Predicting the Thermal Conductivity of AlSi/Polyester Abradable Coatings: Effects of the Numerical Method
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odolphe Bolot, Jean-Louis Seichepine, Jiang Hao Qiao, and Christian Coddet (Submitted April 29, 2010; Accepted August 25, 2010) The final target of this study is to achieve a better understanding of the behavior of thermally sprayed abradable seals such as AlSi/polyester composites. These coatings are used as seals between the static and the rotating parts in aero-engines. The machinability of the composite coatings during the friction of the blades depends on their mechanical and thermal effective properties. In order to predict these properties from micrographs, numerical studies were performed with different software packages such as OOF developed by NIST and TS2C developed at the UTBM. In 2008, differences were reported concerning predictions of effective thermal conductivities obtained with the two codes. In this article, a particular attention was paid to the mathematical formulation of the problem. In particular, results obtained with a finite difference method using a cell-centered approach or a nodal formulation allow explaining the discrepancies previously noticed. A comparison of the predictions of the computed effective thermal conductivities is thus proposed. This study is part of the NEWAC project, funded by the European Commission within the 6th RTD Framework programm (FP6).
Keywords
coatings for engine components, coatings for gas turbine components, composite materials, friction and wear, properties of coatings
1. Introduction Thermal spray technologies allow elaborating coatings on surfaces for protection against corrosion, wear, or high temperature environments. Thermal spray processes consist in spraying molten drops of the protective material on the substrate surface. The produced coatings consist of a network of intermingled splats formed by the flattening and solidification of the molten droplets. They present a complex architecture comprising thin inter-lamellar cracks, globular pores, and intra-lamellar cracks (for ceramics) generated by thermal stresses. Moreover, depending on the process and nature of the sprayed material, they may also contain partially molten particles, This article is an invited paper selected from presentations at the 2010 International Thermal Spray Conference and has been expanded from the original presentation. It is simultaneously published in Thermal Spray: Global Solutions for Future Applications, Proceedings of the 2010 International Thermal Spray Conference, Singapore, May 3-5, 2010, Basil R. Marple, Arvind Agarwal, Margaret M. Hyland, Yuk-Chiu Lau, Chang-Jiu Li, Rogerio S. Lima, and Ghislain Montavon, Ed., ASM International, Materials Park, OH, 2011. Rodolphe Bolot, Jean-Louis Seichepine, Jiang Hao Qiao, and Christian Coddet, LERMPS, University of Technology of BelfortMontbe´liard, Belfort, Montbe´liard, France. Contact e-mail: [email protected].
Journal of Thermal Spray Technology
as well as oxides (for metals and alloys). From that complex architecture, thermal spray coatings exhibit effective properties strongly different from those of the bulk mat
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