The influence of bond coat surface roughness on chemical failure and delamination in TBC systems

2008 ◽  
Vol 59 (6) ◽  
pp. 508-513 ◽  
Author(s):  
M. P. Taylor ◽  
W. M. Pragnell ◽  
H. E. Evans
Keyword(s):  
Surface Roughness ◽  
Bond Coat ◽  
Chemical Failure ◽  
Tbc Systems

A Novel Duplex Re-NiW Based Diffusion Barrier on a Nickel-Base Superalloy for TBC Systems

2008 ◽  
Vol 595-598 ◽  
pp. 127-134 ◽  
Author(s):  
Sebastien Mercier ◽  
Denis Boivin ◽  
Marie Pierre Bacos ◽  
Pierre Josso
Keyword(s):  
Diffusion Barrier ◽  
Bond Coat ◽  
Alloying Elements ◽  
Nickel Base Superalloy ◽  
Coating Process ◽  
Thermal Treatments ◽  
Eds Analysis ◽  
Nickel Base ◽  
Tbc Systems ◽  
Base Superalloy

A diffusion barrier between a 4th generation superalloy (MC-NG) and a β-(Ni, Pt)Al has been studied. The used coating process combines Re and NiW electrolytic deposits followed by thermal treatments. The diffusion barrier is composed of a continuous 3 &m thick ReWNi layer under a 10 &m thick β-(Ni, Pt)Al containing W rich precipitates. EDS analysis on as coated samples and on 50h-1100°C-Ar aged samples showed that the Re-NiW layer works as a diffusion barrier. The Al reservoir in the bond coat after aging is higher with the diffusion barrier than without. The concentrations of alloying elements are also lower in the bond coat with the diffusion barrier than without.

Oxygen Transport Through the Zirconia Top Coat in Thermal Barrier Coating Systems

1998 ◽  
Author(s):  
A.C. Fox ◽  
T.W. Clyne
Keyword(s):  
Thermal Barrier Coating ◽  
Bond Coat ◽  
Ionic Conduction ◽  
Gas Permeability ◽  
Gas Permeation ◽  
Thermal Barrier ◽  
Barrier Coating ◽  
Oxygen Gas ◽  
Plasma Sprayed ◽  
Tbc Systems

Abstract The gas permeability of plasma sprayed yttria-stabilised zirconia coatings has been measured over a range of temperature, using hydrogen and oxygen gas. The permeability was found to be greater for coatings produced with longer stand-off distances, higher chamber pressures and lower torch powers. Porosity levels have been measured using densitometry and microstructural features have been examined using SEM. A model has been developed for prediction of the permeability from such microstructural features, based on percolation theory. Agreement between predicted and measured permeabilities is good. Ionic conduction through the coatings has also been briefly explored. It is concluded that transport of oxygen through the top coat in thermal barrier coating (TBC) systems, causing oxidation of the bond coat, occurs primarily by gas permeation rather than ionic conduction, at least up to temperatures of about 1000°C and probably up to higher temperatures. Top coat permeabilities appreciably below those measured will be required if the rate of bond coat oxidation is to be reduced by cutting the supply of oxygen to the interface.

Oxidation characteristics of a platinized MCrAlY bond coat for TBC systems during cyclic oxidation at 1000 °C

2005 ◽  
Vol 199 (1) ◽  
pp. 77-82 ◽  
Author(s):  
W.J. Quadakkers ◽  
V. Shemet ◽  
D. Sebold ◽  
R. Anton ◽  
E. Wessel ◽  
...  
Keyword(s):  
Bond Coat ◽  
Cyclic Oxidation ◽  
Oxidation Characteristics ◽  
Tbc Systems

Modeling Effects of Material Properties and Three-Dimensional Surface Roughness on Thermal Barrier Coatings

2000 ◽  
Vol 645 ◽  
Author(s):  
Michael L. Glynn ◽  
K.T. Ramesh ◽  
P.K. Wright ◽  
K.J. Hemker
Keyword(s):  
Surface Roughness ◽  
Residual Stresses ◽  
Thermal Barrier Coatings ◽  
Material Properties ◽  
Bond Coat ◽  
Coefficient Of Thermal Expansion ◽  
Three Dimensional ◽  
Thermal Barrier ◽  
Barrier Coatings ◽  
Dimensional Surface

ABSTRACTThermal barrier coatings (TBCs) are known to spall as a result of the residual stresses that develop during thermal cycling. TBC's are multi-layered coatings comprised of a metallic bond coat, thermally grown oxide and the ceramic top coat, all on top of a Ni-base superalloy substrate. The development of residual stresses is related to the generation of thermal, elastic and plastic strains in each of the layers. The focus of the current study is the development of a finite element analysis (FEA) that will model the development of residual stresses in these layers. Both interfacial roughness and material parameters (e.g., modulus of elasticity, coefficient of thermal expansion and stress relaxation of the bond coat) play a significant role in the development of residual stresses. The FEA developed in this work incorporates both of these effects and will be used to study the consequence of interface roughness, as measured in SEM micrographs, and material properties, that are being measured in a parallel project, on the development of these stresses. In this paper, the effect of an idealized three-dimensional surface roughness is compared to residual stresses resulting from a grooved surface formed by revolving a sinusoidal wave about an axis of symmetry. It is shown that cylindrical and flat button models give similar results, while the 3-D model results in stresses that are significantly larger than the stresses predicted in 2-D.

