镍基高温合金的激光焊接在航天器金属热防护系统以及火箭发动机等关键结构制造中具有重要应用，但对焊接质量要求很高，必须有效抑制全熔透激光焊接的飞溅和焊缝中的匙孔型工艺气孔缺陷。此前，相关研究工作国内外鲜有报道。本文基于航天制造工程需求，以Inconel 617合金全熔透激光焊接工艺为对象开展镍基高温合金激光焊接质量控制技术研究。论文通过实验研究和理论分析发现，镍基高温合金结构采用软规范参数（较低功率匹配较低焊速）及较高热输入时，空间施焊位置对激光焊接质量有明显的影响：横焊和立向下焊过程中，熔池金属流动和凝固行为影响气泡形成与浮出过程，从而导致焊缝存在较为严重的气孔缺陷。对于航天器复杂形面的结构件，需通过机器人和变位机的协调控制，尽可能采取平焊或立向上施焊。而当采用硬规范（较高功率匹配较高焊速）及较低热输入时，焊接位置对激光焊接质量的影响较小。所以，在设备条件允许情况下尽量采用硬规范参数。研究发现，镍基高温合金结构激光焊接时呈现匙孔周期性穿透熔池的状态。匙孔穿透熔池时，熔池正面等离子体羽焰形态及亮度剧烈波动，从熔池背面出口向外喷射金属蒸气、等离子体和焊接飞溅，但匙孔穿透熔池有利于抑制熔池内匙孔型气孔形成。因此，提出在保证全熔透焊缝成形前提下优化焊接速度和激光功率参数组合的技术准则：调节匙孔周期性穿透熔池时间占比，以综合抑制镍基高温合金横焊的激光焊缝内部气孔和背面飞溅。采用激光束摆动方式并综合优化摆动频率、摆动幅度等工艺参数，可抑制镍基高温合金焊缝内部气孔缺陷的生成。通过匹配合适的激光功率参数保证中厚板焊接在匙孔模式下稳定进行，实现了高质量的全熔透激光焊接。焊接工艺参数对镍基高温合金激光焊接接头显微组织及力学性能有明显影响。高热输入条件下，熔化区中部晶粒尺寸粗大，取向杂乱，枝晶间距较大，枝晶间碳化物颗粒尺寸较为粗大，枝晶间Mo、Cr等强化元素的凝固偏析较为严重，从而造成焊缝强度弱化。通过论文研究工作所形成的镍基高温合金激光焊接质量控制技术已应用在我国航天制造领域，带动相关产品激光焊接质量与生产效率明显提高。

Laser welding of nickel-based superalloys has important applications in the key structures of spacecraft manufacture such as metal thermal protection systems and rocket engines. But its requirements for welding quality is very high. The spatter and the keyhole-induced porosity defect must be effectively suppressed during the full-penetration laser welding process. The related research was rarely reported before. This thesis studies the quality control technology of full-penetration laser welding of nickel-based superalloys based on the requirements of aerospace manufacturing engineering,.The experimental research and theoretical analysis of the thesis show that when lower power, lower welding speed, and higher heat input are adopted as parameters in the nickel-based superalloys welding, the welding position has a significant impact on the quality of laser welding: During the horizontal down and vertical down welding process, the flow and solidification behavior of the molten pool metal affects the formation and emergence of bubbles, resulting in serious porosity defects in the weld. For the spacecraft structural parts with complex surfaces, flat welding or vertical welding are better choices achieved through the coordinated control of the robot and the positioner. When taking higher power, higher welding speed, and low heat input parameters, the welding position has little influence on the quality of laser welding, which should be used as far as equipment conditions permit.The research found that the keyhole periodically penetrates the molten pool during laser welding of nickel-based superalloy structures. When the keyhole penetrates the molten pool, the shape and brightness of the plasma plume on the front of the molten pool fluctuate violently. Metal vapor, plasma and welding spatter are sprayed out from the outlet on the back of the molten pool. The keyhole penetrating the molten pool helps to suppress the formation of keyhole-induced porosity inside of the molten pool. Therefore, a technical criterion for optimizing the combination of welding speed and laser power is proposed under the premise of full penetration welds generation: adjusting the time ratio of the keyhole periodically penetrating the molten pool to comprehensively suppress the pores inside the weld and the spatter on the back side.To suppress the formation of porosity defects inside the nickel-based high-temperature supperalloys weld, the laser beam oscillating method should be taken. and comprehensively optimize The process parameters such as the oscillating frequency and the oscillating amplitude should also be optimized comprehensively. High-quality full penetration laser welding are achieved by matching appropriate laser power and ensuring the stable welding of medium and thick plates progressing in keyhole mode.The welding parameters have an obvious influence on the microstructure and mechanical properties of Inconel 617 laser welding joints. Under the condition of high heat input, the grain size in the middle of the weld fusion zone is coarse, and the grain orientation is disordered. The secondary dendrite arm spacing in the middle of the weld is large. The carbide particle size between the dendrites is coarse, and the solidification microsegregation of Mo and Cr alloy elements is serious, resulting in weakness of the weld strength.The laser welding quality control technology of nickel-based superalloys obtained through the research work of the thesis has been applied in the field of aerospace manufacturing.