Journal of Materials Science

, Volume 24, Issue 10, pp 3511–3520 | Cite as

Failure processes within ceramic coatings at high temperatures

  • Christopher C. Berndt
Review

Abstract

Plasma sprayed coatings have a complex structure which is produced by the overlaying of many molten or semi-molten particles in the diameter range of 20 to 120 µm. There is a need to characterize the failure behaviour of coatings and this has been carried out by using acoustic emission (AE) methodology.

Coatings of NiCrAIY bond coat with a zirconia-12 wt% yttria overlay were applied to discshaped specimens of U-700 alloy. A waveguide of 1 mm diameter platinum was TIG welded to the specimen and allowed it to be suspended in a tubular furnace. The specimen was thermally cycled to 1150° C and the AE monitored.

One method of examining the AE is from the viewpoint of the accumulative count data. It is also convenient to establish the temperatures for “initial” AE and “significant” AE (i.e., the temperature at which 100 counts is exceeded) so that coatings may be compared. Several other analyses have been carried out with the aim of establishing parameters which are related to the crack size and crack population. These studies have been used to postulate types of cracking mechanisms which may occur in plasma sprayed coatings during thermal cycling.

It is shown that microcracking gave rise to a large amount of AE. However, this coating still survived more thermal cycles than a coating which exhibited macrocracking events. Data of this nature will be presented and the results discussed.

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. 1.
    I. A. FISHER,Int. Met. Rev. 17 (1972) 117–129.Google Scholar
  2. 2.
    D. A. GERDEMAN and N. L. HECHT, “Arc Plasma Technology in Materials Science”, (Springer, New York, 1972).Google Scholar
  3. 3.
    R. A. MILLER and C. E. LOWELL,Thin Solid Films 95 (1982) 265–273.CrossRefGoogle Scholar
  4. 4.
    G. C. CHANG and W. PHUCHAROEN, in Thermal Barrier Coatings Workshop, May 21–22, 1985, (NASA-Lewis Research Center, Cleveland, Ohio, 1985) pp. 116–126.Google Scholar
  5. 5.
    J. R. MATTHEWS, “Acoustic Emission”, (Gordon and Breach, New York, 1983).Google Scholar
  6. 6.
    R. G. LIPTAI, D. O. HARRIS and C. A. TATRO, ASTM STP505, (American Society for Testing and Materials, Philadelphia, 1972).Google Scholar
  7. 7.
    R. E. GREEN, Jr, in Symposium proceedings of “Novel NDE Methods for Materials”, (Metallurgical Society of the AIME, Warrendale, Pennsylvania, 1983) pp. 131–139.Google Scholar
  8. 8.
    T. F. DROUILLARD, “Acoustic Emission: A Bibliography with Abstracts”, (Plenum, New York, 1979).Google Scholar
  9. 9.
    H. N. G. WADLEY, C. B. SCRUBY and J. H. SPEAKE,Int. Met. Rev. 25 (1980) 41–64.Google Scholar
  10. 10.
    R. W. HARRIS and B. R. A. WOOD,Metals Forum 5 (1982) 210–215.Google Scholar
  11. 11.
    D. ALMOND, M. MOGHISHI and H. REITER,Thin Solid Films 108 (1983) 439–447.CrossRefGoogle Scholar
  12. 12.
    N. RAVI SHANKARet al., Amer. Ceram. Soc. Bull. 62 (1983) 614–619.Google Scholar
  13. 13.
    C. C. BERNDT,ASME J. Eng. for Gas Turbines 107 (1985) 142–146.Google Scholar
  14. 14.
    C. C. BERNDT and H. HERMAN,Thin Solid Films 108 (1983) 427–437.CrossRefGoogle Scholar
  15. 15.
    C. C. BERNDT and R. A. MILLER, —ibid.119 (1984) 173–184.CrossRefGoogle Scholar
  16. 16.
    S. STECURA, Effects of Plasma Spray Parameters on Two-Layer Thermal Barrier Coating System Life”, NASA TM81724, March 1981.Google Scholar

Copyright information

© Chapman and Hall Ltd. 1989

Authors and Affiliations

  • Christopher C. Berndt
    • 1
  1. 1.Department of Materials EngineeringMonash UniversityClaytonAustralia

Personalised recommendations