Influence of Bondcoat Topography on the Properties of Suspension Sprayed YSZ Thermal Barrier Coatings

2021 ◽  
Author(s):  
Filofteia-Laura Toma ◽  
Julia Sagel ◽  
Christoph Leyens ◽  
Karel Slámečka ◽  
Serhii Tkachenko ◽  
...  
Keyword(s):  
Thermal Barrier Coatings ◽  
Physical Vapor Deposition ◽  
Thermal Spraying ◽  
Ceramic Coatings ◽  
Cycling Performance ◽  
Thermal Barrier ◽  
Oxide Ceramic ◽  
Air Plasma ◽  
Barrier Coatings ◽  
Direct Laser

Abstract Intensive R&D work of more than one decade has demonstrated many unique coating properties; particularly for oxide ceramic coatings fabricated by suspension thermal spraying technology. Suspension spraying allows producing yttria-stabilized zirconia (YSZ) thermal barrier coatings (TBC) with columnar microstructure; similar to those produced by electron-beam physical vapor deposition (EB-PVD); and vertically cracked morphologies; with a generally low thermal conductivity. Therefore; suspension sprayed YSZ TBCs are seen as an alternative to EB-PVD coatings and those produced by conventional air plasma spray (APS) processes. Nonetheless; the microstructure of the YSZ topcoat is strongly influenced by the properties of the metallic bondcoat. In this work; direct laser interference patterning (DLIP) was applied to texture the surface topography of Ni-alloy based plasma sprayed bondcoat. Suspension plasma spraying (SPS) was applied to produce YSZ coatings on top of as-sprayed and laser-patterned bondcoat. The samples were characterized in terms of microstructure; phase composition and thermal cycling performance. The influence of the bondcoat topography on the properties of suspension sprayed YSZ coatings is presented and discussed.

Characterization of thermal barrier coatings formed by electon-beam physical vapor deposition (EB-PVD)

1989 ◽  
Vol 47 ◽  
pp. 426-427
Author(s):  
Ozer Unal
Keyword(s):  
Thermal Barrier Coatings ◽  
Physical Vapor Deposition ◽  
Ceramic Coating ◽  
High Vacuum ◽  
Ceramic Coatings ◽  
High Energy ◽  
Thermal Barrier ◽  
Protective Oxide ◽  
Barrier Coatings ◽  
Energy Beam

Interest in ceramics as thermal barrier coatings for hot components of turbine engines has increased rapidly over the last decade. The primary reason for this is the significant reduction in heat load and increased chemical inertness against corrosive species with the ceramic coating materials. Among other candidates, partially-stabilized zirconia is the focus of attention mainly because ot its low thermal conductivity and high thermal expansion coefficient.The coatings were made by Garrett Turbine Engine Company. Ni-base super-alloy was used as the substrate and later a bond-coating with high Al activity was formed over it. The ceramic coatings, with a thickness of about 50 μm, were formed by EB-PVD in a high-vacuum chamber by heating the target material (ZrO2-20 w/0 Y2O3) above its evaporation temperaturef >3500 °C) with a high-energy beam and condensing the resulting vapor onto a rotating heated substrate. A heat treatment in an oxidizing environment was performed later on to form a protective oxide layer to improve the adhesion between the ceramic coating and substrate. Bulk samples were studied by utilizing a Scintag diffractometer and a JEOL JXA-840 SEM; examinations of cross-sectional thin-films of the interface region were performed in a Philips CM 30 TEM operating at 300 kV and for chemical analysis a KEVEX X-ray spectrometer (EDS) was used.

scholarly journals The Numerical Modeling of Thermal Stress Distribution in Thermal Barrier Coatings

2017 ◽  
Vol 62 (3) ◽  
pp. 1433-1437
Author(s):  
A. Jasik
Keyword(s):  
Thermal Stress ◽  
Stress Distribution ◽  
Thermal Barrier Coatings ◽  
Bond Coat ◽  
Thermal Spraying ◽  
Ceramic Coatings ◽  
Thermal Barrier ◽  
Insulation Layer ◽  
Barrier Coatings ◽  
Thermal Stress Distribution

Abstract The paper presents the results of numerical calculations of temperature and thermal stress distribution in thermal barrier coatings deposited by thermal spraying process on the nickel based superalloy. An assumption was made to apply conventional zirconium oxide modified with yttrium oxide (8YSZ) and apply pyrochlore type material with formula La2Zr2O7. The bond coat was made of NiCoCrAlY. Analysis of the distribution of temperature and stresses in ceramic coatings of different thicknesses was performed in the function of bond-coat thickness and the type of ceramic insulation layer. It was revealed that the thickness of NiCrAlY bond-coat has not significant influence on the stress distribution, but there is relatively strong effect on temperature level. The most important factor influenced on stress distribution in TBC system is related with type and properties of ceramic insulation layer.

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.

