Mechanical and High Temperature Oxidation Properties of Cold Sprayed CoNiCrAlY Coatings for Thermal Barrier Coating

Abstract

Cold spraying, which is one of the spraying systems for particle deposition, has been studied as a new system of bond coatings of Thermal Barrier Coatings (TBCs) for components used in hot section of advanced gas turbine systems. In this paper, mechanical and oxidation properties including residual stress of Atmospheric Plasma Sprayed (APS) yttria-stabilized zirconia (YSZ) top coating with two different bond coating spraying systems, Low Pressure Plasma Spraying (LPPS) and the cold spraying, were evaluated and compared in thermal cycle tests. From the results, the porosity of the cold sprayed CoNiCrAlY bond coating is less than 4.2%. The relatively less oxidation layer is observed due to its higher density and more stable oxide growth. In-situ measurement of residual stress in the vicinity of the interface between bond coating and top coating shows that variations of residual stress between the thermal and the cold sprayed coatings are different. In particular, both coatings' residual stresses after thermal cycle test were compression due to oxide formation. The thermal sprayed coating had more oxidation layer than the cold sprayed coating. Therefore, compressive residual stress of the thermal sprayed coating was 40 MPa higher than the cold sprayed coating.