Effect of Spray Parameters on the Microstructure and Porosity Content of Gadolinium Zirconate TBCs Deposited by Suspension Plasma Spray

Abstract

Abstract Gadolinium zirconate (GZ) is considered as a promising top coat candidate for high temperature (>1200 °C) thermal barrier coating (TBC) applications. Suspension plasma spray (SPS) technique has shown the capability to generate a wide range of microstructures which includes the more desirable columnar microstructure. In this study, GZ single layer TBCs were deposited by axial SPS process. The variable parameters include the standoff distance, solid load content of the suspension and input power. The cross section and top surface of the as sprayed TBCs were analyzed by SEM. The phase content in the as sprayed TBCs was analyzed by XRD. The porosity content of the as sprayed TBCs was measured using image analysis. In the SEM analysis, it was observed that a lower solid load content in the suspension favored the formation of a columnar microstructure. Additionally, at lower solid load content, increase in standoff distance resulted in columnar microstructure with high porosity content in the TBC. However, with higher solid content suspension and alteration of input power, only a dense vertical cracked microstructure can be obtained.