Health Monitoring and Life Prediction of Thermal Barrier Coatings Using a Laser-Based Method

2005 ◽  
Author(s):  
Robert J. Visher ◽  
Luis Gast ◽  
William A. Ellingson ◽  
Albert Feuerstein
Keyword(s):  
Thermal Barrier Coatings ◽  
Bond Coat ◽  
Gas Turbines ◽  
Physical Vapor Deposition ◽  
Laser System ◽  
Experimental Results ◽  
Thermal Barrier ◽  
Air Plasma ◽  
Thermal Cycles ◽  
Barrier Coatings

Thermal barrier coatings (TBCs) are a critical component in low-emission gas turbines. A reliable method is required to monitor the condition of the TBC and predict coating failure. The condition of the interface between the metallic bond coat and TBC has been shown to be a potential indicator of spallation. The TBC is optically translucent; therefore, the bond coat/TBC interface can be probed using laser light with a wavelength of 0.632 microns or higher. A laser system in an optical backscatter configuration has been used to investigate several yttria-stabilized zirconia (YSZ) TBCs applied with either electron-beam physical vapor deposition (EB-PVD) or air plasma spraying (APS). The TBCs were thermally cycled for one hour increments until failure and investigated by the laser backscatter method after set numbers of thermal cycles. Correlations have been established between laser backscatter data and the number of thermal cycles, suggesting that the laser backscatter method can be used to predict failure. A theoretical model has been used to compare interface topography scatter to experimental results. This paper will discuss the laser backscatter technique and the experimental results and will compare the experimental data and theoretical scatter.

Numerical Simulation for Surface Modification of Thermal Barrier Coatings by High-Current Pulse Electron Beam

2010 ◽  
Vol 654-656 ◽  
pp. 1807-1810
Author(s):  
Ying Qin ◽  
Wei Qu ◽  
Xian Xiu Mei ◽  
Sheng Zhi Hao ◽  
Ji Jun Zhao ◽  
...  
Keyword(s):  
Electron Beam ◽  
Thermal Barrier Coatings ◽  
Physical Vapor Deposition ◽  
Turbine Blades ◽  
Ceramic Coatings ◽  
Pulse Electron Beam ◽  
Thermal Barrier ◽  
High Current ◽  
Barrier Coatings ◽  
Pulsed Electron Beam

High current pulsed electron beam is an effective technique for surface sealing of ceramic thermal barrier coatings prepared by electron beam physical vapor deposition. Due to the rapid remelting and solidification, the outer layers of ceramic coatings become smooth and dense, and the protective performance for turbine blades is effectively improved. Because of the complex multi-layered structures in the coatings, a high-current pulsed electron beam treatment requires specific parameter inputs which are related to the temperature field induced by electron energy deposition in the coatings. In this paper, a two-dimensional temperature simulation was performed to demonstrate the melting depth and temperature evolution in ceramic coatings treated by high-current pulsed electron beam. Different energy densities and pulses were studied and discussed for obtaining optimized parameters.

Development and Performance Evaluation of Thick Air Plasma Sprayed Thermal Barrier Coatings

2000 ◽  
Author(s):  
Z.Z. Mutasim ◽  
Y.L. Nava
Keyword(s):  
Thermal Barrier Coating ◽  
Thermal Barrier Coatings ◽  
Ceramic Coatings ◽  
Thermal Barrier ◽  
Air Plasma ◽  
Barrier Coatings ◽  
Barrier Coating ◽  
And Performance ◽  
Plasma Sprayed ◽  
Industrial Gas Turbine

Abstract Air plasma sprayed thermal barrier coatings have been widely used to reduce metal wall temperatures of industrial gas turbine combustor liners. Thermal barrier coatings provide thermal gradients, with the goal of reducing the liner wall temperature to acceptable levels as a result of their low thermal conductivity. A typical thermal barrier coating consists of a 0.1-0.2 mm MCrAlY bond coating and a 0.25-0.35 mm thick 8 wt.% yttria stabilized zirconia ceramic top coating. A method to increase thermal barrier coating effectiveness is the application of thicker ceramic coatings. Development and performance testing of 0.5-0.8 mm thick ceramic coatings are discussed in this paper. Cyclic oxidation tests that simulate industrial gas turbine environments were conducted. Thermal barrier coating degradation-mechanisms were determined from microstructural evaluation of thermally exposed samples.

scholarly journals An image-based model for the sintering of air plasma sprayed thermal barrier coatings

2021 ◽  
Vol 206 ◽  
pp. 116649
Author(s):  
Xun Zhang ◽  
Alan C.F. Cocks ◽  
Yoshifumi Okajima ◽  
Kazuma Takeno ◽  
Taiji Torigoe
Keyword(s):  
Thermal Barrier Coatings ◽  
Thermal Barrier ◽  
Air Plasma ◽  
Barrier Coatings ◽  
Plasma Sprayed
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