On TGO creep and the initiation of a class of fatigue cracks in thermal barrier coatings

Hernandez, Mercedes T.; Karlsson, Anette M.; Bartsch, Marion

doi:10.1016/j.surfcoat.2009.05.018

Cited by 42 publications

(18 citation statements)

References 24 publications

(75 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The simplified TBC model takes into account three layers, namely, the TGO layer, a BC, and the super alloy substrate. The TGO layer is divided into two sublayers: an alumina layer adjacent to the BC and a MZ above it [11]. An initial alumina layer and an initial MZ layer are constructed to model oxidation during the spraying process.…”

Section: Finite Element Modelmentioning

confidence: 99%

“…Their work helps clarify the failure mechanism due to microstructural changes caused by chemical reactions between the related elements. Hernandez et al [11] studied TGO creep and the initiation of a class of fatigue cracks in TBCs using a thermal gradient mechanical fatigue test. In their study, they considered the MZ as a part of TGO layer and examined and quantified the thermomechanical performance of TGO through a finite element (FE) modelling method.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Effects of a Mixed Zone on TGO Displacement Instabilities of Thermal Barrier Coatings at High Temperature in Gas-Cooled Fast Reactors

Wang¹,

Ding

Song³

et al. 2016

Science and Technology of Nuclear Installations

View full text Add to dashboard Cite

Thermally grown oxide (TGO), commonly pure α-Al2O3, formed on protective coatings acts as an insulation barrier shielding cooled reactors from high temperatures in nuclear energy systems. Mixed zone (MZ) oxide often grows at the interface between the alumina layer and top coat in thermal barrier coatings (TBCs) at high temperature dwell times accompanied by the formation of alumina. The newly formed MZ destroys interface integrity and significantly affects the displacement instabilities of TGO. In this work, a finite element model based on material property changes was constructed to investigate the effects of MZ on the displacement instabilities of TGO. MZ formation was simulated by gradually changing the metal material properties into MZ upon thermal cycling. Quantitative data show that MZ formation induces an enormous stress in TGO, resulting in a sharp change of displacement compared to the alumina layer. The displacement instability increases with an increase in the MZ growth rate, growth strain, and thickness. Thus, the formation of a MZ accelerates the failure of TBCs, which is in agreement with previous experimental observations. These results provide data for the understanding of TBC failure mechanisms associated with MZ formation and of how to prolong TBC working life.

show abstract

Section: Finite Element Modelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Effects of a Mixed Zone on TGO Displacement Instabilities of Thermal Barrier Coatings at High Temperature in Gas-Cooled Fast Reactors

Wang¹,

Ding

Song³

et al. 2016

Science and Technology of Nuclear Installations

View full text Add to dashboard Cite

show abstract

“…Studies have shown that increasing tensile loads can cause cracks to propagate perpendicularly from the bond coat/TGO interface 3 , whereas under low applied tensile loads delamination is dominating failure behavior 4 . Additionally, combinations of thermally grown oxide (TGO) growth stress, applied tensile axial loading and creep relaxation of the TGO has been shown to initiate these cracks under TGMF loading conditions 5 .…”

Section: Introductionmentioning

confidence: 99%

Synchrotron XRD Measurements of Thermal Barrier Coatings Subjected to Loads Representing Operational Conditions of Rotating Gas Turbine Blades

Knipe

Manero

Siddiqui

et al. 2014

52nd Aerospace Sciences Meeting

Self Cite

View full text Add to dashboard Cite

High-energy synchrotron x-rays were used in this work to monitor the internal strain behavior of Thermal Barrier Coatings (TBC) under thermal gradient and mechanical loading. Tubular specimens made from Nickel based super alloy with a TBC-system applied onto the outer surface by Electron Beam Physical Vapor Deposition were used to allow for cooling of the internal surface of the substrate while heating the external surface during thermal mechanical cycling. The coating system consisted of a Yittria Stabilized Zirconia (YSZ) top coat and a MCrAlY bond coat. Through transmission along with a 2D detector allowed for the 2D strain monitoring of each layer during high temperature operation. Monitoring the micro-strain of each phase within the layers provides insight into their high temperature behavior which can be used to further develop predictive models including evolution of elastic strain as well as creep and plasticity. Obtained results have shown a large variation in strains during ramp up of in-phase thermal and/or mechanical load with a significant tensile strain mismatch between the two prominent phases of the bond coat. The YSZ has displayed residual compressive strains at the bond coat/YSZ interface and maintained some compressive residual strain during high temperature holds. These results give valuable insight into the mechanics of these complex systems under various high temperature conditions.

show abstract

“…8 Along with simulation studies, results have shown that a combination of the Thermally Grown Oxide (TGO) growth stress, applied tensile axial loading and creep relaxation of the TGO, leads to the initiation of these cracks under TGMF loading conditions. 9 The difficulty associated with maintaining a thermal gradient in cylindrical samples that effectively simulates the operational conditions has been addressed previously for TGMF testing using quartz lamps and controlled coolant flow. 6 Integral to the understanding of failure mechanisms in these layered systems is the strain evolution to failure under the different thermal and mechanical loading conditions.…”

Section: Introductionmentioning

confidence: 99%

Synchrotron X-ray measurement techniques for thermal barrier coated cylindrical samples under thermal gradients

Siddiqui

Knipe

Manero

et al. 2013

Review of Scientific Instruments

Self Cite

View full text Add to dashboard Cite

Measurement techniques to obtain accurate in situ synchrotron strain measurements of thermal barrier coating systems (TBCs) applied to hollow cylindrical specimens are presented in this work. The Electron Beam Physical Vapor Deposition coated specimens with internal cooling were designed to achieve realistic temperature gradients over the TBC coated material such as that occurring in the turbine blades of aeroengines. Effects of the circular cross section on the x-ray diffraction (XRD) measurements in the various layers, including the thermally grown oxide, are investigated using high-energy synchrotron x-rays. Multiple approaches for beam penetration including collection, tangential, and normal to the layers, along with variations in collection parameters are compared for their ability to attain high-resolution XRD data from the internal layers. This study displays the ability to monitor in situ, the response of the internal layers within the TBC, while implementing a thermal gradient across the thickness of the coated sample. The thermal setup maintained coating surface temperatures in the range of operating conditions, while monitoring the substrate cooling, for a controlled thermal gradient. Through variation in measurement location and beam parameters, sufficient intensities are obtained from the internal layers which can be used for depth resolved strain measurements. Results are used to establish the various techniques for obtaining XRD measurements through multi-layered coating systems and their outcomes will pave the way towards goals in achieving realistic in situ testing of these coatings.

show abstract

On TGO creep and the initiation of a class of fatigue cracks in thermal barrier coatings

Cited by 42 publications

References 24 publications

Effects of a Mixed Zone on TGO Displacement Instabilities of Thermal Barrier Coatings at High Temperature in Gas-Cooled Fast Reactors

Effects of a Mixed Zone on TGO Displacement Instabilities of Thermal Barrier Coatings at High Temperature in Gas-Cooled Fast Reactors

Synchrotron XRD Measurements of Thermal Barrier Coatings Subjected to Loads Representing Operational Conditions of Rotating Gas Turbine Blades

Synchrotron X-ray measurement techniques for thermal barrier coated cylindrical samples under thermal gradients

Contact Info

Product

Resources

About