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Void Populations in Y2O3-Stabilized ZrO2 Coatings Deposited by High Velocity Oxy-Fuel (HVOF) Thermal Spray 
Tabbetha A. Dobbins, Andrew J. Allen, Jan Ilavsky, Gabrielle G. Long

National Institute for Standards and Technology (NIST)

Materials Science and Engineering Laboratory, Ceramics Division

Gaithersburg, MD20899

Anand Kulkarni, Herbert H. Herman

State University of New York at Stony Brook

Materials Science and Engineering Department

Stony Brook, NY 11790

Yttria-stabilized zirconia (YSZ) thermal barrier coatings (TBCs) are used to protect turbine rotor and blade components in aircraft and land-based engines from operational temperatures (exceeding 1200 oC).  Traditionally, those coatings are deposited using air plasma spray (APS) or electron beam physical vapor deposition (EB-PVD).  High Velocity Oxy-Fuel (HVOF) thermal spray (Figure 1) offers competing technology for TBC deposition.  The high velocity jet is expected to provide a modified pore microstructure due to the high impact velocity of the sprayed particles.  The present research examines anisotropic void microstructures in HVOF deposited thermal barrier coatings with comparison to APS and EB-PVD coatings using effective pinhole-collimated ultrasmall-angle x-ray scattering (USAXS) (Figure 2).  Small angle scattering intensity versus wave vector data were generated for coating cross-sections.  The coatings were oriented to several azimuthal angles (between 0o and 180o sample rotation) and the results were represented in polar configuration at constant wave vector.  The contrasting void microstructures in ceramic thermal barrier coatings deposited by HVOF and those in coatings deposited by other techniques will be discussed.  The goal of the present study is to develop an understanding of the relationship between processing and microstructure so that coating techniques and process parameters can be optimized for specific thermal barrier coating applications.