ASSESSMENT OF MICROSTRUCTURE AND MECHANICAL PROPERTIES OF ZRO2 BASED PLASMA SPRAYED COATINGS
Keywords:
Plasma spraying, Multilayer coatings, Tensile bond strength, Thermal mismatch strainAbstract
The demand for improved performance in high-temperature mechanical systems has led to increasingly harsh operating environments, particularly for the components in advanced gas turbine engines. Future improvements in gas turbine performance will require even higher thermal efficiencies, longer operating lifetimes, and reduced emissions. Higher efficiency requires the gas turbines to operate at higher temperatures. However, such high heat input weakens the structure of the gas turbine. Therefore, ceramic thermal barrier coatings (TBCs) are widely used as insulation materials protecting the underlying metallic structure of a gas The TBCs are often composed of several layers. The typical TBC is composed of double layers including the bond coat and top coat. Among the available coating materials ZrO2 based ceramic coating exhibits low thermal conductivity and higher thermal cycling life. Performance of the coating depends on the microstructure of TBCs and mechanical properties such as tensile adhesion and bending strength. In this work, effect of coating material on microstructure and mechanical properties were investigated. Five different coating systems were deposited by atmospheric plasma spraying. Tensile bond strength of the TBC coating system was evaluated according to the ASTM C-633 standard. The results shows that coatings deposited with multilayer structure exhibits higher bond strength when compared with the coatings deposited without interlayer. Furthermore, it was inferred that multilayered coatings reduces the thermal mismatch strain was the primary reason to increase the tensile bond strength of the developed coating.
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