Mullite-zircon thermal barrier coating production by plasma spraying process

摘要

Zircon, (ZrSiO{sub}4), 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 a low heat conductivity coefficient. Plasma spraying is a convenient method to produce large area coatings with high growth rates, necessary for many applications. ZrSiO{sub}4 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 ZrSiO{sub}4 and Al{sub}2O{sub}3 powders with Al{sub}2O{sub}3 to SiO{sub}2 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 the furnace and sintered at 1300℃ and 1350℃ for 2h then crushed under 100μm. The powders were sprayed by atmospheric plasma spray gun ((Metco 3MB) using C/C+SiC ceramic matrix composite substrates. Scanning electron microscopy (SEM) was used to analyze the microstructures of the powders and plasma coatings. While the phase composition analysis of powder showed the presence of alumina and zircon and alumina, zircon, zirconia and phases were determined after the plasma coating.