S044025 Evaluation of Thermally Grown Oxides Formation and Growth Behavior of Thermal Barrier Coatings with Cold Sprayed Bond Coatings

Abstract

Thermal barrier coatings (TBCs) for blades of gas turbines are an indispensable technology for improvement of the turbine efficiency. During service, a thermally grown oxide (TGO), which has harmful influence on delamination of the TBC, grows at the interface between the TBC and a bond coat (BC). In this study, the influence of bond coating process for the TBC on the TGO growth was investigated The 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 1273K for different time periods up to 1000h and their TGO growth were compared and fully discussed by measuring their TGO thickness, and impedance measurement of their TGOs. As a result, it can be found that the TGO growth of the TBC with CS-BC was less than that of the TBC with LPPS one. And also, in the case of the TBC with CS-BC, formation of mixed oxides, which are porous and crack initiation site, was less than LPPS one. And it was found that CS-BC impedance was much higher than LPPS-BC one from the results of impedance measurements. It concluded that the TBC with CS-BC can be generated and grew much higher quality TGO than that of the LPPS-BC.