scholarly journals Heat Transfer Through Plasma-Sprayed Thermal Barrier Coatings in Gas Turbines: A Review of Recent Work

2009 ◽  
Vol 18 (5-6) ◽  
pp. 809-821 ◽  
Author(s):  
I. O. Golosnoy ◽  
A. Cipitria ◽  
T. W. Clyne
Keyword(s):  
Heat Transfer ◽  
Recent Work ◽  
Thermal Barrier Coatings ◽  
Gas Turbines ◽  
Thermal Barrier ◽  
Barrier Coatings ◽  
Plasma Sprayed

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.

scholarly journals The Effect of Coating Composition and Geometry on Thermal Barrier Coatings Lifetime

2018 ◽  
Vol 141 (3) ◽  
Author(s):  
Bruce A. Pint ◽  
Michael J. Lance ◽  
J. Allen Haynes
Keyword(s):  
Thermal Barrier Coatings ◽  
Gas Turbines ◽  
Average Lifetime ◽  
Thermal Barrier ◽  
Air Plasma ◽  
Barrier Coatings ◽  
Bond Coatings ◽  
Bond Coating ◽  
Negative Effect ◽  
Plasma Sprayed

Several factors are being investigated that affect the performance of thermal barrier coatings (TBC) for use in land-based gas turbines where coatings are mainly thermally sprayed. This study examined high velocity oxygen fuel (HVOF), air plasma-sprayed (APS), and vacuum plasma-sprayed (VPS) MCrAlYHfSi bond coatings with APS YSZ top coatings at 900–1100 °C. For superalloy 247 substrates and VPS coatings tested in 1 h cycles at 1100 °C, removing 0.6 wt %Si had no effect on average lifetime in 1 h cycles at 1100 °C, but adding 0.3%Ti had a negative effect. Rod specimens were coated with APS, HVOF, and HVOF with an outer APS layer bond coating and tested in 100 h cycles in air + 10%H2O at 1100 °C. With an HVOF bond coating, initial results indicate that 12.5 mm diameter rod specimens have much shorter 100 h cycle lifetimes than disk specimens. Much longer lifetimes were obtained when the bond coating had an inner HVOF layer and outer APS layer.

scholarly journals A Comparative Study on the Synthesis and Properties of Yttria Stabilized Zirconia (YSZ) and Lanthana Doped YSZ Plasma Sprayed Thermal Barrier Coatings

2013 ◽  
Author(s):  
S. T. Aruna ◽  
N. Balaji ◽  
B. Arul Paligan
Keyword(s):  
Thermal Conductivity ◽  
Thermal Barrier Coatings ◽  
Gas Turbines ◽  
Operating Temperature ◽  
Yttria Stabilized Zirconia ◽  
Thermal Barrier ◽  
Spray Parameters ◽  
Stabilized Zirconia ◽  
Barrier Coatings ◽  
Plasma Sprayed

Ceramic thermal barrier coatings (TBCs) have been used for decades to extend the life of combustors and high temperature turbine stationary and rotating components to increase the operating temperature and in turn the performance of gas turbines or diesel engines can be increased. At present, thermal barrier coatings (TBCs) of Y2O3 partially stabilized ZrO2 (YSZ) films are widely used. In recent years ceramic compositions useful in thermal barrier coatings having reduced thermal conductivity are being explored to further increasing the operating temperature of gas turbines and improve the engine efficiency. In the present study, a comparison of the properties of state-of-the art 8wt% yttria stabilized zirconia (YSZ) and lanthana doped YSZ plasma sprayed coatings is presented. Plasma sprayable powders were prepared in the laboratory by a single step precipitation method and characterized. Both the powders had good flowability. These powders were plasma sprayed at identical critical plasma spray parameters. The coatings were characterized for phase, microstructure and thermal conductivity. Both the powders and coatings exhibited tetragonal form of zirconia and no traces of lanthana were observed. Both the coatings exhibited similar porosity levels. Microstructure of the coatings revealed porous coating with good adhesion of the bondcoat with the topcoat. Plasma sprayed 8wt% YSZ and lanthana doped YSZ exhibited thermal conductivity values of 0.88 and 0.67 W m−1 K−1 respectively which is lower than that reported in literature. This study shows that lanthana doping in YSZ helps in lowering the thermal conductivity and hence this coating may be a potential candidate for TBC application.

