基于离散沉积原理的大口径碳化硅反射镜纳米复合加工机理与方法研究

According to the rigid technical requirements, ultra-high surface figure accuracy and high smooth surface, of China Space Station Telescope, CSST, which is National major scientific technological infrastructure. This project plans to carry out the research on the composite manufacturing technology of large caliber silicon carbide mirror based on discrete-stacking principle. In view of the difficulty of improving the accuracy of surface figuring due to the edge effect and the lack of control of mid-high frequency errors for traditional reduction machining method. In this project, the high precision and high efficiency manufacturing of large caliber SiC mirror is put forward by using the composite machining technology of adding and reducing material: for the edge collapse or local depression, the local deposition method is used to fill the mirror, Substitute for increase and subtract, avoiding the removal of full aperture material in traditional material reduction processing; In order to solve the problem of mid-high frequency errors, the technology of adding material is used to smooth the uneven area of the surface, to reduce the processing difficulty of mid-high frequency errors, and to realize the super smooth machining combined with high certainty reduction machining. The project intends to carry out the research on the deposition mechanism of local material addition under complex constraint conditions, the forming process of local deposition growth function, and the composite machining strategy of adding and reducing material under complex surface morphology, and so on. Finally, the basic theory and key technology of high-precision composite machining for 2m-order spatial SiC mirror are formed, which lays the theoretical and technical foundation for the high-precision and high-efficiency manufacturing of space astronomical telescopes.

针对国家重大科技基础设施“空间站巡天望远镜”对大口径碳化硅空间反射镜超高面形精度、高平滑面形质量的技术需求，项目拟开展基于离散沉积原理的大口径碳化硅反射镜复合制造技术研究。针对传统减材加工方法对边缘效应和中高频控制不足导致面形精度提升困难的问题，项目提出采用增减材复合加工技术实现大口径SiC反射镜的高精度高效制造：针对边缘塌边或者局部凹陷，使用局域沉积的方式进行填补，以增代减，避免了传统减材加工中全口径的材料去除；针对中高频问题，增减结合，使用增材技术平滑表面凹凸不平区域，结合高确定性减材加工实现超平滑加工。项目拟开展复杂边界条件下局域增材的沉积机理、局域沉积生长函数的应变耦合模型及复杂面形形貌下增减材复合加工策略等研究，最终形成面向大口径空间SiC反射镜的高精度复合加工理论，为空间天文望远镜的高精度高效制造奠定技术基础。

针对国家重大科技基础设施“空间站巡天望远镜”对大口径碳化硅空间反射镜超高面形精度、高平滑面形质量的技术需求，项目开展了基于离散沉积原理的大口径碳化硅反射镜复合制造技术研究。针对传统减材加工方法对边缘效应和中高频控制不足导致面形精度提升困难的问题，项目提出采用增减材复合加工技术实现大口径SiC反射镜的高精度高效制造，进行了局域增材沉积机理、沉积生长函数模型、局域沉积应力模型、膜层沉积过渡区域表面结合性能、增减材复合加工策略等方面的研究。. 对于反射镜局部凹陷和边缘塌边工况，使用局域增材沉积方式进行填充，以增代减，大幅降低了传统减材加工中全口径材料去除的时间，极大提高了加工效率。对于反射镜表面中高频问题，使用辅助材料沉积牺牲层的方法削弱反射镜表面峰谷分布，实现面形误差的全频段修正。对于反射镜粗糙度提升方面，基于倾斜角度入射离子溅射平滑效应进行改善。. 完成了不同形状、尺寸、作用距离孔阑工况下局域增材沉积函数的仿真分析和实验验证，为增减材非序列复合制造技术提供了序列丰富的加工函数库。完成了增减材非序列复合制造技术大口径SiC反射镜的过程模拟、结果预测模型和计算机应用软件研发，为大口径SiC反射镜高效高精度制造提供了良好的技术基础。. 完成了Φ200mm口径SiC实验样件的加工，面形精度检测结果为3.94nm RMS，Slope-rms为0.45μrad@2mm，满足项目计划中面形精度<5nm RMS，Slope-rms＜1.0μrad@2mm的要求，验证了基于离散沉积原理的大口径碳化硅反射镜复合制造技术的工程可行性，为大口径空间碳化硅反射镜的研制技术提供了新思路新方案，为大口径光学成像系统在天文探索、遥感观测等方向奠定了重要基础。