| Abstract: |
Thermal barrier coating (TBC) has emerged as arguably the most critical materials issue for the next generation of gas turbine technology. Its applications continue to increase as the need for a greater engine efficiency that can be achieved through higher operating temperatures increases. Commercial TBC systems typically consist of a metallic bondcoat applied to a Ni-based superalloy substrate and a ceramic topcoat. Yttria-stabilized zirconia (YSZ) is commonly used as the ceramic coating (topcoat) because of its low thermal conductivity and relatively high thermal expansion coefficient. The metallic bondcoat must be resistant to both thermomechanical fatigue and oxidation since YSZ coating is essentially a porous layer that is transparent to oxygen penetration. (materials letters 57 (2002) 628-634)
The objective of the present work is to produce YSZ? 20, 50 and 80 wt % Al2O3 powders and coatings which are used for jet engines, gas turbines and diesel engines, many components are coated with TBCs to provide high thermal resistance and reduce the metal surface temperatures, thus increasing component durability. Starting powders were YSZ, and Al2O3 powders were mixed in the compositions of YSZ ? 20, 50 and 80 wt % Al2O3. The mixtures were ball milled for 2h by using ZrO2 balls to provide homogenous mixtures. The coatings were formed using a METCO 3MB plasma spray gun on stainless steel substrates. Electron microscopy was used to analyze the microstructures of powders and coated samples. The microhardness and surface roughness were investigated depending of the alumina contents.
Keywords: Thermal barrier coatings, ZrO2/Al2O3 coating powders, microhardness, surface roughness
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