Measurement of X-ray Elastic Constants in Plasma Sprayed TBCs
	Users and Staff Julia L. Bjerke, Caterpillar, Inc. Thomas R. Watkins and Camden R. Hubbard, ORNL Background Caterpillar is using coatings in high performance diesel engines and needed x-ray elastic constants (XECs) for thermal barrier coating (TBC) applications. Use of mechanically determined ãbulkä elastic constants is not usually appropriate as they do not account for: elastic anisotropy crystallographic texture XECs will be applied to x-ray residual stress and fatigue studies of TBCs. Summary Plasma-sprayed, yttria stabilized ZrO2 tube mounted in a compression load frame attached to the goniometer (see left). Approach: TBC tube compressed. Load determined by load cell. Surface strain measured with x-ray diffraction at various loads. Behavior linear elastic. Equations solved for XECs. X-Ray elastic constants calculated. 8wt% Y2O3-ZrO2 E331=160 GPa Poisson's Ratio =+0.26 Cubic, tet., & mono. phases present Density =5.390 g/cm3, ~92% dense 2.5wt% Y2O3-25 wt% CeO2-ZrO2 E331=200 GPa Poisson's Ratio =+0.42 Tet. phase & trace impurity present Density =5.355 g/cm3, ~88% dense Reasonable agreement was found with polycrystalline averages based on dense single crystal elastic constants Presentation T. R. Watkins, C. R. Hubbard, and J. L. Bjerke, "Measurement of Elastic Constants in Plasma-Sprayed Zirconia Coatings Using X-Ray Diffraction," presented at the 96th Annual Meeting of the American Ceramic Society, Indianapolis, IN, April 26, 1994.
	Instruments | Applications | Recent Projects | Publications | Staff  User Facility Access and Proposal Form Diffraction UC | Residual Stress UC | Thermophysical Properties UC Diffraction & Thermophysical Prop. Group | High Temperature Materials Laboratory Metals & Ceramics Division | Oak Ridge National Laboratory Acknowledgments URL: http://www.html.ornl.gov/rsuc/tbc.html