Fig. 1. Internal structure of turbine blades. (a) Development trend of turbine blade internal structure^[5]; (b) typical gas-cooled structure inside gas turbine blades^[6]

Fig. 2. Design of ceramic core/shell for superalloy airfoil^[9]. (a) Ceramic core for complex internal cooling passages; (b) cross-section of integrally cored ceramic mold; (c) profile of integrally cored ceramic mold

Fig. 3. Preparation of ceramic core/shell by SLS process

Fig. 4. Al₂O₃-SiO₂ ceramic parts prepared by SLS^[17]

Fig. 5. Surface morphology of alumina ceramic parts prepared by SLS. (a) Before debinding; (b) after debinding

Fig. 6. Two main process routes for preparation of ceramic core/shell by SLA process

Fig. 7. Effect of particle size distribution on segregation in layers of green body fabricated by SLA process^[66].(a) Regions representing segregation and no segregation in layers; (b) bimodal powder; (c) coarse powder

Fig. 8. Green bodies under different drying conditions^[44]. (a) Air drying; (b) freeze drying

Fig. 9. Ceramic shell/core fabricated by SLA＋gel casting^[77]. (a) CAD model of simplified ceramic impingement hole cores (CIHCs); (b) CIHCs prototype fabricated by SLA process; (c) CIHCs mold; (d) cross-section of double wall blade; (e) deformation of double-wall ceramic core from finite element simulation; (f) cross-section of fabricated metal double-wall blade

Fig. 10. Integrally cored ceramic mold for turbine airfoil with complex internal hollow structure^[9]. (a) Three-dimensional model; (b) green body; (c) sintered body without any cracks

Table 1. Typical properties of ceramic cores and shells prepared by conventional processes and laser additive manufacturing processes

Table 2. Characteristics of different laser additive manufacturing processes used for ceramic core/ shell manufacturing