The role of formation of continues thermally grown oxide layer on the nanostructured NiCrAlY bond coat during thermal exposure in air

2012 ◽  
Vol 261 ◽  
pp. 287-297 ◽  
Author(s):  
Mohammadreza Daroonparvar ◽  
Mohammad Sakhawat Hussain ◽  
Muhammad Azizi Mat Yajid
Keyword(s):  
Oxide Layer ◽  
Bond Coat ◽  
Thermal Exposure ◽  
Thermally Grown Oxide ◽  
Thermally Grown

Failure of a Thermal Barrier System Due to a Cyclic Displacement Instability in the Thermally grown Oxide

2000 ◽  
Vol 645 ◽  
Author(s):  
Daniel R. Mumm ◽  
Anthony G. Evans
Keyword(s):  
Bond Coat ◽  
Large Scale ◽  
Thermal Exposure ◽  
Thermally Grown Oxide ◽  
Thermal Barrier ◽  
Oxide Interface ◽  
Barrier Coating ◽  
Out Of Plane ◽  
Plane Displacement ◽  
Thermally Grown

ABSTRACTThe mechanism controlling the cyclic failure of a commercial thermal barrier system has been investigated. The system comprises an electron-beam physical vapor deposited (EB-PVD) yttria-stabilized zirconia thermal barrier coating (TBC), deposited on a (Ni Pt) Al bond coating. The thermally grown oxide (TGO) layer that forms between the TBC and bond coat at high temperature is unstable with respect to out of plane displacement, provided initial perturbations are present. With cyclic thermal exposure, the TGO displaces into the bond coat at periodic interfacial sites. The out-of-plane displacements induce strains above the TGO, normal to the interface, that cause cracking. The cracks nucleate either within the TBC layer or at the TBC/TGO interface, and extend laterally until they coalesce with cracks from other sites and coating failure occurs by large scale buckling. The TGO displacements are accommodated by visco-plastic deformation of the underlying bond coat, and are driven by a lateral component of the growth strain in the TGO. The susceptibility of the TGO to out-of-plane displacement depends critically upon the initial morphology of the metal/oxide interface. The observed material responses are compared with predictions of a ‘ratcheting’ model.

scholarly journals Growth Behavior of Thermally Grown Oxide Layer with Bond Coat Species in Thermal Barrier Coatings

2018 ◽  
Vol 55 (4) ◽  
pp. 344-351
Author(s):  
Sung Hoon Jung ◽  
Soo Hyeok Jeon ◽  
Hyeon-Myeong Park ◽  
Yeon Gil Jung ◽  
Sang Won Myoung ◽  
...  
Keyword(s):  
Oxide Layer ◽  
Thermal Barrier Coatings ◽  
Bond Coat ◽  
Thermally Grown Oxide ◽  
Growth Behavior ◽  
Thermal Barrier ◽  
Barrier Coatings ◽  
Thermally Grown

scholarly journals Thermal Cycling Induced Bond-Coat Rumpling as a Precursor to TBC Failure

2000 ◽  
Author(s):  
D. R. Clarke ◽  
V. K. Tolpygo
Keyword(s):  
Phase Transformation ◽  
Thermal Cycling ◽  
Bond Coat ◽  
Microstructural Characterization ◽  
Thermally Grown Oxide ◽  
New Model ◽  
Gamma Prime ◽  
Ni3al Phase ◽  
Thermally Grown

Abstract Microstructural observations of TBCs failed under thermal cycling conditions reveal that failure is associated with extensive local separations between either the thermally grown oxide and the TBC or within the TBC itself close to the thermally grown oxide. Based on extensive microstructural characterization and measurements of concentration profiles within the bond-coat, we present a new model for the cause of these separations based on local increases in the density of the bond coat associated with the beta-NiAl to gamma-prime Ni3Al phase transformation. The phase transformation, driven by aluminum depletion required to form the protective alumina thermally grown oxide, is constrained by the overlying TBC thereby generating tensile stresses across the TBC/TGO interface and its vicinity. The observations and evidence for the new model will be described together with the role of thermal cycling.

Determination of the Structure and Chemistry of Thermally Grown Oxides in Thermal Barrier Coatings

1999 ◽  
Vol 5 (S2) ◽  
pp. 854-855
Author(s):  
M.R. Brickey ◽  
J.L. Lee
Keyword(s):  
Thermal Barrier Coatings ◽  
Nickel Aluminide ◽  
Physical Vapor Deposition ◽  
Thermal Exposure ◽  
Thermally Grown Oxide ◽  
Thermal Barrier ◽  
Engine Operation ◽  
Barrier Coatings ◽  
Combustion Gas ◽  
Thermally Grown

Thermal barrier coatings (TBCs) insulate gas turbine hot section components from the hot (∽1200 - 1450°C) combustion gas exhaust stream. An airline company can save millions of dollars per year by using TBCs to protect vital engine components and to improve fuel efficiency. TBCs typically consist of an 8 wt.% yttria-partially-stabilized zirconia (YPSZ) ceramic topcoat deposited on a platinum-nickel-aluminide (Pt-Ni-Al) bondcoat covering a nickel-based superalloy substrate. Thermal exposure during YPSZ electron beam-physical vapor deposition (EB-PVD) and engine operation promotes the formation of a thermally grown oxide (TGO) between the Pt-Ni-Al and the YPSZ layers. Stresses can develop at the Pt-Ni-Al/TGO and TGO/YPSZ interfaces due to TGO growth and thermal expansion coefficient mismatch. These stresses eventually cause spallation of the YPSZ, leaving the metallic substrate vulnerable to high temperature degradation since exhaust temperatures are often higher than the melting temperature of most nickel-based superalloys (∽1200 - 1450°C).

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