Strain Tolerance and Microstructure of Thermal Barrier Coatings Produced by Electron Beam Physical Vapor Deposition Process

2006 ◽  
pp. 267-276
Author(s):  
Kunihiko Wada ◽  
Yutaka Ishiwata ◽  
Norio Yamaguchi ◽  
Hideaki Matsubara
Keyword(s):  
Electron Beam ◽  
Thermal Barrier Coatings ◽  
Vapor Deposition ◽  
Physical Vapor Deposition ◽  
Deposition Process ◽  
Thermal Barrier ◽  
Barrier Coatings ◽  
Strain Tolerance ◽  
Physical Vapor Deposition Process ◽  
Vapor Deposition Process

Strain Tolerance and Microstructure of Thermal Barrier Coatings Produced by Electron Beam Physical Vapor Deposition Process

2006 ◽  
Vol 522-523 ◽  
pp. 267-276 ◽  
Author(s):  
Kunihiko Wada ◽  
Yutaka Ishiwata ◽  
Norio Yamaguchi ◽  
Hideaki Matsubara
Keyword(s):  
Electron Beam ◽  
High Temperature ◽  
Thermal Barrier Coatings ◽  
Vapor Deposition ◽  
Physical Vapor Deposition ◽  
Aging Treatment ◽  
Nanoindentation Test ◽  
Thermal Barrier ◽  
Barrier Coatings ◽  
Strain Tolerance

Several kinds of thermal barrier coatings (TBCs) deposited by electron beam physical vapor deposition (EB-PVD) were produced as a function of electron beam power in order to evaluate their strain tolerance. The deposition temperatures were changed from 1210 K to 1303 K depending on EB power. In order to evaluate strain tolerances of the EB-PVD/TBCs, a uniaxial compressive spallation test was newly proposed in this study. In addition, the microstructures of the layers were observed with SEM and Young’s moduli were measured by a nanoindentation test. The strain tolerance in as-deposited samples decreased with an increase in deposition temperature. In the sample deposited at 1210 and 1268 K, high-temperature aging treatment at 1273 K for 10 h remarkably promoted the reduction of the strain tolerance. The growth of thermally grown oxide (TGO) layer generated at the interface between topcoat and bondcoat layers was the principal reason for this strain tolerance reduction. We observed TGO-layer growth even in the as-deposited sample. Although the thickness of the initial TGO layer in the sample deposited at high temperature was thicker, the growth rate during aging treatment was smaller than those of the other specimens. This result suggests that we can improve the oxidation resistance of TBC systems by controlling the processing parameters in the EB-PVD process.

A Comparison Study of Heat Transfer Through Electron Beam Physical Vapor Deposition (EBPVD) and Air Plasma Sprayed (APS) Coated Gas Turbine Blades

2010 ◽  
Author(s):  
Stephen Akwaboa ◽  
Patrick F. Mensah
Keyword(s):  
Heat Transfer ◽  
Electron Beam ◽  
Turbine Blade ◽  
Thermal Barrier Coatings ◽  
Vapor Deposition ◽  
Physical Vapor Deposition ◽  
Thermal Barrier ◽  
Air Plasma ◽  
Barrier Coatings ◽  
Plasma Sprayed

Thermal barrier coatings (TBCs) are applied to blades, vanes, combustion chamber walls, and exhaust nozzles in gas turbines not only to limit the heat transfer through the coatings but also to protect the metallic parts from the harsh oxidizing and corrosive thermal environment. There is a growing interest in operating these hot gas path (HGP) components at optimal conditions which has resulted in a continuous increase of the turbine inlet temperatures (TITs). This has resulted in the increase of heat load on the turbine components especially in the high pressure side of the turbine necessitating the need to protect the HGP components from the heat of the exhaust gases using novel TBC such as electron beam physical vapor deposition thermal barrier coatings (EBPVD TBCs) and Air Plasma Sprayed thermal barrier coatings (APS TBCs). This study focuses on the estimation of temperature distribution in the turbine metal substrate (IN738) and coating materials (EBPVD TBC and APS TBC) subjected to isothermal conditions (1573 K) around the turbine blade. The heat conduction in the turbine blade and TBC systems necessary for the evaluation of substrate thermal loads are assessed. The steady state 2D heat diffusion in the turbine blade is modeled using ANSYS FLUENT computational fluid dynamics (CFD) commercial package. Heat transfer by radiation is fully accounted for by solving the radiative transport equation (RTE) using the discrete ordinate method. The results show that APS TBCs are better heat flux suppressors than EBPVD TBCs due to differences in the morphology of the porosity present within the TBC layer. Increased temperature drops across the TBC leads to temperature reductions at the TGO/bond coat interface which slows the rate of the thermally induced failure mechanisms such as CTE mismatch strain in the TGO layer, growth rate of TGO, and impurity diffusion within the bond coat.

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