Mechanical Behavior of Air Plasma-Sprayed YSZ Functionally Graded Mullite Coatings Investigated via Instrumented Indentation


Yttria-stabilized zirconia (YSZ)-mullite multilayer architectures with compositional grading between the bond coat and YSZ top coat are envisioned as solutions to ease their coefficient of thermal expansion mismatch induced stress. In this work, two different types of mullite powder (spray-dried and freeze-granulated) and a mullite-YSZ 75/25 vol.% mixture spray-dried powder were employed. Using instrumented indentation with loads between 10 and 500 mN, the role of the powder characteristics on the mechanical behavior of air plasma-sprayed mullite bond coats deposited on SiC substrates was investigated. Hardness (H) and elastic modulus (E) were measured for the as-sprayed coatings and for coatings heat-treated at 1300 °C, in water vapor environment, for periods up to 500 h. Both H and E values of the coatings are found to be highly dependent on the size distribution of the starting powders. It is aimed the fabrication of an efficient and cost-effective EBC prototype based on YSZ compositionally graded mullite.

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  1. 1.

    K.N. Lee, Current Status of Environmental Barrier Coatings for Si-Based Ceramics, Surf. Coat. Technol., 2000, 133-134, p 1-7

    CAS  Article  Google Scholar 

  2. 2.

    S. Latzel, R. Vaßen, and D. Stöver, New Environmental Barrier Coating System on Carbon-Fiber Reinforced Silicon Carbide Composites, J. Therm. Spray Technol., 2005, 14, p 268-272

    CAS  Article  Google Scholar 

  3. 3.

    K.N. Lee, D.S. Fox, and N.P. Bansal, Rare Earth Silicate Environmental Barrier Coatings for SiC/SiC Composites and Si3N4 Ceramics, J. Eur. Ceram. Soc., 2005, 25, p 1705-1715

    CAS  Article  Google Scholar 

  4. 4.

    H. Schneider, J. Schreuer, and B. Hildmann, Structure and Properties of Mullite: A Review, J. Eur. Ceram. Soc., 2008, 28, p 329-344

    CAS  Article  Google Scholar 

  5. 5.

    N.S. Jacobson, Corrosion of Silicon-Based Ceramics in Combustion Environments, J. Am. Ceram. Soc., 1993, 76, p 3-28

    CAS  Article  Google Scholar 

  6. 6.

    N.S. Jacobson, D.S. Fox, J.S. Smialek, E.J. Opila, C. Dellacorte, and K.N. Lee, Performance of Ceramics in Severe Environments, ASM Handbook, Vol. 13B Corrosion Materials, p 565

  7. 7.

    U. Schulz, M. Peters, Fr.-W. Bachb, and G. Tegeder, Graded Coatings for Thermal, Wear and Corrosion Barriers, Mater. Sci. Eng. A, 2003, 362, p 61-80

    Article  Google Scholar 

  8. 8.

    T.W. Murray, O. Balogun, T.L. Steen, S.N. Basu, and V.K. Sarin, Inspection of Compositionally Graded Mullite Coatings Using Laser Based Ultrasonics, Int. J. Refract. Met. Hard Mater., 2005, 23, p 322-329

    CAS  Article  Google Scholar 

  9. 9.

    C. Cano, E. Garcia, A.L. Fernandes, M.I. Osendi, and P. Miranzo, Mullite/ZrO2 Coatings Produced by Flame Spraying, J. Eur. Ceram. Soc., 2008, 28, p 2191-2197

    CAS  Article  Google Scholar 

  10. 10.

    P.K. Rohatgi, N. Gupta, and S. Alaraj, Thermal Expansion of Aluminum-Fly Ash Cenosphere Composites Synthesized by Pressure Infiltration Technique, J. Compos. Mater., 2006, 40(13), p 1163-1174

    CAS  Article  Google Scholar 

  11. 11.

