scholarly journals Evaluation of Commercial Coatings on MarM-002, IN-939 and CM-247 Substrates

1996 ◽  
Author(s):  
J. G. Goedjen ◽  
G. P. Wagner
Keyword(s):  
Electron Beam ◽  
Vapor Deposition ◽  
Bond Coat ◽  
Physical Vapor Deposition ◽  
Thermally Grown Oxide ◽  
Department Of Energy ◽  
Superior Performance ◽  
Air Plasma ◽  
Bond Coats ◽  
Plasma Sprayed

As part of the U.S. Department of Energy Advanced Turbine Systems Program, the performance of Chromalloy RT122, RT122 over RT69 and the Howmet 150L bond coats were evaluated for use in the next generation of Westinghouse combustion turbines. Air plasma sprayed and electron beam physical vapor deposition 8% yttria stabilized zirconia thermal barrier coatings were applied to the bond coats. The coating systems were evaluated in air at 2102°F (1150°C), cooling to room temperature once per day. The life-limiting failure mode in both air plasma sprayed (APS) and electron beam - physical vapor deposition (EB-PVD) coating systems is the oxidation of the bond coat. The coating life is related to the growth rate and morphology of the thermally grown oxide. The superior performance of RT122 on MarM-002, the duplex bond coat system of RT122 over RT69 on MarM-002 and Howmet 150L on MarM-002 can be related to the development of a uniform, slow growing oxide scale. The development of a non-uniform oxidation front contributes to the reduced life of RT122 on IN-939 and CM-247.

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.

NONDESTRUCTIVE IMPEDANCE SPECTROSCOPY EVALUATION OF THE BOND COAT OXIDATION IN THERMAL BARRIER COATINGS

2007 ◽  
Vol 14 (05) ◽  
pp. 935-943 ◽  
Author(s):  
L. YANG ◽  
Y. C. ZHOU ◽  
W. G. MAO ◽  
Q. X. LIU
Keyword(s):  
Impedance Spectroscopy ◽  
Thermal Barrier Coatings ◽  
Bond Coat ◽  
Equivalent Circuit Model ◽  
Isothermal Oxidation ◽  
Thermally Grown Oxide ◽  
Thermal Barrier ◽  
Air Plasma ◽  
Barrier Coatings ◽  
Plasma Sprayed

In this paper, the impedance spectroscopy technique was employed to examine nondestructively the isothermal oxidation of air plasma sprayed (APS) thermal barrier coatings (TBCs) in air at 800°C. Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) were also used to characterize the microstructure evolution of TBCs. After oxidation, the thermally grown oxide (TGO), which was mainly composed of alumina as confirmed by EDX, formed at the upper ceramic coat/bond coat interface, the lower bond coat/substrate interface, and the bond coat. Impedance diagrams obtained from impedance measurements at room temperature were analyzed according to the equivalent circuit model proposed for the TBCs. Various observed electrical responses relating to the growth of oxides and the sintering of YSZ were explained by simulating the impedance spectra of the TBCs.

Delamination toughness of electron beam physical vapor deposition (EB-PVD) Y2O3–ZrO2 thermal barrier coatings by the pushout method: Effect of thermal cycling temperature

2008 ◽  
Vol 23 (9) ◽  
pp. 2382-2392 ◽  
Author(s):  
M. Tanaka ◽  
Y.F. Liu ◽  
S.S. Kim ◽  
Y. Kagawa
Keyword(s):  
Electron Beam ◽  
Thermal Cycling ◽  
Bond Coat ◽  
Physical Vapor Deposition ◽  
Thermally Grown Oxide ◽  
Test Method ◽  
Thermal Barrier ◽  
Barrier Coating ◽  
Delamination Toughness ◽  
Cycling Temperature

A pushout test method was used to quantify effect of thermal cycling temperatures on the delamination toughness of an electron beam physical vapor deposited thermal barrier coating (EB-PVD TBC). The delamination toughness, Γi, was related to the maximum thermal cycling temperature, Th, equal to 1000, 1025, 1050, and 1100 °C. The measured delamination toughness varied from 9 to 95 J/m2. At Th = 1000 °C, Γi attained a maximum value, larger than that of the as-deposited sample and decreasing with increased Th. During the thermal cycling tests, the thermally grown oxide (TGO) was formed between the TBC and the bond coat deposited onto the superalloy substrate. Inside the TGO layer, mixture of Al2O3 and ZrO2 oxides was observed close to the TBC side with nearly pure Al2O3 phases close to the bond-coat side. During the pushout test, delamination occurred at the interface of the mixture and pure Al2O3 layer with an exception for Th = 1100 °C specimens where delamination also occurred at the interface between the TGO and bond-coat layers. The effect of thermal cycling temperatures on the delamination toughness is discussed in terms of the microstructural change and delamination behavior.

