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1452 |
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Metastable phases in thermally flame and plasma sprayed mullite/ZrO2 coatings |
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Sergi Dosta / Thermal Spray Centre (CPT) - Universitat de Barcelona, SPAIN C. Cano / Instituto de Cerámica y Vidrio, CSIC, Spain E. García*/ Instituto de Cerámica y Vidrio, CSIC, Spain M.I. Osendi/ Instituto de Cerámica y Vidrio, CSIC, Spain P. Miranzo/ Instituto de Cerámica y Vidrio, CSIC, Spain I.G. Cano/ Thermal Spray Centre (CPT), Spain J.M. Guilemany/ Thermal Spray Centre (CPT), Spain |
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Thermally sprayed ceramic coatings are commonly used in technological applications for protecting metal or even ceramic components against temperature, corrosion and erosion. Mullite based materials present interesting properties for high temperature applications, in particular, for environmental barrier coatings (EBCs) on SiC-based components for the next generation of turbines. Among mullite based materials mullite/ZrO2 composites are the most commonly studied as they present improved mechanical properties. The objective of the present work was to study the thermal spraying deposition of mullite/ZrO2 coatings by different techniques, flame, plasma and high velocity oxyfuel spraying processes. A mullite/ZrO2 80/20% v/v composition has been selected because it is very close to the eutectic one and it is located in the ZrO2 primary crystallization field of the corresponding equilibrium phase diagram. For that purpose, mullite/ZrO2 mixtures were prepared and conditioned for thermal spraying starting from mullite and m-ZrO2 commercial powders. Microstructure and phases formed in the coatings have been comparatively analysed. As-sprayed coatings were mainly amorphous and contained metastable phases according to the corresponding equilibrium phase diagram. These coatings partially crystallised when treated at high temperature (>1000 ºC). Hardness of the coatings correlates with the amount of crystalline phases and the porosity. |