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| Abstract No.: |
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Scheduled at:
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Wednesday, June 07, 2017, Hall Y 11:50 AM
Plasma Spraying I
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| Title: |
Porosity characterization and its effect on thermal properties of APS sprayed alumina coatings
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| Authors: |
Omar Khalil* / University of Dortmund, Germany
Wolfgang Tillmann / Technische Universität Dortmund, Germany
Mohamed Abdulgader/ Technische Universität Dortmund, Germany
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| Abstract: |
Abstract
In the present work, three different APS alumina coatings were fabricated using three fused & crushed alumina powders of different particle size; fine, medium and coarse. The influence of particle size on thermal properties and micro-structural features of the produced coating were investigated in details using image analysis technique. The analyzed micro-structural features include total porosity, globular porosity, inter-lamellar pores and crack network. All spray parameters were fixed throughout the spraying process except the particle size. The results revealed that the fine starting powder has produced the densest coating with the lowest total porosity and that total porosity increases with increasing particle size. This was expected as powders of smaller particle size, will gain higher in-flight temperature and velocity than that of bigger particle size as long as the same spray parameters have been applied. However, detailed image analysis investigation on the three produced coatings showed that the fraction of inter-lamellar pores and cracks versus globular porosity is substantially higher in coatings produced using fine starting powder than that produced using medium and coarse powders. A relation has been established in this work between thermal diffusivity and the porosity fraction that includes inter-lamellar pores and cracks.
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