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

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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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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