Recent Developments in the Characterization of Extreme-Anisotropic

1. Thermally Cycled EB-PVD Coating (10 Cycles comprised of 30 min. heat and 15 min. cool) As-Deposited EB-PVD Coating Void Populations Void Populations a -Orientation a -Orientation Aspect Ratio Aspect Ratio Mean <O.D.> (nm) Mean <O.D.> (nm) Volume (%) Volume (%) X-ray Operations and Research 1: 1: Intercolumnar Intercolumnar 85o 85o 0.15 0.2 551.02 ±55 733.82 ±70 9.0±0.9 9.59± 1.0 2: 2: Coarse Intracolumnar Coarse Intracolumnar 55o 55o 0.1 0.07 173.83±20 141.56±14 6.98 ± 0.7 2.8 ± 0.3 3: 3: Fine (nm) Intracolumnar Fine (nm) Intracolumnar 65o 65o 0.05 0.05 22.00±2 38.47±4 4.9 ± 0.5 2.38 ± 0.3 4: 4: Globular Globular 58o 58o 0.1 0.7 150±20 140±20 6.0± 0.06 4.7± 0.4 X-ray Computed Microtomograph (XMT), reveals the 3-D intercolumnar void microstructure. Efforts are underway to quantify these images via image analysis. Crystallographic Texture in EB-DVD Coating High magnification image showing 3-D void interconnectivity. (222) (222) (222) (202) (202) (202) 180mm 80mm 40mm (131) (131) (131) (200) (200) (200) (400) (400) (400) (111) (111) (111) 5 mm Off-Axis (~55o ) nm-scale globular voids. 59mm 200mm Figure 1. Schematic illustrates void microstructures in PVD coatings. mm-scale voids between PVD columns impart strain tolerance. Nm-scale voids within PVD columns lower thermal conductivity. 20 mm Summary SEM Images of EB-DVD coating. Q=0.00026 A-1 Q=0.00101 A-1 ---Data ---Model 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. Small Angle X-ray Scattering from Anisotropic Voids. Distances reported are substrate-to-region of interest. Y 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 NIST2. Void size and orientation distributions from are reported in Table 1. Results represent statistical scattering data from ~0.008mm3 sample volume. Similar anisotropic models can be applied to HESAXSdata. Z Anisotropic USAXS from orthogonal slices (Y,Z) in as-deposited EBPVD coating shows model fitsto data in several directions and azimuthal orientations. P(a) and P(w) are orientation distributions. where Mathematical formulation which describes I vs. Q for idealized anisotropic scatterers having preferential orientation distributions. Recent Developments in the Characterization of Extreme-Anisotropic Void Populations in Advanced Thermal Coatings TA Dobbins1, AJ Allen1, J Ilavsky1,2,D Hass3, H Wadley3 , A Kulkarni4 , J Almer5, F DeCarlo5 1. Ceramics Division, Materials Science and Engineering Laboratory, NIST, Gaithersburg, MD 20899 2. Dept. of Chemical Engineering, Purdue University, West Lafayette, IN 47907  3. Intelligent Processing of Materials Laboratory, University of Virginia, Charlottesville, VA 22904 4. NSF Center for Thermal Spray Research, SUNY Stony Brook, Stony Brook, NY 11794-2275 5. Argonne National Laboratory, Advanced Photon Source - XOR Motivation 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. Characterized by HESAXS and WAXD using 5 mm by 50 mm beam size, electron beam directed vapor deposited (EB-DVD) coatingsshow transformation from equiaxed growth (continuous rings) to textured growth (uneven rings). Small angle scattering shows ‘off-axis’ voids more prominent farther from substrate. Characterization by 2-D Collimated USAXS1, shows finer void sizes after thermal cycling ofelectron beam physical vapor deposited (EB-PVD) coatings As-Deposited References • J. Ilavsky, A.J. Allen, G.G. Long, P.R. Jemian, Review of Scientific Instruments73[3] 1660 (2002). • 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 Proceedings24[3/4], 2003. 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-31-109-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