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.

scholarly journals Isothermal Oxidation Behavior of Gadolinium Zirconate (Gd2Zr2O7) Thermal Barrier Coatings (TBCs) produced by Electron Beam Physical Vapor Deposition (EB-PVD) technique

2018 ◽  
Vol 16 (1) ◽  
pp. 986-991 ◽  
Author(s):  
Kadir Mert Doleker ◽  
Yasin Ozgurluk ◽  
Hayrettin Ahlatci ◽  
Abdullah Cahit Karaoglanli
Keyword(s):  
Electron Beam ◽  
Thermal Barrier Coatings ◽  
Vapor Deposition ◽  
Bond Coat ◽  
Physical Vapor Deposition ◽  
Isothermal Oxidation ◽  
Atmospheric Plasma ◽  
Thermal Barrier ◽  
Barrier Coatings ◽  
X Ray

AbstractThermal Barrier Coatings (TBCs) provide thermal insulation for gas turbine components operating at high temperatures. Generally, TBCs were produced on a MCrAlY bond coat with 7-8% Yttria Stabilized Zirconia (YSZ) using Atmospheric Plasma Spray (APS) technique. In this study, Inconel 718 substrate material was coated with CoNiCrAlY bond coat using high velocity oxygen fuel (HVOF) technique. Afterward, Gd2Zr2O7 was deposited on samples using Electron Beam Physical Vapor Deposition (EB-PVD) technique. Produced TBCs were exposed to isothermal oxidation tests at 1000°C for 8 h, 24 h, 50 h and 100 h in muffle furnace. Scanning electron microscopy-energy distribution X-ray (SEM-EDX) spectroscopy was used to investigate thermally grown oxide (TGO) layer and TGO growth behavior of TBCs. In addition, X-ray Diffractometer (XRD) analysis was performed to TBCs to understand whether phase transformation occurs or not before and after oxidation.

Influence of Processing on Microstructure and Performance of Electron Beam Physical Vapor Deposition (EB-PVD) Thermal Barrier Coatings

2002 ◽  
Vol 124 (2) ◽  
pp. 229-234 ◽  
Author(s):  
U. Schulz ◽  
K. Fritscher ◽  
C. Leyens ◽  
M. Peters
Keyword(s):  
Electron Beam ◽  
Vapor Deposition ◽  
Physical Vapor Deposition ◽  
Processing Parameters ◽  
Columnar Structure ◽  
Thermally Grown Oxide ◽  
Thermal Barrier ◽  
Barrier Coating ◽  
And Performance ◽  
Microstructure And Performance

The paper addresses the effect of processing parameters on microstructure and lifetime of electron beam physical vapor deposition, partially yttria-stabilized zirconia (EB-PVD PYSZ) coatings deposited onto NiCoCrAlY-coated Ni-base superalloys. In particular, the formation of a thermally grown oxide layer, an equi-axed zone, and various columnar arrangements of the highly textured PYSZ layers are discussed with respect to processing conditions. Three different microstructures were cyclically tested at 1100°C. The intermediate columnar structure was superior with respect to cyclic life times to a fine and to a coarse columnar structure which was mainly attributed to differences in the elastic properties. The effect of PYSZ microstructure on hot corrosion behavior of the thermal barrier coating (TBC) system at 950°C is briefly discussed.

A Comparative Study of Two-Layer NiAl Bond Coat TBC and its Failure Mechanism

2007 ◽  
Vol 336-338 ◽  
pp. 1770-1772
Author(s):  
He Fei Li ◽  
Zhao Hui Zhou ◽  
Hesnawi A ◽  
Kuo Jiang ◽  
Sheng Kai Gong
Keyword(s):  
Electron Beam ◽  
Comparative Study ◽  
Thermal Cycling ◽  
Failure Mechanism ◽  
Thermal Barrier Coatings ◽  
Vapor Deposition ◽  
Bond Coat ◽  
Physical Vapor Deposition ◽  
Thermal Barrier ◽  
Barrier Coatings

Thermal barrier coatings with one-layered/ two-layered NiAl bond coat were produced by electron beam physical vapor deposition (EB-PVD). Compared to the TBC with one-layered bond coat, the TBC with two-layered bond coat improved the thermal cycling resistance significantly. The failure mechanism of the two-layer NiAl bond coat TBC was investigated in this paper.

scholarly journals The Effects of High Temperature Exposure on the Durability of Thermal Barrier Coatings

2000 ◽  
Author(s):  
N. M. Yanar ◽  
M. J. Stiger ◽  
F. S. Pettit ◽  
G. H. Meier
Keyword(s):  
Electron Microscopy ◽  
Bond Coat ◽  
Physical Vapor Deposition ◽  
Thermally Grown Oxide ◽  
Phase Changes ◽  
Cross Sectional ◽  
Outward Diffusion ◽  
Bond Coats ◽  
Platinum Aluminide ◽  
Temperature Exposure

Abstract Yttria-stabilized Zirconia (YSZ) coatings deposited by electron beam physical vapor deposition on platinum aluminide and NiCoCrAlY bond coats on single crystal superalloy substrates have been oxidized at temperatures between 1000 and 1200°C in air. The cyclic oxidation lives of the systems with platinum aluminide bond coats were substantially longer than those with NiCoCrAlY bond coats. The thermally grown oxide (TGO) that develops between the bond coat and the TBC during oxidation, as well as the bond coat and the TBC adjacent to the TGO, have been examined in detail using optical metallography, scanning electron microscopy (SEM), and cross-sectional transmission electron microscopy (XTEM). The YSZ is observed to undergo significant amounts of sintering. The TGO grows by the inward diffusion of oxygen and the outward diffusion of aluminum. In some cases, the outward growth component incorporates some of the TBC into the TGO. The depletion of aluminum results in phase changes in the bond coats. Failure of the TBCs occurs after fixed amounts of oxidation which result in increasing amounts of elastic energy being stored in the TGO and YSZ as well as degradation of the TGO-bond coat interface. The fracture path changed as a function of exposure time and temperature with larger amounts of separation occurring at the TGO/BC interface for higher temperatures and longer exposures in dry air. Failure can be accelerated in the presence of water vapor, particularly if spinel formation is induced. Fracture occurs primarily in the oxides, in this case. The fracture surface for systems with platinum aluminide bond coats often contains precipitates, which are rich in refractory metals. These features do not appear to be prevalent with NiCoCrAlY bond coats.

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