Erosion, corrosion and erosion–corrosion of EB PVD thermal barrier coatings

Wellman, R.G.; Nicholls, John

doi:10.1016/j.triboint.2007.10.004

Cited by 100 publications

(50 citation statements)

References 24 publications

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“…[21,25,30] 126-VOLUME 1A, JUNE 2014to destabilization of the t¢ phase. [114][115][116][117][118][119][120][121] The destabilization occurs as the zirconia is dissolved and reprecipitated in the monoclinic crystal structure. [91,116] Similarly, destabilization of the t¢ phase has been observed in the reaction of YSZ with calcium aluminosilicates, [122] artificial volcanic ash, [123] metallurgical slags, [124] and V 2 O 5 -Na 2 SO 4 .…”

Section: Corrosionmentioning

confidence: 99%

Zirconia and Pyrochlore Oxides for Thermal Barrier Coatings in Gas Turbine Engines

Fergus

2014

Metallurgical and Materials Transactions E

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One of the important applications of yttria-stabilized zirconia (YSZ) is as a thermal barrier coating for gas turbine engines. While YSZ performs well in this function, the need for increased operating temperatures to achieve higher energy conversion efficiencies, requires the development of improved materials. To meet this challenge, some rare-earth zirconates that form the cubic fluorite-derived pyrochlore structure are being developed for use in thermal barrier coatings due to their low thermal conductivity, excellent chemical stability, and other suitable properties. In this paper, the thermal conductivities of current and prospective oxides for use in thermal barrier coatings are reviewed. The factors affecting the variations and differences in the thermal conductivities and the degradation behaviors of these materials are discussed.

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Section: Corrosionmentioning

confidence: 99%

Zirconia and Pyrochlore Oxides for Thermal Barrier Coatings in Gas Turbine Engines

Fergus

2014

Metallurgical and Materials Transactions E

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“…One critical problem of the failures of TBCs is spallation or delamination of the coating layers due to mismatch of thermal expansion between the coating and the bond coat material. However, mechanical resistance such as wear or strain tolerance is the other required issue for resistance of spallation [3,[10][11][12].…”

Section: Introductionmentioning

confidence: 99%

Evaluation of Thermal Durability of Thermal Barrier Coating and Change in Mechanical Behavior

Lee¹,

Kang²,

Lee³

et al. 2017

J. Korean Ceram. Soc

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The effect of starting granules on the indentation properties of air plasma sprayed thermal barrier coatings (TBCs) is investigated in this paper. Various kinds of spray-dried granules are prepared from different processing conditions, especially varying solvent and dispersant, showing a deformed hollow-typed and a filled spherical-typed granule. The similar coating thicknesses are prepared by adjusting process parameters during air plasma spray. All XRD peaks in phase analysis are tetragonal and cubic phases without any monoclinic phase after the starting granules were heat-treated. A relatively porous microstructure of the coating layer could be obtained from the monodisperse granules, while a relatively dense microstructure resulted from the hollow-typed granules. The morphology and distribution of the granules crucially affect the microstructure of thermal barrier coatings and thus have influences on indentation properties such as indentation stress-strain curves, contact damage, and hardness. The implication concerning microstructure design of TBCs for gas turbine applications is considered.

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“…Two of the typical numerous CMAS mitigation strategies for the YSZ top coat that have been proposed in the literature entail i) the deposition of a protective coating on the surface of the top coat, or the incorporation of sacrificial materials, such as depositing a dense, non-cracked and non-porous ceramic, or metal impermeable or non-wetting outer layer to inhabit the infiltration of molten CMAS [12]; ii) the replacement of 7-8YSZ by rare-earth zirconates or low thermal conductivity rare-earth oxides [6,13]. Rare earth zirconates generally offer lower thermal conductivity and enhanced sintering resistance relative to t′-YSZ, although there are some concerns about their lower level of toughness [6,14]. However, most rare earth oxides are polymorphic at elevated temperatures and this phase transformation affects their ability to resist a thermal shock to some extent [15].…”

Section: Introductionmentioning

confidence: 99%

On the resistance of rare earth oxide-doped YSZ to high temperature volcanic ash attack

Xia

Yang

et al. 2016

Surface and Coatings Technology

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Thermal barrier coatings (TBCs), such as 7-8 wt.% yttria stabilized zirconia (YSZ), are widely used to reduce the temperature of coated materials. However, when a turbine operates in a harsh environment, for example a volcanic ash attack, sand and ash particles ingested by the engine could be deposited on the TBC surfaces as molten calcium-magnesium-alumino-silicate (CMAS). CMAS melts and penetrates into TBCs at high temperatures, which causes a loss of strain tolerance and results in the premature failure of the top coat. It is recognized that the formation of CMAS is inevitable due to exposing the turbine to sand and ash; therefore, CMAS mitigation solutions are among the top challenges for materials scientists. To some extent, CMAS is the biggest weakness of the traditional 7-8YSZ TBC material. The thermochemical interactions between YSZ and real volcanic ash are investigated in this paper as a means to alleviate the volcanic ash attack by understanding the underlying mechanisms. 7YSZ, 0.5Gd-8YSZ and 3Er-7YSZ powders and free-standing plates were prepared, respectively. The effect of the volcanic ash on the three different samples was investigated using an X-ray diffraction, scanning electron microscopy, a scanning transmission electron microscopy, and a differential scanning calorimetry. The phase transformations and reaction of TBCs materials subjected to a volcanic ash attack were examined and the volcanic ash degradation and mitigation mechanisms were discussed. It was found that rare earth-doped YSZ samples suffered less damage from the volcanic ash attack than the standard 7YSZ. The results demonstrate that rare earth-doped YSZ may be effectively utilized to mitigate a volcanic ash attack.

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Erosion, corrosion and erosion–corrosion of EB PVD thermal barrier coatings

Cited by 100 publications

References 24 publications

Zirconia and Pyrochlore Oxides for Thermal Barrier Coatings in Gas Turbine Engines

Zirconia and Pyrochlore Oxides for Thermal Barrier Coatings in Gas Turbine Engines

Evaluation of Thermal Durability of Thermal Barrier Coating and Change in Mechanical Behavior

On the resistance of rare earth oxide-doped YSZ to high temperature volcanic ash attack

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