Isothermal Oxidation Behavior of Gd 2 Zr 2 O 7 /YSZ Multilayered Thermal Barrier Coatings

Efficiency of a gas turbine can be increased by increasing the operating temperature. Yttria‐stabilized zirconia ( YSZ ) is the standard thermal barrier coating ( TBC ) material used in gas turbine applications. However, above 1200°C, YSZ undergoes significant sintering and CMAS (calcium magnesium alumino silicate) infiltration. New ceramic materials of rare earth zirconate composition such as gadolinium zirconate ( GZ ) are promising candidates for thermal barrier coating applications ( TBC ) above 1200°C. Suspension plasma spray of single‐layer YSZ , double‐layer GZ / YSZ , and a triple‐layer TBC comprising denser GZ on top of GZ / YSZ TBC was attempted. The overall coating thickness in all three TBC s was kept the same. Isothermal oxidation performance of the three TBC s along with bare substrate and bond‐coated substrate was investigated for time intervals of 10 h, 50 h, and 100 h at 1150°C in air environment. Weight gain/loss analysis was carried out by sensitive weighing balance. Microstructural analysis was carried out using scanning electron microscopy ( SEM ). As‐sprayed single‐layer YSZ and double‐layer GZ / YSZ showed columnar microstructure, whereas the denser layer in the triple‐layer TBC was not columnar. Phase analysis of the top surface of as‐sprayed TBC s was carried out using XRD . Porosity measurements were made by water intrusion method. In the weight gain analysis and SEM analysis, multilayered TBC s showed lower weight gain and lower TGO thickness compared to single‐layer YSZ .