Effect of Air Plasma Spray Parameters on the Properties of YSZ and C-YSZ Thermal Barrier Coatings

Thermal Barrier Coatings (TBC) find a wide application area as a protection shield against high temperature for the structural components in stationary and aerospace gas turbines. The Thermal Barrier Coating (TBC) concept is based on placing a thermally insulating layer between a cooled metallic component and the hot working gas with the aim of reducing the heat transfer to the component. Ceramic layer, known as thermal insulating layer, is applied in order to improve adhesive strength, oxidation and corrosion resistance and also to reduce the thermal expansion differences and on the other hand a metallic layer as a bond coat, MCrAlY (M = Co, Ni ), is coated between ceramic layer and substrate. YSZ and C-YSZ are known as the most commonly used coating materials due to their low thermal conductivity and having close characteristics like metals in terms of thermal expansion coefficient, good corrosion resistance. Plasma spray process parameters, such as spray distance and gas mixture ratio have vital impact on thermal barrier coating properties. In this study; metallic bond coat and ceramic thermal insulating layer are conducted by HVOF (High Velocity Oxy Fuel) and APS (Atmospheric Plasma Spray) processes, respectively. Effects of plasma spray distance and Ar/H gas mixture ratio on YSZ and Z-YSZ thermal barrier coating properties are investigated with the experiments and characterization studies. Within the scope of characterization studies; SEM analysis, adhesion strength test compliance with ASTM C633, porosity analysis with ASTM 2109 standard, and also micro-hardness tests are performed.