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Journal of Nanomaterials
Volume 2015 (2015), Article ID 874190, 9 pages
Research Article

Indentations on Air Plasma Sprayed Thermal Barrier Coatings Prepared by Different Starting Granules

1School of Mechanical Systems Engineering, Kookmin University, Seoul 136-702, Republic of Korea
2School of Nano and Advanced Materials Engineering, Changwon National University, Changwon 641-773, Republic of Korea

Received 15 April 2015; Revised 19 August 2015; Accepted 26 August 2015

Academic Editor: Albano Cavaleiro

Copyright © 2015 Yong Suk Heo et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


The effect of starting granules on the indentation properties of air plasma sprayed thermal barrier coatings (TBCs) is investigated in this paper. Various kinds of spray-dried granules are prepared from different processing conditions, especially varying solvent and dispersant, showing a deformed hollow-typed and a filled spherical-typed granule. The similar coating thicknesses are prepared by adjusting process parameters during air plasma spray. All XRD peaks in phase analysis are tetragonal and cubic phases without any monoclinic phase after the starting granules were heat-treated. A relatively porous microstructure of the coating layer could be obtained from the monodisperse granules, while a relatively dense microstructure resulted from the hollow-typed granules. The morphology and distribution of the granules crucially affect the microstructure of thermal barrier coatings and thus have influences on indentation properties such as indentation stress-strain curves, contact damage, and hardness. The implication concerning microstructure design of TBCs for gas turbine applications is considered.