Analysis of residual stresses in thermal barrier coatings

Teixeira, V.; Andritschky, M.; Fischer, Werner; Buchkremer, H.P.; Stöver, D.

doi:10.1016/s0924-0136(99)00157-0

Cited by 130 publications

(62 citation statements)

References 13 publications

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“…The presence of segmented cracks and interconnected porosity due to volume shrinkage and residual stresses in the top coat [2][3][4][5][6][7] affects the mechanical properties and deteriorates the oxidation and corrosion resistance. These features are considered to be the path for molten salts and corrosive gases to attack the TBC system, especially in applications where low purity fuels are burned.…”

Section: Introductionmentioning

confidence: 99%

Morphological and microstructural characterization of laser-glazed plasma-sprayed thermal barrier coatings

Batista

Portinha

Ribeiro

et al. 2006

Surface and Coatings Technology

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Laser-glazing has been revealing a high potential for the improvement of plasma-sprayed (PS) thermal barrier coatings (TBCs) by reducing surface roughness, eliminating open porosity on the surface and generating a controlled segmented crack network, although the relationship of the processing parameters with the resultant properties has not yet been completely established. In this investigation, TBCs consisting of atmospheric plasma sprayed (APS) ZrO 2 -8%wtY 2 O 3 were subjected to a CO 2 continuous wave laser glazing process in order to seal its surface porosity generating an external dense layer. For that purpose, different amounts of radiation resulting from different scanning speeds were applied to the specimens as well as different track overlapping. Results have shown a significant decrease of the surface roughness after the laser treatment. All specimens presented a fully dense and porous free external layer with a polyfaceted columnar microstructure highly adherent to the plasma-sprayed coating. Controlled surface crack networks, extremely dependent on the laser scanning speed and track overlapping, were achieved for each set of processing parameters. The cracks were found to have a tendency to be oriented in two perpendicular directions, one in the direction of the laser beam travel direction, the other perpendicular to it. Moreover, the cracks parallel to the beam moving direction are found to be on the overlapping zone, coinciding with the edge of the subsequent track. The cracks are perpendicular to the surface along the densified layer and tend to branch and deviate from the vertical direction below it, within the porous PS coating. XRD results revealed mainly t' non-transformable tetragonal zirconia with a small percentage of residual monoclinic zirconia for the as-sprayed coating. All glazed coatings presented only t' non-transformable tetragonal zirconia with some variations on preferable crystal orientation. Grain sizes varied from 26 to 52 nm, increasing with an increase of laser irradiated energy, microstrain behaved inversely. Keywords IntroductionThermal barrier coatings (TBCs) have successfully entered service in the turbine section of advanced gas turbine engines in the mid-1970s [1]. Since then, several improvements on the selected materials, processing techniques and life prediction tools have been taking place to contribute for the improvement of TBC's performance as well as for the widening of the field of applications.Current thermal barrier coating systems consist of a bond coat deposited over the material to be protected and then the TBC itself is applied to the bond coat. The metallic bond coat (MCrAlY, M=Ni, Cr or Ni/Cr) acts as a corrosion resistant layer to protect the substrate material (Nickel-based superalloy), forming alumina as the principal protective scale (thermally grown oxide (TGO)). Due to mismatch of thermoelastic properties between the metallic substrate and the ceramic top coat, the bond coat is also necessary to accommodate residual stresses avoiding its...

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Section: Introductionmentioning

confidence: 99%

Morphological and microstructural characterization of laser-glazed plasma-sprayed thermal barrier coatings

Batista

Portinha

Ribeiro

et al. 2006

Surface and Coatings Technology

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“…Of course, such large stress could not be generated in the real coating because of the strength of the sprayed top coat. Furthermore, it was reported that the residual stress in the top coat after spraying was several tens of MPa by x-ray diffraction method ( Ref 13,20,21). Then, a consideration of stress relaxation due to crack generation was necessary for analysis of the deposition process of ceramic coatings.…”

Section: Elasto-plastic Analysismentioning

confidence: 99%

A Numerical Study on Generation Mechanism of Vertical Cracks in Top Coat of TBCs During APS Deposition

2015

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Clarification of crack generation mechanism in the top coat of the thermal barrier coatings (TBCs) during atmospheric plasma spray process is important to improve the reliability of TBC. In this study, finite element analyses of stress and strain during the deposition process were conducted with layer-bylayer method to understand the cracking behaviors. Stress relaxation by generation of vertical cracks was expressed as an elasto-plastic behavior of the coating. The effects of pre-heating temperature of the substrate and plasma power on crack development were analyzed by changing of the initial and atmospheric temperatures in simulation, respectively. The simulation results of radial strain explained the experimental results of crack monitoring by non-contact laser acoustic emission method.

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“…Zirconia thin films can experience residual biaxial compressive stresses of the order of MPa to GPa, whether the material is applied as a coating (Scardi et al, 2004;Teixeira and Andritschky, 1999), or formed during thermal oxidation (Béchade et al, 2000;Jacquot et al, 1996;Petigny, 2000;P. Platt et al, 2015b;Polatidis et al, 2013;Preuss et al, 2011;Zhang et al, 2010).…”

Section: Introductionmentioning

confidence: 99%

Peridynamic simulations of the tetragonal to monoclinic phase transformation in zirconium dioxide

Platt

Mella

DeMaio

et al. 2017

Computational Materials Science

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Whether present as a manufactured stabilised ceramic, or as an oxide layer on zirconium alloys, mechanical degradation in zirconia is influenced by the tetragonal to monoclinic phase transformation.Peridynamic theory was implemented within the Abaqus finite element framework to understand how the tetragonal to monoclinic phase transformation can itself cause fracture in zirconia. In 2D these simulations represent a single grain, transforming via an isometric dilational expansion, surrounded by a homogenous monoclinic oxide. The effect of transformation time, applied bi-axial pressure, and the fracture strain were assessed using the change in strain energy and the amount of damage in the oxide surrounding the transformed grain. Reducing the applied compressive stress or applying a tensile stress reduces the transformation strain energy. The introduction of a fracture strain leads to damage in the surrounding oxide region largely in the form of cracks, and reduces the transformation strain energy further by reducing the constraint on the transforming grain. The extent of the fracture, and reduction in constraint on the transformed grain, is more significant with the application of a biaxial tensile pressure.

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Analysis of residual stresses in thermal barrier coatings

Cited by 130 publications

References 13 publications

Morphological and microstructural characterization of laser-glazed plasma-sprayed thermal barrier coatings

Morphological and microstructural characterization of laser-glazed plasma-sprayed thermal barrier coatings

A Numerical Study on Generation Mechanism of Vertical Cracks in Top Coat of TBCs During APS Deposition

Peridynamic simulations of the tetragonal to monoclinic phase transformation in zirconium dioxide

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