Recent Developments in the Characterization of Extreme-Anisotropic Void Populations in Advanced Thermal Coatings TA Dobbins 1, AJ Allen 1, J Ilavsky 1,2,D Hass 3, H Wadley 3, A Kulkarni 4, J Almer 5, F DeCarlo 5 1. Ceramics Division, Materials Science and Engineering Laboratory, NIST, Gaithersburg, MD Dept. of Chemical Engineering, Purdue University, West Lafayette, IN Intelligent Processing of Materials Laboratory, University of Virginia, Charlottesville, VA NSF Center for Thermal Spray Research, SUNY Stony Brook, Stony Brook, NY Argonne National Laboratory, Advanced Photon Source - XOR Acknowledgments The UNICAT facility at the Advanced Photon Source (APS) is supported by the University of Illinois at Urbana-Champaign, Materials Research Laboratory (U.S. Department of Energy (DoE), the State of Illinois IBHE-HECA, and the National Science Foundation), the Oak Ridge National Laboratory (U.S. DoE), the National Institute of Standards and Technology (U.S. Department of Commerce) and UOP LLC. The SRI-CAT facility at the APS is supported by Argonne National Laboratory. The authors would like to thank Dr. Francesco DeCarlo for his kind assistance in use of the facility. Use of APS is supported by the U.S. DoE, Basic Energy Sciences, Office of Science, under Contract No. W ENG-38. The NIST Center for Neutron Research is supported by the National Science Foundation and the U.S. Department of Commerce. Other support from Drexel University’s Center for Plasma Processing of Materials, the National Research Council and the Office of Naval Research is graciously acknowledged. The authors wish to thank Mr. A. Kulkarni, graduate researcher at SUNY Stonybrook, for useful discussions. 4/30/03 Void microstructures in industrial thermal barrier coatings dictate properties and performance. These physical vapor deposited coatings are formed with micrometer-scale voids between PVD columns and nm-scale voids within PVD columns. Third generation x-ray synchrotron microstructure characterization methods are being used to yield state-of-the-art measurements at high spatial resolutions to provide quantitative parameters about column growth texture and void sizes, size distribution, orientation distribution, and connectivity. These parameters may be used as input for future microstructure-based predictive models or for process control. Motivation Characterized by HESAXS and WAXD using 5  m by 50  m beam size, electron beam directed vapor deposited (EB-DVD) coatings show transformation from equiaxed growth (continuous rings) to textured growth (uneven rings). Small angle scattering shows ‘off-axis’ voids more prominent farther from substrate. Summary Void microstructures in physical vapor deposited coatings have been characterized using 2-D collimated Bonse-Hart USAXS, High energy (80keV) small- angle x-ray scattering and x-ray computed microtomography (XMT), resulting in parameters which can be used for studies of microstructure growth and in- service changes. References 1.J. Ilavsky, A.J. Allen, G.G. Long, P.R. Jemian, Review of Scientific Instruments 73[3] 1660 (2002). 2.Dobbins T.A., Allen A.J., Ilavsky J., Kulkarni A., Herman H., “Current Developments in the Characterization of the Anisotropic Void Populations in Thermal Barrier Coatings Using Small Angle X-ray Scattering”, Ceramic Engineering and Science Proceedings 24[3/4], Figure 1. Schematic illustrates void microstructures in PVD coatings.  m-scale voids between PVD columns impart strain tolerance. Nm-scale voids within PVD columns lower thermal conductivity. Off-Axis (~55 o ) nm-scale globular voids. Crystallographic Texture in EB-DVD Coating Distances reported are substrate-to-region of interest. 40  m 80  m 180  m 20  m 5  m SEM Images of EB-DVD coating. 200  m 59  m (111) (200) (202) (131) (222) (400) (111) (200) (202) (131) (222) (400) (111) (200) (202) (131) (222) (400) Systems which exhibit anisotropic growth patterns with preferential orientations, as in PVD coatings, were not possible to analysis using existing small- angle scattering analysis routines. Recently, a scattering model which fits scattering from a system of idealized anisotropic objects to the measured scattering data has been used to quantify scattering from such features. Fitting the 2-D collimated USAXS I vs. Q data to appropriate anisotropic models has been performed at NIST 2. Void size and orientation distributions from are reported in Table 1. Results represent statistical scattering data from ~0.008mm 3 sample volume. Similar anisotropic models can be applied to HESAXS data. Small Angle X-ray Scattering from Anisotropic Voids. P(  ) and P(  ) are orientation distributions. where Mathematical formulation which describes I vs. Q for idealized anisotropic scatterers having preferential orientation distributions. Characterization by 2-D Collimated USAXS 1, shows finer void sizes after thermal cycling of electron beam physical vapor deposited (EB-PVD) coatings X-ray Operations and Research As-Deposited As-Deposited EB-PVD Coating Void Populations  -Orientation Aspect RatioMean (nm) Volume (%) 1:Intercolumnar85 o ± 709.0±0.9 2:Coarse Intracolumnar 55 o ±202.8 ± 0.3 3:Fine (nm) Intracolumnar 65 o ±24.9 ± 0.5 4:Globular58 o ±204.7± 0.4 Thermally Cycled EB-PVD Coating (10 Cycles comprised of 30 min. heat and 15 min. cool) Void Populations  -Orientation Aspect RatioMean (nm) Volume (%) 1:Intercolumnar85 o ± ± 1.0 2:Coarse Intracolumnar 55 o ± ± 0.7 3:Fine (nm) Intracolumnar 65 o ±42.38 ± 0.3 4:Globular58 o ±206.0± Data ---Model Anisotropic USAXS from orthogonal slices (Y,Z) in as-deposited EBPVD coating shows model fits to data in several directions and azimuthal orientations. Y Z Q= A -1 Q= A -1 X-ray Computed Microtomograph (XMT), reveals the 3-D intercolumnar void microstructure. Efforts are underway to quantify these images via image analysis. High magnification image showing 3-D void interconnectivity.