烧结温度对氧化铝基陶瓷型壳显微组织及力学行为的影响

摘要

Selective laser sintering (SLS) was adopted to rapidly prepare silica-based ceramic shell for superalloy turbine blade, and combined with high-temperature sintering process to further improve the mechanical properties of ceramic shell. The effects of different sintering temperatures (1450~1600 ℃) on the flexural strength of alumina-based ceramic shells were investigated. The phase constitution and fracture morphology of alumina-based ceramic shell molds were analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results show that ceramic shell with excellent mechanical properties can be obtained by SLS+high-temperature sintering quickly and effectively. As sintering temperature increases from 1450 ℃ to 1600 ℃, flexural strength of ceramic shell at room temperature increases, and reaches 38.03 MPa at 1600 ℃. Columnar mullite phase is the main strengthening phase, with the increase of sintering temperature, the content of mullite phase in the shell increases, the content of quartz phase decreases, and the content of cristobalite phase increases first and then decreases. The crack propagation form changes from slow expansion to rapid expansion and causes transient fracture. The fracture changes from a tearing shape to a flush small section, and appear the intergranular and transgranular fracture mode, the crack is tended to expand to the mullite particles.%采用选择性激光烧结（selective laser sintering，SLS）快速制备高温合金叶片用氧化铝基陶瓷型壳初坯，并结合高温烧结（high-temperature sintering）进一步提高陶瓷型壳的力学性能。研究不同烧结温度（1450~1600 ℃）对氧化铝基陶瓷型壳的抗弯强度的影响，采用X射线衍射仪（XRD）、扫描电子显微镜（SEM）分析型壳的物相组成、断口微观形貌。结果表明：采用选择性激光烧结+高温烧结技术可快速高效地制备力学性能满足要求的陶瓷型壳，随着烧结温度从1450 ℃升高到1600 ℃，型壳的室温平均抗弯强度增大，并在1600 ℃时达到38.03 MPa；型壳的主要强化相为柱状莫来石相，且随烧结温度升高，型壳中莫来石相含量增加，石英相含量降低，方石英相含量先增加后有所降低；裂纹扩展形式从缓慢扩展转变为迅速扩展并引发瞬断，断口由撕裂状演变为平齐小断面，断裂方式由主要沿晶断裂向穿晶断裂转变，裂纹倾向于向晶内莫来石扩展。