Exploring thermal spray gray alumina coating pore network architecture by combining stereological protocols and impedance electrochemical spectroscopy |
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Authors: | G Antou G Montavon F Hlawka A Cornet C Coddet |
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Affiliation: | (1) SPCTS UMR, CNRS 6638, Faculty of Sciences, University of Limoges, 123 Avenue Albert Thomas, 87 060 Limoges Cedex, France;(2) LGECO-GLISS, INSA Strasbourg, 24 Boulevard de la Victoire, 67 000 Strasbourg, France;(3) LERMPS, UTBM, Site de Sévenans, 90 010 Belfort Cedex, France |
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Abstract: | Complex multiscale pore network architecture characterized by multimodal pore size distribution and connectivity develops
during the manufacture of ceramic thermal spray coatings from intra- and interlamellar cracks generated when each lamella
spreads and solidifies to globular pores resulting from lamella stacking defects. This network significantly affects the coating
properties and their in-service behaviors. De Hoff stereological analysis permits quantification of the three-dimensional
(3D) distribution of spheroids (i.e., pores) from the determination of their two-dimensional (2D) distribution estimated by
image analysis when analyzing the coating structure from a polished plane. Electrochemical impedance spectroscopy electrochemically
examines a material surface by frequency variable current and potential and analyzes the complex impedance. When a coating
covers the material surface, the electrolyte percolates through the more or less connected pore network to locally passivate
the substrate. The resistive and capacitive characteristics of the equivalent electrical circuit will depend upon the connected
pore network architecture. Both protocols were implemented to quantify thermal spray coating structures. Al2O3-13TiO2 coatings were atmospherically plasma sprayed using several sets of power parameters, are current intensity, plasma gas total
flow rate, and plasma gas composition in order to determine their effects on pore network architecture. Particle characteristics
upon impact, especially their related dimensionless numbers, such as Reynolds, Weber, and Sommerfeld criteria, were also determined.
Analyses permitted identification of (a) the major effects of power parameters upon pore architecture and (b) the related
formation mechanisms.
This article was originally published inBuilding on 100 Years of Success, Proceedings of the 2006 International Thermal Spray Conference (Seattle, WA), May 15–18, 2006, B.R. Marple, M.M. Hyland, Y.-Ch. Lau, R.S. Lima, and J. Voyer, Ed., ASM International, Materials
Park, OH, 2006. |
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Keywords: | connected pore crack electrochemical impedance spectroscopy globular pore image analysis pore network stereology thermal spray coating structure |
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