    R. Asthana, A. Kumar, and N.B. Dahotre, Materials Processing and Manufacturing Science, Elsevier, Amsterdam, 2006

    Google Scholar 

  12. 12.

    E. Garcia, J. Mesquita-Guimarães, P. Miranzo, and M.I. Osendi, Procedure for Obtaining Ceramic Feedstock for Thermal Spraying Applications, Patent 2009, ICV-CSIC, Ref. ES1641.581, Spain

  13. 13.

    W.C. Oliver and G.M. Pharr, Measurement of Hardness and Elastic Modulus by Instrumented Indentation: Advances in Understanding and Refinements to Methodology, J. Mater. Res., 2004, 19(1), p 3-20

    CAS  Article  Google Scholar 

  14. 14.

    R. McPherson, A Review of Microstructure and Properties of Plasma sprayed Ceramic Coatings, Surf. Coat. Technol., 1989, 39-40, p 173-181

    CAS  Article  Google Scholar 

  15. 15.

    E. Garcia, J. Mesquita-Guimarães, P. Miranzo, M.I. Osendi, C.V. Cojocaru, Y. Wang, C. Moreau, and R.S. Lima, Phase Composition and Microstructural Responses of Crystalline Mullite/YSZ Coating Under Water Vapor Environments, Thermal Spray: Global Solution for Future Application (ITSC 2010 Proceedings), DVS-Verlag GmbH, Dusseldorf, Germany, 2010, PDF Format (CD)

  16. 16.

    A.A. Elmustafaa and D.S. Stone, Nanoindentation and the Indentation Size Effect: Kinetics of Deformation and Strain Gradient Plasticity, J. Mech. Phys. Solids, 2003, 51, p 357-381

    Article  Google Scholar 

  17. 17.

    B.-K. Jang, Influence of Low Indentation Load on Young’s Modulus and Hardness of 4 mol% Y2O3-ZrO2 by Nanoindentation, J. Alloy Compd., 2006, 426, p 312-315

    CAS  Article  Google Scholar 

  18. 18.

    C.V. Cojocaru, S. Kruger, C. Moreau, and R.S. Lima, Mechanical Properties and Behaviour of BSAS/Mullite-Based Environmental Barrier Coatings Exposed to High Temperature in Water Vapour Environment, Thermal Spray: Global Solution for Future Application (ITSC 2010 Proceedings), DVS-Verlag GmbH, Dusseldorf, Germany, 2010, PDF Format (CD)

  19. 19.

    R.S. Lima and B.R. Marple, Toward Highly Sintering-Resistant Nanostructured ZrO2-7 wt.% Y2O3 Coatings for TBC Applications by Employing Differential Sintering, J. Therm. Spray Technol., 2008, 17, p 846-852

    CAS  Article  Google Scholar 

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The NRC team of authors acknowledges valuable technical support from the technical officers of the Surface Technology Group for samples production, metallographic preparation, and SEM analysis. This work has been supported by NRC-CSIC program (project 2007CA003).

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Correspondence to C. V. Cojocaru.

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This article is an invited paper selected from presentations at the 2010 International Thermal Spray Conference and has been expanded from the original presentation. It is simultaneously published in Thermal Spray: Global Solutions for Future Applications, Proceedings of the 2010 International Thermal Spray Conference, Singapore, May 3-5, 2010, Basil R. Marple, Arvind Agarwal, Margaret M. Hyland, Yuk-Chiu Lau, Chang-Jiu Li, Rogerio S. Lima, and Ghislain Montavon, Ed., ASM International, Materials Park, OH, 2011.

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Cojocaru, C.V., Wang, Y., Moreau, C. et al. Mechanical Behavior of Air Plasma-Sprayed YSZ Functionally Graded Mullite Coatings Investigated via Instrumented Indentation. J Therm Spray Tech 20, 100–107 (2011).

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  • elastic modulus
  • environmental barrier coatings
  • heat-treatment
  • mullite
  • water vapor
  • YSZ