Advertisement

Metallurgical and Materials Transactions A

, Volume 25, Issue 7, pp 1525–1533 | Cite as

Modeling solidification of turbine blades using theoretical phase relationships

  • Shuang-Lin Chen
  • W. Oldfield
  • Y. Austin Chang
  • M. K. Thomas
Solidification

Abstract

The solidification of hot-stage turbine blades made from René N4 nickel-base superalloy has been modeled to show the morphology of porosity and the local changes in solute concentration. The key task of the present study was the calculation of the solid-liquid phase equilibria of this 9-component nickel-base superalloy from the thermodynamic values of these phases. The Gibbs energies of the solid and liquid phases were obtained from those of the 36 binaries using the Muggianu and Kohler methods of extrapolation. The phase equilibrium data were then used to compute the change in fraction solid with temperature, initially using the complete mixing approximation (Scheil equation). The predicted freezing range was somewhat longer than measured. A modified Scheil equation was derived assuming incomplete mixing. Assuming 60 pct mixing of the solute, the calculated freezing range agreed with experiments. Fraction solid temperature allowed the detailed morphology of the“mushy”zone to be predicted. Using measured dendrite spacings and assuming the crystals to grow in a cubic array, the shape of the crystals and, consequently, the size of the liquid channels were predicted as a function of position. Hence, computation of the rate of fluid flow in the channels (from the known changes of temperature with time) allowed the pore morphology to be inferred.

Keywords

Gibbs Energy Material Transaction Mushy Zone Excess Gibbs Energy Freezing Range 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. 1.
    W. Oldfield and A.F. Mahon: inLife Assessment and Repair Technology for Combustion Turbine Hot Section Components, EPRI GS-7031, R. Viswanathan and J.M. Allen, eds., ASM INTERNATIONAL, Metals Park, OH, and Electric Power Research Institute, 1990.Google Scholar
  2. 2.
    W. Oldfield and F.M. Oldfield:Metall. Trans. A, 1993, vol. 24A, pp. 2313–19.Google Scholar
  3. 3.
    K.-C. Chou and Y.A. Chang:Ber. Bunsenges. Phys. Chem., 1989, vol. 93, pp. 735–41.Google Scholar
  4. 4.
    L.S. Darken and R.W. Gurry:Physical Chemistry of Metals, McGraw-Hill, New York, NY, 1953.Google Scholar
  5. 5.
    C. Wagner:Thermodynamics of Alloys, Addison-Wesley, Cambridge, MA, 1952.Google Scholar
  6. 6.
    L. Kaufman and H. Bernstein:Computer Calculation of Phase Diagrams, Academic Press, New York, NY, 1970.Google Scholar
  7. 7.
    Y.-Y. Chuang and Y.A. Chang:Metall. Trans. A, 1987, vol. 18A, pp. 733–45.Google Scholar
  8. 8.
    L. Kaufman and H. Nesor:Z. Metallkd., 1973, vol. 64, pp. 249–257.Google Scholar
  9. 9.
    L. Kaufman and H. Nesor:CALPHAD, 1978, vol. 2, pp. 55–80.CrossRefGoogle Scholar
  10. 10.
    L. Kaufman and H. Nesor:CALPHAD, 1978, vol. 2, pp. 81–108.CrossRefGoogle Scholar
  11. 11.
    L. Kaufman and H. Nesor:CALPHAD, 1978, vol. 2, pp. 325–48.CrossRefGoogle Scholar
  12. 12.
    S.-L. Chen, K.-C. Hsieh, and Y.A. Chang: University of Wisconsin, Madison, WI, unpublished research, 1991.Google Scholar
  13. 13.
    U. Kattner: National Institute of Science and Technology, Gaithersburg, MD, private communication, 1991.Google Scholar
  14. 14.
    W. Oldfield:J. Test. Eval., 1979, vol. 7, pp. 326–33.Google Scholar
  15. 15.
    W.H. Press, B.P. Flannery, S.A. Teukolsky, and W.T. Vetterling:Numerical Recipes, Cambridge University Press, Cambridge, United Kingdom, 1989.Google Scholar
  16. 16.
    E.W. Ross and R.G. Carlson:“Manufacturing Technology for Advanced Propulsion Materials. Phase IX — Advanced Turbine Airfoil Casting Technology. Task 2: Casting Simulation,”Contract No. F33615-85-C-5014, GE Aircraft Engines, Engineering Materials Technology Laboratories, 7th Interim Technical Report, Feb.-July 1989.Google Scholar
  17. 17.
    R.G. Carlson: “Manufacturing Technology for Advanced Propulsion Materials. Phase IX — Advanced Turbine Airfoil Casting Technology. Task 2: Casting Simulation,”Contract No. F33615-85-C-5014, GE Aircraft Engines, Engineering Materials Technology Laboratories, 9th Interim Technical Report, Feb.-July 1990.Google Scholar

Copyright information

© The Minerals, Metals and Materials Society, and ASM International 1994

Authors and Affiliations

  • Shuang-Lin Chen
    • 1
  • W. Oldfield
    • 2
  • Y. Austin Chang
    • 1
  • M. K. Thomas
    • 3
  1. 1.Department of Materials Science and EngineeringUniversity of WisconsinMadison
  2. 2.Materials and Computer Simulation Inc.Hertford
  3. 3.Naval Air Warfare CenterWarminster

Personalised recommendations