针对传统工艺难以制备口径大于1.2m的整块反射镜的问题,提出了反应连接制备大口径RB-SiC反射镜的工艺。该工艺在素坯阶段实现连接,一次反应烧结完成坯体的致密化和镜体的连接。采用该工艺制备了230mm口径的RB-SiC反射镜,并使用FSGJ-2光学数控机床对反射镜进行了研磨、粗抛光和精抛光加工,其镜面面形精度RMS值达到了λ/50(λ=632.8nm)。在环境温度(20±3)℃检测了连接反射镜,其面形变化RMS值小于λ/300,热循环试验前后连接反射镜面形没有明显变化;连接镜体表面在焊缝处粗糙度Ra〈3.3nm,连接层与基体的显微结构基本相似,热性能相匹配。研究结果表明,用新型反应连接技术制成的RB-SiC反射镜可以满足空间光学应用要求。
As the aperture for a monolithic mirror was limited in 1.2 m by traditional technologies, a new reaction-formed joint technology for RB-SiC was proposed. With the proprosed technology, the SiC mirror was joined in the green body process, and the green body densification and the joint of mir- ror were finished in the same sintering process. A 230 mm diameter RB-SiC mirror was fabricated by this technology. After milling and polishing finely with the FSJG-2 facility, the figure error of the mirror surface is less than λ/50(λ= 632.8 nm) . The mirror was tested in the temperature range of (20±3) ℃, and the tested results show that the change of the figure error of the mirror surface is less than 2/300, and the mirror surface figure is not changed obviously after the thermal cycle test. More- over, the roughness of the surface near the joint line is 3.3 nm, and its microstructure is similar tothat of the RB-SiC ceramic. The thermal property of welding line is matching with that of RB-SiC ce- ramic. Obtained results demonstrate that the reaction-formed joint technology for the RB-SiC mirror satisfies the need of the large aperture mirror used in space optics.