烧结温度对3D打印硅基陶瓷型芯表面形貌及粗糙度的影响

单晶高温合金空心叶片是航空发动机的重要部件, 其内腔结构是采用陶瓷型芯制备的。随着航空发动机推重比提高, 型芯结构越来越复杂, 传统制备工艺受限, 光固化3D打印陶瓷型芯技术为复杂结构型芯的制备提供了一种可行方案。为了改善光固化3D打印陶瓷型芯因台阶效应导致的表面粗糙度较大的问题, 本研究利用固含量体积分数63%的硅基型芯浆料进行光固化3D打印型芯, 并在1100~1300 ℃对型芯素坯进行烧结, 对烧成的硅基陶瓷型芯的微观结构、元素分布、相组成、型芯打印面和打印堆积方向的表面形貌和粗糙度进行分析。研究发现型芯打印面平整, 无明显表面缺陷, 1100、1200和1300 ℃烧结型芯的打印面粗糙度分别为1.83、1.24和1.44 μm; 片层堆积方向的表面有片层结构特征, 片层间出现微裂纹, 1200 ℃以上烧结的型芯表面粗糙度达到空心叶片使用要求(R_a≤2.0 μm)。结果表明不同烧结温度会改变型芯烧结过程中的液相含量、莫来石生成量、莫来石生成形态和颗粒间玻璃相的分布, 从而对光固化3D打印硅基陶瓷型芯的表面粗糙度产生明显影响。光固化3D打印陶瓷型芯技术结合烧结工艺能制备出满足先进空心叶片用硅基陶瓷型芯表面要求的粗糙度。

Effect of Sintering Temperature on Surface Morphology and Roughness of 3D-printed Silicon Ceramic Cores

Single crystal superalloy hollow blade is an important part of aero-engine, and its inner cavity structure is prepared by ceramic core. With the increase of thrust-weight ratio of aero-engine, the core structure is more and more complex. Traditional preparation technology is difficult to meet the requirements of complex core preparation. Stereolithography 3D printing of ceramic cores provides a feasible scheme for the preparation of complex cores. In order to improve the surface roughness of stereolithography 3D printed ceramic cores caused by step effect, this study used silicon-based core paste with solid content of 63% (in volume), and the cores of the green bodies were sintered at 1100 ℃ to 1300 ℃. Microstructure, element distribution, phase composition, surface morphology, and roughness of the silicon-based ceramic core were analyzed. It is found that printed surface of the core is smooth without obvious surface defects. Roughness of the printed surfaces of the sintered cores at 1100, 1200 and 1300 ℃ are 1.83, 1.24 and 1.44 μm, respectively. Their surface of lamellar stacking direction has lamellar structure characteristics, and microcracks appear between lamellar, and surface roughness of core sintered above 1200 ℃ meets the requirements (R_a≤2.0 μm) of hollow blade. Sintering temperatures affect the liquid content, mullite production, mullite formation morphology, and glass phase distribution of cores during the sintering process, and the surface roughness of stereolithography 3D-printed silicon ceramic cores is positively affected. Stereolithography 3D printing ceramic core technology combined with sintering process can produce a silicon-based ceramic core which surface roughness meets the requirements of an advanced hollow blade.