Prediction of recrystallization in investment cast single-crystal superalloys

Research output: Contribution to journalArticlepeer-review

Authors

  • Harshal Mathur
  • Duncan Putman
  • Catherine M F Rae

External organisations

  • University of Cambridge
  • Rolls Royce PLC

Abstract

Modelling and targeted experimentation are used to quantify the processing conditions which cause recrystallization in a single-crystal superalloy. The plasticity needed is traced to the differential thermal contractions of the metal and its ceramic mould during processing. For typical cooling rates, the plasticity causing recrystallization is induced above 1000 °C, thus over a temperature interval of approximately 300 °C after solidification is complete. The total accumulated plastic strain needed for recrystallization is estimated to be in the range of 2-3%. Modelling is used to rationalize the influence of mould thickness, stress concentration factor and geometry on the induced plasticity. Negligible plastic strains were predicted in a solid casting with no stress concentration features, as found experimentally. However, recrystallization occurred in thin-walled sections, particularly beneath shroud-like features due to the plasticity induced there. The model provides the foundation for a systems-based approach which enables recrystallization to be predicted and thus avoided in new designs of turbine blade aerofoil.

Details

Original languageEnglish
Pages (from-to)51-66
Number of pages16
JournalActa Materialia
Volume61
Issue number1
Publication statusPublished - Jan 2013

Keywords

  • Investment casting, Mechanical deformation, Solidification, Superalloys