Alumina-based ceramic mold with integral core and shell for hollow turbine blades fabricated by laser powder bed fusion

Abstract

Alumina-based ceramic molds are extensively applied in investment casting processes of hollow turbine blade due to their outstanding high-temperature chemical stability and creep resistance. Herein, laser powder bed fusion ( L -PBF) method was utilized to fabricate an alumina-based ceramic mold with integral core and shell (CMCS). The influences of the component contents in the composite powder on fluidity and packing density were comprehensivley studied, and the optimized formulation for the composite powder was consequently determined as 88 wt% mixed spherical alumina (coarse: fine = 9:1), 12 wt% epoxy resin E12, and 0.1 wt% fumed silica. The vacuum infiltration process was adopted to improve mechanical properties of alumina ceramic after the sintering, where the solid loading of ceramic slurry was investigated. The CMCS was divided into two parts for fabrication, i.e., the core&shell and the base with a spiral grain selector, which could facilitate convenient of cleaning residual powder due to enlarged openings. After the first infiltration and pre-sintering, the separated two parts were bonded by a ceramic binder and then underwent second infiltration and final-sintering to obtain a complete CMCS. The alumina-based ceramic fabricated through L -PBF and post-treatment possessed low sintering shrinkage (1.51–2.03%), adequate apparent porosity (30.82 ± 0.01%), and room-temperature strength (13.03 ± 2.90 MPa for unbonded specimen, 9.72 ± 1.34 MPa for bonded specimen). Strikingly, the subsequent casting experiment has proved that the method proposed in this paper is promising to fabricate superior alumina-based CMCSs.