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1310 |
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Wednesday, June 04, 2008, Room 08 4:20 PM Ceramics Coatings for wear resistance and high temperature applications |
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Mullite-zirconia ceramics production by plasma spray coating process |
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Nil Toplan / Sakarya University, Engineering Faculty, Dept. of Metallurgical and Materials Eng., Turkey Garip Erdogan* / Sakarya University, TURKIYE Fatih Ustel/ Sakarya University, TURKIYE |
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Zircon (ZrSiO4), is one of the technologically important oxide ceramic materials known for its high refractoriness and chemical stability. It shows excellent thermal shock resistance as a result of its very low thermal expansion coefficient and low heat conductivity coefficient. Mullite has high melting point, chemical stability, low thermal expansion, high creep and thermal shock resistance, and attractive bending strength at high temperatures. The toughening of mullite ceramics by ZrO2 inclusions allows an increase in the strength and toughness at intermediate temperatures, where the properties of mullite ceramics are not as good as those of alumina ceramics. Plasma spraying is a convenient method to produce large area coatings with high growth rates, necessary for many applications ZrSiO4 is among the cheapest spraying materials for refractory applications. In this study, a single-step process was purposed to prepare mullite/zirconia ceramic composites by plasma spraying zircon/alumina mixtures. Mixtures of ZrSiO4 and Al2O3 powders with Al2O3+SiO2 molar ratios of 3:2 were milled for 2 h in zirconia ball milling medium using ball mill. The as-milled powders were dried in furnace and sintered at 1100 ¢XC and 1300¢XC for 2h then sieved under 100?Ým. The powders were sprayed by atmosferic plasma spray gun (40kW) using Al and steel based substrates. Electron microscopy was used to analyze the microstructures of the powders and the coatings. While the phase composition analysis of powders showed the presence of alumina and zircon and alumina, zircon, zirconia and mullite phases were determined after coating. Keywords: Alumina/zircon mixtures, powder processing, plasma spray, mullite-zirconia ceramics |