Effect of TGO thickness, Pores, and Creep on the Developed Residual Stresses in Thermal Barrier Coatings under Cyclic Loading using SEM Image-Based Finite Element Model

2021 ◽  
Author(s):  
Ahmed Abdelgawad ◽  
Khaled Al-Athel
Keyword(s):  
Finite Element ◽  
Cyclic Loading ◽  
Residual Stresses ◽  
Finite Element Model ◽  
Thermal Barrier Coatings ◽  
Element Model ◽  
Thermal Barrier ◽  
Barrier Coatings ◽  
Sem Image

scholarly journals Finite element simulation of residual stresses and failure mechanism of plasma sprayed thermal barrier coatings considering real interface

2021 ◽  
Author(s):  
Khaled Al-Athel ◽  
Keyword(s):  
Finite Element ◽  
Thermal Barrier Coatings ◽  
Crack Nucleation ◽  
Element Model ◽  
Thermal Barrier ◽  
Inlet Temperature ◽  
Operating Cycle ◽  
Barrier Coatings ◽  
Sem Image ◽  
Plasma Sprayed

In order to increase the efficiency of gas turbine engines, which are used for propulsion and electricity generation, the turbine inlet temperature (TIT) has to be as high as possible. Using Thermal Barrier Coatings (TBC) allows the metallic internal components to operate at elevated temperature near to its melting temperature. Thermally growing oxide induces cracks formation in the top coat that may lead to complete failure TBC due to spallation. This research aims at investigating the development of the stresses and critical cites that have possibility of crack nucleation due to thermal mismatch during operating cycle of a typical plasma sprayed TBC. A true finite element model was developed based on a scanning electron microscope image taking the advantage of a commercial finite element package (ABAQUS) and image processing techniques. The model including the effect of creep on all layers and plastic deformation of BC, TGO and substrate. The results show that unlike common unit cell models in literature, a better understanding can be achieved by having a model based in an SEM image that represents the real geometry.

Investigation about Thermal Shock Property of Plasma-Spraying Sm2Zr2O7 Thermal Barrier Coatings with Different Substrate Condictions

2011 ◽  
Vol 354-355 ◽  
pp. 145-148
Author(s):  
Hong Song Zhang ◽  
Hong Chan Sun
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Thermal Expansion ◽  
Residual Stresses ◽  
Plasma Spraying ◽  
Thermal Barrier Coatings ◽  
Thermal Barrier ◽  
Shear Stresses ◽  
Substrate Thickness ◽  
Barrier Coatings

Effect of substrate conditions, including material type, thickness and radius of substrate, on thermal-shocking stresses of plasma spraying Sm2Zr2O7/ NiCrCoAlY TBCs was analyzed through finite element method. Results show that radial stresses decrease with time increasing, and they decrease with the increasing of distance from center to edge along radius. However, axial residual stresses increse abruptly at the edge of specimen. All residual stresses increse with incresing of thermal expansion coefficient of substrate. Radial stresses increase with substrate thickness increasing, however, they are not effectd by substrate thickness if it is great than 20mm.and axial residual stresses and shear stresses are not effected by the substrate thickness. The maximum values of axial stresses and shear stresses were not effected by sustrate radius. and values of radial stresses remian invariable when substrate radius is over 18mm.

Transient Residual Stresses in Thermal Barrier Coatings: Analytical and Numerical Results

1998 ◽  
Vol 65 (2) ◽  
pp. 346-353 ◽  
Author(s):  
S. Q. Nusier ◽  
G. M. Newaz
Keyword(s):  
Finite Element ◽  
Steady State ◽  
Residual Stresses ◽  
Thermal Barrier Coatings ◽  
Bond Coat ◽  
Biaxial Stress ◽  
Thermal Barrier ◽  
Processing Temperature ◽  
Barrier Coatings ◽  
State Case

Thermal barrier coatings (TBCs) provide thermal insulation to high-temperature superalloys. Residual stresses develop in TBCs during cool-down from processing temperatures due to the thermal expansion mismatch between the different layers (substrate, bond coat, and the ceramic TBC). These residual stresses can initiate microcracks at the bond coat/TBC interface which can lead to debonding at the bond coat/TBC interface. Elasticity-based modeling was used to determine the transient stresses in the TBC, bond coat, and the superalloy substrate with specific attention to the interfaces. For the steady-state case, finite element modeling was undertaken as well. Closed-form elasticity solutions correlated well with the finite element results for the steady-state case. The highest residual stresses occurred at the interface between the bond coat and the TBC. An important result of this investigation was that the TBC/bond coat interface was under biaxial stress field. An important result was that the residual stresses developed in the substrate are higher for the case of partly cooled specimen compared to the fully cooled specimen which can be rationalized due to the presence of higher temperature gradients at earlier times during cool-down from processing temperature.

