Mechanical Behaviour of Air-plasma Sprayed Functionally Graded YSZ-Mullite Environmental Barrier Coatings : A Study via Instrumented Indentation

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Proceedings titleInternational Thermal Spray Conference & Exposition 2010, Thermal Spray: Global Solutions for Future Application (DVS-ASM)
ConferenceInternational Thermal Spray Conference (ITSC) 2010 : Singapore, May 2, 2010
Pages730735; # of pages: 6
AbstractMullite (Al6Si2O13) is the basis of efficient environmental barrier coatings (EBCs) for protecting Si-based ceramic matrix composites (CMCs) selected to replace specific hot-section metallic components in advanced gas turbines. Furthermore, YSZ-mullite multilayer architectures with compositional grading between the bond coat and YSZ top coat were envisioned as solutions to ease their coefficient of thermal expansion (CTE) mismatch induced stress. Consequently, a proper understanding of the mechanical properties such as the elastic modulus, hardness or plastic/elastic recovery work serve for an efficient design of such refractory oxide multilayers. In this work, three different mullite powder morphologies (fused and crushed, spray-dried and freeze-granulated) were employed. Using depth-sensing indentation with loads in the range 100 – 500 mN, the role of the microstructure and morphology of the powder feedstock on the mechanical behaviour of air plasma sprayed mullite bond coats deposited on SiC Hexoloy substrates was investigated. Fully crystalline as-sprayed mullite coatings were engineered under controlled deposition conditions. Mechanical properties were measured for the as-sprayed coatings as well as for coatings heat-treated at 1300oC, in water vapour environment, for periods up to 500 h. Both E and H values of the coatings are found to be highly dependent on the morphology of the starting powders.
Publication date
PublisherASM -- The Materials Information Society
AffiliationNational Research Council Canada (NRC-CNRC); NRC Industrial Materials Institute
Peer reviewedNo
NRC number52405
NPARC number15657367
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Record identifierac5b24b2-76b0-425b-b0d9-c301c9bb1925
Record created2010-06-29
Record modified2016-05-09
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