Strain gradients in plasma-sprayed zirconia thermal barrier coatings

Scardi, Paolo; Leoni, Matteo; Bertini, Leonardo; Bertamini, L.; Cernuschi, F.

doi:10.1016/s0257-8972(98)00616-1

Cited by 29 publications

(16 citation statements)

References 7 publications

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“…There, as expected, the errors for the stresses are correspondingly high, although still tolerable, as shown in Figs. [8][9][10][11]. When scanning towards the inside of the deposit or substrate, the volume and therefore the spatial resolution increases steadily (and the error bars decrease) until the gauge volume is completely filled.…”

Section: Discussionmentioning

confidence: 99%

“…[8][9][10][11] we can state that, despite specific differences in residual stress level and gradients for the four investigated spray techniques, the residual stress profiles across the deposits or substrates show the following common features:…”

Section: Discussionmentioning

confidence: 99%

“…Compressive stresses in the deposition plane determined by a X-ray residual stress analysis in alloyed thermally sprayed deposits have been explained to be induced by plastic deformation by Iordanova and Forcey [9]. Strain gradients in plasma sprayed zirconia thermal barrier coatings have been investigated by neutron diffraction by Scardi et al [10]. Matejicek et al [11] determined stress profiles over the sample thickness in atmospheric plasma sprayed NiCrAlY deposits.…”

Section: Introductionmentioning

confidence: 99%

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Residual stress determination in thermally sprayed metallic deposits by neutron diffraction

Keller

Margadant

Pirling

et al. 2004

Materials Science and Engineering: A

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Residual stress determination in thermally sprayed metallic deposits by neutron diffraction

Keller

Margadant

Pirling

et al. 2004

Materials Science and Engineering: A

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“…The TGO affects the distribution of in-plane residual stress near the TBC/TGO interface because of its smaller CTE than the TBC. [27,34] It has been experimentally and theoretically shown [7,25,32,33] that the TBC densification, the formation process of TGO, and the thermal history, such as uniform and monotonous (aging) or temperature graded and cyclic (in-service) heating/cooling, control the distribution of residual stress in a complex fashion. Tsakalakos's group [34] has demonstrated heterogeneous through-thickness distribution of in-plane residual stress in Al 2 O 3 /TiO 2 coatings by measuring the lattice strain using a new synchrotron X-ray scattering technique.…”

Section: B Effect Of Residual Stressmentioning

confidence: 99%

Through-thickness dependence of in-plane cracking behavior in plasma-sprayed thermal barrier coatings

Zhang

Kameda

Sakurai

et al. 2005

Metall Mater Trans A

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In-plane macrocrack initiation of as-deposited, thermally aged, and in-service used thermal barrier coatings (TBCs) with different levels of pores and microcracks, affecting the Young's modulus (E c ), have been studied using a newly developed protruded TBC bending technique in conjunction with a finite-element stress analysis. In-plane macrocracking along splat boundaries initiates from a curved edge of protruded TBC under the out-of-plane and shear applied and residual stresses resolved from the in-plane components. The TBC macrocracking is characterized by the critical strain energy density [( e *) 2 /E c ], which represents the material propensity, i.e., the ratio of the interfacial cohesive energy to the critical microcrack size (␥ f /a c ), and the residual stress effect. The cracking behavior strongly depends on the type of TBC, subjected to different thermal history, and the substrate machining. Ungrooved substrate specimen tests indicate that while the as-deposited TBC has through-thickness fluctuation in ( e *) 2 /E c , the aged and used TBC exhibits a trough and peak of ( e *) 2 /E c near the middle section, respectively. In grooved or thinner substrate specimens of the TBCs where the residual stress is partially relieved, cracking further away from the interface occurs at lower and constant ( e *) 2 /E c representing ␥ f /a c . It is interpreted that the through-thickness variations of ( e *) 2 /E c in the ungrooved substrate specimen of the various TBCs are more largely affected by the out-of-plane compressive residual stress than ␥ f /a c .

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“…The TGO promotes the spallation of TBCs, because the TGO induces the spalling stress into the top coating near the interface to the bond coating. In contrast to numerical studies (Pindera et al, 2002;Sfar et al, 2002), there are few experimental investigations being conducted on residual stresses in TBCs ( Scardi et al, 1998;Reimmer et al, 1999).…”

Section: Introductionmentioning

confidence: 99%

Applications on High‐Energy X‐Rays to Stress Measurements of Thermal Barrier Coatings

Suzuki

Tanaka

2003

Texture, Stress, and Microstructure

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High-energy X-rays from a synchrotron radiation source, SPring-8, were applied to the stress measurements of thermal barrier coating (TBC). The specimen had a zirconia top coat on a bond coat of NiCoCrAlY sprayed on the substrate of Ni-base super alloys. The stress in the bond coat was measured through the top coat using the diffraction of Ni 3 Al 311 by high-energy X-rays with an energy of 72 keV. The sin 2 method was used to determine the stress value. A specially designed furnace with a wide beryllium window was developed to conduct in-situ measurements of the internal stress in the bond coating at the room temperature, 773, 1073, and 1373 K. The internal stress was tensile at the room temperature, and decreased with increasing temperature. At 1073 K or higher, the internal stress in the bond coat was released due to softening of the bond coat. The normal stress perpendicular to the coating surface of TBC was evaluated by a new hybrid method. Since the penetration depth of low-energy X-ray is very small around a few micrometers for zirconia, the stress value measured by the sin 2 method is the in-plane stress, 1 , and the stress perpendicular to the surface was zero. On the other hand, the penetration depth of high-energy X-rays is very deep, so the measured stress value will be the in-plane stress minus the out-of-plane stress, i.e. 1 À 3 . The normal stress perpendicular to the surface, 3 , i.e. the spalling stress, was estimated from these two measurements. The specimens were exposed in air atmosphere at 1373 K for 500, 1000, and 2000 h. The distribution of the spalling stress in the top coat was estimated by the hybrid method. The spalling stress near the interface to the bond coat changed to a large tension after long-time exposure.

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Strain gradients in plasma-sprayed zirconia thermal barrier coatings

Cited by 29 publications

References 7 publications

Residual stress determination in thermally sprayed metallic deposits by neutron diffraction

Residual stress determination in thermally sprayed metallic deposits by neutron diffraction

Through-thickness dependence of in-plane cracking behavior in plasma-sprayed thermal barrier coatings

Applications on High‐Energy X‐Rays to Stress Measurements of Thermal Barrier Coatings

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