Processing of a Single Crystal Casting for Heavy-Duty Gas Turbine Blades: Creep and Metal/Mould Reaction Behavior of Al2O3-SiO2 Shell Mould

Abstract

Al2O3-SiO2 moulds have been adopted successfully as shell moulds for a single crystal casting for jet engine blades. Heavy-duty gas turbine blades also have large dimensions and complex features comparable to those of jet engines. Then shell moulds should be subjected to similar severe service conditions when casting heavy-duty gas turbine blades. Creep behavior of 90mol%Al2O3+10mol%SiO2, which was manufactured through the lost wax process by using fused Al2O3 powder (average particle size, 15 μ m), was studied at temperatures of 1450 to 1550 °C. in four-point bending creep tests. Creep deflection rates were linearly proportional to stresses. The proposed creep mechanism was Al grain boundary diffusion at the interfacial regions between Al2O3 stucco powder. No severe metal/mould reaction appeared for the region adjacent to the interface between moulds and Ni base superalloys.