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Fabrication and Characterization of Amorphous Alumina-Yttria-Stabilized Zirconia Coatings by Air Plasma Spraying

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Details

Original languageEnglish
Pages (from-to)1302-1311
Number of pages10
JournalJournal of Thermal Spray Technology
Volume23
Issue number8
DOIs
Publication statusPublished - 25 Nov 2014
Publication typeA1 Journal article-refereed

Abstract

Almost fully amorphous coatings of near-eutectic alumina-yttria-stabilized zirconia (Al2O3-YSZ) were prepared by air plasma spraying using Al2O3and 8 mol.% YSZ crystalline-mixed powders. The coatings consist of mostly an amorphous phase with a small amount of nanocrystals. Various characterization techniques were used to understand coating formation and the origins of the different phases within the coatings. The formation of the mostly amorphous structure is attributed to the high glass-forming ability of Al2O3-YSZ and the appropriate plasma spraying conditions. A small number of nanocrystals are produced during crystallization of the incoming molten droplets or by recrystallization of the solidified splats by accumulated heat. Scanning electron microscopy shows that the coatings have a dense, layered structure with low porosity, and bright-field transmission electron microscopy images indicate sharp interface rather than grit-blasted wavy surface between splats and substrates in the coatings. The as-sprayed amorphous coatings crystallized at around 920 °C and micro-hardness of the as-sprayed amorphous coatings was 8.12 GPa.

Keywords

  • alumina-yttria-stabilized zirconia, amorphous phases, atmospheric plasma spraying, micro-hardness, nanocrystals, thermal stability