• Reed, Roger C.
• Gebelin, Jean Christophe
• Panwisawas, Chinnapat
• Broomfield, Robert W.
• Warnken, Nils

Abstract

<p>During the manufacture of turbine blades from single crystal nickel-based superalloys by investment casting, recrystallisation can occur during solution heat treatment. The introduction of grain boundaries into a single crystal component is potentially detrimental to performance, and therefore manufacturing processes and/or component geometries should be chosen to prevent their occurrence. In this work, numerical models have been designed to enable a predictive capability for the factors influencing recrystallisation to be constructed. The root cause is plasticity on the microscale caused by differential thermal contraction of metal, mould and core; when the plastic deformation is sufficient, recrystallisation can take place subsequently. The models take various forms. First, one-dimensional models based upon static equilibrium have been produced - our calculations indicate that plastic strain is likely to take place in two temperature regimes: by creep between 1150°C and 1000°C and by tensile (time-independent) strain below 650°C. The idea of a strain-based criterion for recrystallisation is then proposed. Second, more sophisticated threedimensional calculations based upon the finite element method are carried out. Our predictions are compared critically with experimental information.</p>

Topics

• impedance spectroscopy
• polymer
• single crystal
• grain
• nickel
• plasticity
• creep
• one-dimensional
• solidification
• superalloy
• investment casting