航天用镍基高温合金及其激光增材制造研究现状

新型航天器用镍基高温合金部件呈现出复杂化、薄壁化、复合化、一体化的发展趋势，使得传统的铸造或锻造加工技术无法胜任。基于逐层堆积的激光增材制造(LAM)技术是实现这类复杂部件制备的理想解决方案，能够进一步赋予高温合金更高的价值，极大地推动航天装备的发展。首先介绍了航天领域常用的镍基高温合金种类，然后以研究最多的IN 718和IN 625合金为例，总结了镍基高温合金增材制造的研究现状:归纳了镍基高温合金增材制造工艺优化方法，表明增材制造综合加工图和实验设计方法是两种行之有效的方法;指出了增材制造镍基高温合金材料的微观组织特点，讨论了增材制造后续热处理对材料微观组织和力学性能的影响规律，表明增材制造技术极快速冷却的特点引起镍基高温合金材料内部存在普遍的局部微观偏析现象，导致常规热处理工艺不再是最优工艺;并通过5个典型的增材制造镍基高温合金航天构件案例展示了增材制造技术的优势。在此基础上，针对镍基高温合金增材制造过程中存在的关键科学问题和技术难题，展望了增材制造镍基高温合金未来的研究方向。

Research Status of Nickel-based Superalloy for Aerospace Field and Its Laser Additive Manufacturing Technology

Nickel-based superalloy components for new spacecraft exhibit a development trend of complexity, thin wall, combination, and integration. As a result, traditional processing technologies such as casting or forging are no more available. Laser additive manufacturing (LAM) technology based on layer-by-layer deposition becomes an ideal solution to realize the fabrication of such complex components, which can further endow superalloy with higher value and promote the development of aerospace equipment. Firstly, the nickel-based superalloy frequently used in the aerospace field was briefly introduced, and then the research status of nickel-based superalloy prepared by LAM was reviewed with IN 718 and IN 625 as examples. The optimization method of additive manufacturing process was summarized, indicating that comprehensive processing map of additive manufacturing and experimental design were two effective methods. The microstructure characteristics of nickel-based superalloy by LAM were pointed out, and the effect of LAM-post heat-treatment on the microstructure and mechanical properties was also discussed. The local microsegregation in nickel-based superalloy by LAM was ubiquitous, which was caused by the rapid cooling rate inherent in the LAM process. Therefore, the conventional heat treatment was no longer the optimal process due to microsegregation. The advantages of LAM technology were demonstrated through five typical cases of nickel-based superalloy aerospace components by LAM. Finally, some future research directions on LAM technology of nickel-base superalloy were put forward and prospected according to the key scientific and technical problems in nickel-based superalloy by LAM.