10. Damage Process of Thermal Barrier Coating Subjected to Thermal Cycling Under High Heat Flux

  1. Dongming Zhu and
  2. Kevin Plucknett
  1. Mitsutoshi Okada1,
  2. Tohru Hisamatsu1,
  3. Ryuichi Ohtani1,
  4. Hideyuki Arikawa2 and
  5. Yoshitaka Kojima2

Published Online: 26 MAR 2008

DOI: 10.1002/9780470291238.ch10

Advances in Ceramic Coatings and Ceramic-Metal Systems: Ceramic Engineering and Science Proceedings, Volume 26, Number 3

Advances in Ceramic Coatings and Ceramic-Metal Systems: Ceramic Engineering and Science Proceedings, Volume 26, Number 3

How to Cite

Okada, M., Hisamatsu, T., Ohtani, R., Arikawa, H. and Kojima, Y. (2008) Damage Process of Thermal Barrier Coating Subjected to Thermal Cycling Under High Heat Flux, in Advances in Ceramic Coatings and Ceramic-Metal Systems: Ceramic Engineering and Science Proceedings, Volume 26, Number 3 (eds D. Zhu and K. Plucknett), John Wiley & Sons, Inc., Hoboken, NJ, USA. doi: 10.1002/9780470291238.ch10

Author Information

  1. 1

    Central Research Institute of Electric Power Industry Yokosuka, 240-0196, Japan

  2. 2

    Hitachi Research Laboratory, Hitachi, Ltd. Hitachi, 317-8511, Japan

Publication History

  1. Published Online: 26 MAR 2008
  2. Published Print: 1 JAN 2005

ISBN Information

Print ISBN: 9781574982336

Online ISBN: 9780470291238

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Keywords:

  • apparatus;
  • impurities;
  • ceramic;
  • turbines;
  • thermocouples

Summary

In order to develop an evaluation method for resistance to thermal cycling of thermal barrier coatings (TBCs) for gas turbines, thermal cycle tests were performed by means of a high heat-flux heating apparatus, where the surface of TBC specimens was heated cyclically by plasma gas flow and the other surface was cooled by water. This experiment nearly simulated a thermal condition in gas turbines. The experimental observation clarified the damage processes in TBC systems under high heat flux. At first, cracks were initiated in the direction of the coating thickness (vertical cracks). When they reached at the vicinity of the boundary between a top coat and a bond coat, the cracks growing along the boundary (transverse cracks) were initiated. The transverse cracks coalesced each other, to lead the top coat to delamination. After the thermal cycle test, the porosity of the top coat decreased due to sintering. The tensile stress increased due to the top coat sintering, as well as the thermal fatigue due to thermal cycling, promotes the initiation and growth of vertical cracks. In the thermal cycle tests on a more porous TBC with lower content of impurities such as SiO2, the growth rate of vertical cracks was smaller and the coalescence of transverse cracks was less frequent than the denser TBC including more impurities. This results from the decrease in Young's modulus and thermal conductivity due to the porosity increase, the decrease in the impurity content, and the difference of sprayed particle shape.