An Investigation on Hot Corrosion Resistance of Plasma Sprayed Composite YSZ-Gd2Zr2O7 and Gd2Zr2O7 Thermal Barrier Coatings in Simulated Turbine Environment at 1050°C

2012 ◽  
Author(s):  
M. H. Habibi ◽  
Li Wang ◽  
Shengmin Guo
Keyword(s):  
Corrosion Resistance ◽  
Composite Coating ◽  
Thermal Barrier Coatings ◽  
Hot Corrosion ◽  
Gas Turbines ◽  
Chemical Interaction ◽  
Thermal Barrier ◽  
X Ray Diffraction ◽  
Barrier Coatings ◽  
Plasma Sprayed

Thermal barrier coatings (TBCs) are frequently used on hot section components in gas turbines. Rare-earth zirconate ceramics used as thermal barrier coatings have attracted increasing interest in recent years due to their distinctly lower thermal conductivity than common TBC material; Yttria stabilized zirconia (YSZ). This paper investigates the hot corrosion resistance of composite YSZ+Gd2Zr2O7 and Gd2Zr2O7 coating, in Na2SO4+V2O5 at 1050°C. Chemical interaction is found to be the major corrosive mechanism for the deterioration of these coatings. Characterizations using X-ray diffraction (XRD) and scanning electron microscope (SEM) indicate that the reaction between NaVO3 and Y2O3 in YSZ produces YVO4 and leads to the transformation of tetragonal ZrO2 to monoclinic ZrO2. Then For the Gd2Zr2O7+YSZ composite coating, by the formation of GdVO4, the amount of YVO4 formed on the YSZ+Gd2Zr2O7 composite coating is significantly reduced, thus the amount of monoclinic phase in the TBC coating is substantially reduced. Comparing to YSZ, under a high temperature of 1050°C, Gd2Zr2O7 is more stable, both thermally and chemically, So Gd2Zr2O7 exhibits a better hot corrosion resistance than YSZ+Gd2Zr2O7 composite coating.

Near Infrared Radiative Properties of Thermal Barrier Coatings

2021 ◽  
Author(s):  
Yao Wang ◽  
Pei-feng Hsu ◽  
Yingsang Wu
Keyword(s):  
Heat Transfer ◽  
Gas Turbine ◽  
Thermal Barrier Coatings ◽  
Near Infrared ◽  
Radiative Heat ◽  
Radiative Properties ◽  
Thermal Barrier ◽  
Air Plasma ◽  
Barrier Coatings ◽  
Plasma Sprayed

Abstract Thermal barrier coatings are widely used in gas turbines to protect the gas turbine metal components against very high combustion product temperature. To improve energy efficiency, higher combustion temperatures are needed. A limiting factor at present is the stability under extreme and prolonged heating of thermal barrier coatings. The coatings are typically made by the air plasma sprayed process in which fine particles of yttria-stabilized zirconia (YSZ) are melted or partially melted and ejected from plasma jet at high speed onto the bond coated substrate metal. With increasing combustion temperature and pressure in the modern gas turbine engines radiative heat transfer is becoming an important portion of the overall heat transfer in the thermal barrier coating. This study has demonstrated that the commonly used Kubelka-Munk method in the radiative property reduction from the measured transmittance and reflectance spectra of YSZ coatings will incur inaccurate result when the coating optical thickness is not sufficiently large. An alternative method — the discrete ordinates method with the asymmetric spherical ring angular quadrature — is used instead. The absorption and scattering coefficients of air plasma sprayed YSZ films are determined over the wavelength range from 1 to 2.6 μm at room temperature. Over this near infrared wavelength range, the scattering coefficient decreases with the increasing wavelength and the absorption coefficient is very small overall. The pore size distributions before and after the 50-hr temperature gradient, thermal cycling are compared. The sintering effect as well as the crack growth will impact the coating radiative properties. These results point to a clear need for better understanding of the radiative heat transfer process, which includes the microstructure-property relationship, progressive changes of the radiative properties with the operation condition and time.

Microstructure-Based Life Prediction of Thermal Barrier Coatings

2013 ◽  
Vol 592-593 ◽  
pp. 413-416 ◽  
Author(s):  
Robert Eriksson ◽  
Kang Yuan ◽  
Sten Johansson ◽  
Ru Lin Peng
Keyword(s):  
Thermal Barrier Coatings ◽  
Gas Turbines ◽  
Life Prediction ◽  
Prediction Models ◽  
Atmospheric Plasma ◽  
Thermal Barrier ◽  
Barrier Coatings ◽  
Al Content ◽  
Β Phase ◽  
Plasma Sprayed

The widespread use of thermal barrier coatings (TBC) in gas turbines stresses the importance of accurate life prediction models for TBCs. During service, the TBC may fail due to thermal fatigue or through the formation of thermally grown oxides (TGOs). The current paper presents a Thermo-Calc/Dictra-based approach to life prediction of isothermally oxidised atmospheric plasma sprayed (APS) TBCs. The β-phase depletion of the coating was predicted and compared to life prediction criteria based on TGO thickness and Al content in the coating. All tried life models underestimated the life of the coating where the β-depletion-based model was the most conservative.

Sign in / Sign up

Export Citation Format

Share Document