Influence of Martensitic Transformation on the Durability of TBC Systems (Invited)

Aerospace ◽  
2003 ◽  
Author(s):  
M. W. Chen ◽  
M. L. Glynn ◽  
D. Pan ◽  
K. T. Ramesh ◽  
K. J. Hemker ◽  
...  
Keyword(s):  
High Temperature ◽  
Thermal Cycling ◽  
Bond Coat ◽  
Transformation Strain ◽  
Xrd Analysis ◽  
Heating And Cooling ◽  
Β Phase ◽  
Transmission Electron ◽  
High Temperature Xrd ◽  
Tbc Systems

Microstructural evolution of bond coat with thermal cycling was characterized with transmission electron microscopy (TEM) and high temperature X-ray diffraction (HT-XRD) analysis. Before thermal cycling, the structure of asfabricated bond coat was confirmed to be a long-range ordered B2 β-phase. After thermal cycling to ∼28% of the cyclic life, the bond coat was found to transform into a Nirich L10 martensite (M) from its original B2 structure. The transformations, M ↔ B2, were demonstrated to be reversible and to occur on heating and cooling in each cycle. Quantitative high temperature XRD measurements verified the phase transformations produce about 0.7 % transformation strain. Finite element calculations incorporating the transformation strain indicate that the mertensitic transformation significantly influences the development of stresses and strains in TBC systems.

scholarly journals Microstructure and lifetime of Hf or Zr doped sputtered NiAlCr bond coat/7YSZ EB-PVD TBC systems

2018 ◽  
Vol 335 ◽  
pp. 41-51 ◽  
Author(s):  
J. Muñoz Saldaña ◽  
U. Schulz ◽  
G.C. Mondragón Rodríguez ◽  
L.A. Caceres-Diaz ◽  
H. Lau
Keyword(s):  
Bond Coat ◽  
Tbc Systems

Fracture Behavior of Plasma-Sprayed Thermal Barrier Coatings with Different Bond Coats upon Cyclic Thermal Exposure

2009 ◽  
Vol 620-622 ◽  
pp. 343-346
Author(s):  
Young Seok Sim ◽  
Sung Il Jung ◽  
Jae Young Kwon ◽  
Je Hyun Lee ◽  
Yeon Gil Jung ◽  
...  
Keyword(s):  
Bond Coat ◽  
Fracture Behavior ◽  
Thermal Exposure ◽  
Thermally Grown Oxide ◽  
Fatigue Tests ◽  
Thermal Barrier ◽  
Air Plasma ◽  
Bond Coats ◽  
Barrier Coating ◽  
Tbc Systems

The effects of bond coat nature in thermal barrier coating (TBC) systems on the delamination or fracture behavior of the TBCs with different bond coats prepared using two different processes—air plasma spray (APS) and high velocity oxyfuel (HVOF)—were investigated by cyclic thermal fatigue tests. The TBCs with the HVOF bond coat were delaminated or fractured after 3–6 cycles, whereas those with the APS bond coat were delaminated after 10 cycles or show a sound condition. These results indicate that the TBC system with the APS bond coat has better thermal durability than the system with the HVOF bond coat under long-term cyclic thermal exposure. The hardness values of the TBCs (top coats) in both systems are dependent on applied loads, irrespective of the hardness of the bond coats and the substrate. The values are not responded to the bond coat nature or the exposure time. Thermally grown oxide (TGO) layers in both cases consist of two regions with the inner TGO layer containing only Al2O3 and the outer TGO layer of mixed-oxide zone containing Ni, Co, Cr, Al in Al2O3 matrix. The outer TGO layer has a more irregular shape than the inner TGO layer, and there are many pores within the outer layer. At failure, the TGO thickness of the TBC system with the HVOF bond coat is 9–13 m, depending on the total exposed time, and that of the TBC system with the APS bond coat is about 20 m. The both TBC systems show the diffusion layer on the side of substrate in the interface between the bond coat and the substrate. The relationship between the delamination or fracture behavior and the bond coat nature has been discussed, based on the elemental analysis and microstructural evaluation.

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