Modeling and Characterization of Residual Stresses and Microstructure in Thermal Barrier Coatings after Plasma Spraying

1996 ◽  
Author(s):  
C. Persson ◽  
P. Bengtsson ◽  
J. Wigren ◽  
D. Greving
Keyword(s):  
Residual Stresses ◽  
Thermal Barrier Coatings ◽  
Thermal Stresses ◽  
Element Model ◽  
Thermal Barrier ◽  
Barrier Coatings ◽  
Bond Coating ◽  
Plasma Sprayed ◽  
Removal Technique

Abstract Thermal barrier coatings with a zirconia top coating and a NiCoCrAlY bond coating were plasma sprayed onto a nickelbase alloy. The pre-heating of the bond coated substrates and the cooling during the top coating spraying were varied to produce five different spray sets. A finite element model was developed to predict the heat transfer and the resulting thermal stresses during the spraying. A layer removal technique was used to measure the residual stresses in the as-sprayed samples. The measurements revealed low residual stresses in the top coatings and tensile stresses in the order of 150 MPa in the bond coating. A correlation between the measured top coating residual stresses and the substrate temperature in the end of the top coating spraying was found. In general, good agreement between modelled and measured residual stresses was found. The top coatings were found to contain vertical microcracks and the densities of the cracks were point-counted in the spray sets. A slight increase in microcrack densities was found as the spraying was performed onto a colder substrate. The densities of vertical microcracks were correlated to modelled in-elastic strain in the top coatings.

Simulation of the Effect of Sintering and Interface on the Failure Mechanism of Thermal Barrier Coatings

2015 ◽  
Vol 817 ◽  
pp. 764-771
Author(s):  
Wei Chen ◽  
Jian Guo Zhu ◽  
Gui Lan Chai
Keyword(s):  
Finite Element ◽  
Failure Mechanism ◽  
Thermal Barrier Coatings ◽  
Bond Coat ◽  
Great Influence ◽  
Element Model ◽  
Thermal Barrier ◽  
Barrier Coatings ◽  
Cooling Stage ◽  
The Finite Element Model

Thermal barrier coatings (TBC) are mainly composed of four layers: top coat (TC), thermal barrier oxidation (TGO), bond coat (BC) and substrate (SUB). The finite element model is used to investigate the failure mechanism of TBC. The influences of sintering of TC and the properties of TGO/BC interface on the stress S22 were considered. The numerical results show that sintering of TC can change the tendency of the stress S22 within TC from peak to valley along the TC/TGO interface; When considering the cohesive behavior of TGO/BC interface, the TGO/BC interface may begin to crack in the heating stage, then in the swelling stage the interface crack in the TGO/BC interface may close, and in the cooling stage the interface will crack again along the TGO/BC interface. When considering TGO/BC interface and sintering of TC simultaneously, sintering of TC has great influence on the stress S22 of BC near the peak and valley of TGO/BC interface.

Analysis of the Stress State in Thermal Barrier Coatings during a Thermal Cycle

1996 ◽  
Author(s):  
G. Jönsson ◽  
C. Persson
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Stress State ◽  
Residual Stresses ◽  
Thermal Barrier Coatings ◽  
Thermal Cycle ◽  
Thermal Stresses ◽  
Thermal Barrier ◽  
Barrier Coatings ◽  
Element Method

Abstract Thermal barriers made up by a ceramic top coating and a metallic bond coating are subjected to thermal cycles in service. The thermal stresses vary during the cycles and the residual stresses change as a result of plastic flow and creep. The stress state in thermal barrier coatings during a thermal cycle has been examined with a finite element method using temperature dependent material data. The calculated results were verified by measurements of the residual stresses with the layer removal technique before and after cycling of specimens heated in furnace with air environment. According to the simulation of a thermal cycle to 700 ° C, using a finite element method, the bond coat is approximately stress free after 1 hour dwell time. Thus, the residual stresses after a thermal cycle is a result of thermal expansion mismatch and temperature drop.

Effect of Substrate Condictions on Thermal Shock Property of Plasma-Spraying Sm2Zr2O7 /YSZ Thermal Barrier Coatings

2011 ◽  
Vol 332-334 ◽  
pp. 1799-1802
Author(s):  
Hong Song Zhang ◽  
Yuan Wei
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Thermal Expansion ◽  
Residual Stresses ◽  
Plasma Spraying ◽  
Thermal Barrier Coatings ◽  
Thermal Barrier ◽  
Shear Stresses ◽  
Substrate Thickness ◽  
Barrier Coatings

Effect of substrate conditions, including material type, thickness and radius of substrate, on thermal-shocking stresses of plasma spraying Sm2Zr2O7/YSZ TBCs was analyzed through finite element method. Results show that radial stresses decrease with time increasing, and they decrease with the increasing of distance from center to edge along radius. However, axial residual stresses increse abruptly at the edge of specimen. All residual stresses increse with incresing of thermal expansion coefficient of substrate. Radial stresses increase with substrate thickness increasing, however, they are not effectd by substrate thickness if it is great than 25mm.and axial residual stresses and shear stresses are not effected by the substrate thickness. The maximum values of axial stresses and shear stresses were not effected by sustrate radius. and values of radial stresses remian invariable when substrate radius is over 18mm.

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