Thermally Grown Oxide Growth Behavior and Its Impedance Properties of Thermal Barrier Coatings with Cold Sprayed and Low Pressure Plasma Sprayed Bond Coatings

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In this study, the influence of bond coating process for a thermal barrier coating (TBC) on thermally grown oxide (TGO) growth was investigated, which used in advanced gas turbine system. The bond coats (BCs) were sprayed by different spray techniques, namely the low pressure plasma spraying (LPPS) and the cold spraying (CS). Yttria Stabilized Zirconia (YSZ) top coat was subsequently fabricated on the BC layer by air plasma spraying (APS). The coatings were oxidized isothermally at 1000°C for different time periods up to 1000h. The TGO growth was measured considering oxidation rate, k, and impedance measurement.The results showed that the TGO growth of the TBC with CS-BC is less than that of the TBC with LPPS. In the case of the TBC with CS-BC, formation of mixed oxides is less than the LPPS one, which has harmful influence on delamination of the top coating. Resultantly, the CS-BC has much higher resistivity than the LPPS. We observed that the bond coating process affected the generation and growth behavior of the TGO, especially high temperature oxidation rate. The present study concluded that the CS-BC system is able to generate better quality TGO.