Effect of sintering temperature on microstructure and mechanical behavior of alumina-based ceramic shell by SLS

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.