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Tuesday, May 16, 2006 - 4:40 PM
MDS4.4

Modeling Thermal Conductivity of Thermal Spray Coatings: Comparing Predictions to Experiments

Y. Tan, J. P. Longtin, Stony Brook University, Stony Brook, NY; S. Sampath, S.U.N.Y at Stony Brook, Stony Brook, NY

Thermal conductivity and electrical resistivity play a critical role in the thermal and electrical transport of thermal sprayed coatings.  In this paper, a combined image analysis and finite element method approach is developed to estimate thermal and electrical resistivity from high-resolution scanning electron microscopy images of the coating microstructure.  Images are analyzed with a collection of image processing algorithms to reveal the microscopic detailed coating morphology.  The processed digital image is used to generate a two-dimensional finite element meshing in which pores, cracks and the bulk coating material are identified.  The effective thermal conductivity or electrical resistivity is then simulated using a commercial finite element code.  Results are presented for three coating material systems processed through various thermal spray methods: yttria stabilized zirconia (YSZ), Molybdenum and NiAl, and results are found to be in good agreement with experimental values from the laser flash method.  Coatings are also annealed and the analysis procedure repeated to determine if the technique can accurately assess changes in coating morphology. 
Keywords: Thermal Sprayed Coatings, Image Analysis, Finite Element Method, Thermal Conductivity, Electrical Resistivity

Summary: This work presents a FEM-based numerical model of the thermal conductivity. The mesh used for the model is taken from high-resolution SEM images of coating cross-sections. Agreement is generally good between measured and predicted values for YSZ, Mo, and NiAl.