SEM), and the composition of the CL is analyzed by Energy dispersive spectrometer (EDS). The morphology of the molten pool changes obviously when the steady magnetic field is applied. With the increase of the magnetic flux density, the electromagnetic damping gradually increases, which reduces the convexity of the solidification line of the molten pool and made the bottom of the molten pool smoother. Without magnetic field, the macro-segregation moves with molten pool fluid, which is evenly distributed in the upper region of the CL after sufficient stirring and diffusion. Since the fluid velocity at the bottom of the molten pool is lower than that of the upper layer, the macro-segregation at the bottom of the molten pool is more obvious. The proportion of the macro-segregation area in the CL changes from low to high from the surface to the bottom. With the magnetic flux density increases, the proportion of the macro-segregation area in the entire CL gradually increases. With magnetic field, due to the damping effect on fluid flow, the macro-segregation can be completely retained in the molten pool without being dispersed. The zone without macro-segregation maintains a high content of Co and a low content of Fe. When there is no magnetic field, the Fe element at the zone of macro-segregation is diffused to the surrounding area, resulting in an increase of Fe element the zone of without macro-segregation. When the magnetic field is added, the Fe content in the zone around the macro-segregation is significantly reduced compared with the case without magnetic field. It is indicated that the diffusion of Fe element at the macro-segregation is suppressed by the steady magnetic field. Since the liquidus temperature TLB (1 370 ℃) of the powder alloy is lower than the liquidus temperature TLC (1 440 ℃) of the matrix, when the liquid matrix metal is brought into the molten pool with low temperature by convection, it will be quickly solidified in the molten pool. With the increase of magnetic flux density, the Hartmann number of the molten pool gradually increases and the distribution is uneven. Due to the lower temperature and higher conductivity at the bottom of the molten pool, the Hartmann number at the bottom of the molten pool is higher than the top of the molten pool. It is shown that the equivalent viscosity at the bottom of the molten pool is higher than that at the top of the molten pool. This phenomenon leads to severe macro-segregation at the bottom of the molten pool and suppresses the diffusion of macro-segregation to the surrounding area. The steady magnetic field suppresses the diffusion of macro-segregation in the CL, reduces the dilution of solute elements, and obtains the CL which is closer to the cladding powder. |
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