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| Abstract No.: |
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Scheduled at:
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Wednesday, June 04, 2008, Room 04 4:20 PM
Nanomaterials 2
Most coating materials gain superior coating performance when applied as nanostructured coating, new designed materials and optimized processes show promising results for this
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| Title: |
Plasma spray processing of nanostructured partially stabilized zirconia for a strain accommodating inter layer ? splat and coating characteristics
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| Authors: |
Dwijendra Guru / High Temperature and Plasma Lab
Dept. of Mechanical Engineering
Univ. of Minnesota, USA
Joachim Heberlein* / Dept. of Mechnical Engineering, University of Minnesota, USA
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| Abstract: |
Build up of strain within thermal barrier coatings has been identified as one of the main reasons for coating failure. The large volume fraction of grain boundaries in nanostructured materials has been predicted to partially relieve the strain in a coating structure. In plasma spray deposition, coatings are formed by the deposition of feedstock particles undergoing melting in the plasma plume and splattering onto substrates one on top of the other. The morphological characteristics of the splat samples determine the coating characteristics. In this study, the difference in morphological characteristics of regular PSZ (rPSZ) particles and nano-agglomerate PSZ (nPSZ) particles have been investigated to improve our understanding of the stresses and strains within a coating.
Coatings and splat samples were prepared using both nPSZ and rPSZ feedstock. The Triple Torch Plasma Reactor, a reduced pressure plasma spray system was used to prepare the coatings. A pair of tungsten and molybdenum apertures were used to isolate spray particles from the plume for the splat sample depositions. Cross sections of both the splat samples and the coatings were prepared. Image analysis techniques were used on scanning electron microscopy (SEM) images to characterize both the surface and the cross sectional features of the splat samples. Coating porosities were also estimated using image analysis techniques. A greater spacial inhomogeneity is observed within the splat samples prepared with increased plasma Hydrogen concentration, for both the nPSZ and the rPSZ feedstock. In the macro porosity measurements, the nPSZ coatings were found to be less affected by changes in the deposition conditions than the rPSZ coatings. A discussion of the influence of the deposition conditions on the morphology of the splat samples and coatings for both regular and nanostructured feedstock is presented.
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