Interaction of molten silicates with thermal barrier coatings under temperature gradients

Jackson, Richard W.; Zaleski, Elisa M.; Poerschke, David L.; Hazel, Brian; Begley, Matthew R.; Levi, Carlos G.

doi:10.1016/j.actamat.2015.01.038

Cited by 85 publications

(68 citation statements)

References 33 publications

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“…At the later stage of the experiment, the rate of progression of intrusion declines. A similar evolution of CMAS penetration depth with time was reported in isothermal conditions by Drexler et al, and was also calculated from viscous flow behaviour in gradient conditions by Jackson et al Nevertheless, both studies suggest that the pore structure is completely loaded by the CMAS melt, and the penetration rate is increasing with increasing pore radius. Considering our SEM observations of sparse infiltration, where predominantly small‐sized pores are filled and closure of coarse volumes is delayed (especially in the lower levels), the declining penetration rate may not only be attributed to the changing viscosity of the CMAS melt in the temperature gradient conditions.…”

Section: Resultssupporting

confidence: 84%

Evolution of porosity, crack density, and CMAS penetration in thermal barrier coatings subjected to burner rig testing

et al. 2019

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Degradation of thermal barrier coatings (TBCs) in gas‐turbine engines due to calcium–magnesium–aluminosilicate (CMAS) glassy deposits from various sources has been a persistent issue since many years. In this study, state of the art electron microscopy was correlated with X‐ray refraction techniques to elucidate the intrusion of CMAS into the porous structure of atmospheric plasma sprayed (APS) TBCs and the formation and growth of cracks under thermal cycling in a burner rig. Results indicate that the sparse nature of the infiltration as well as kinetics in the burner rig are majorly influenced by the wetting behavior of the CMAS. Despite the obvious attack of CMAS on grain boundaries, the interaction of yttria‐stabilized zirconia (YSZ) with intruded CMAS has no immediate impact on structure and density of internal surfaces. At a later stage the formation of horizontal cracks is observed in a wider zone of the TBC layer.

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Section: Resultssupporting

confidence: 84%

Evolution of porosity, crack density, and CMAS penetration in thermal barrier coatings subjected to burner rig testing

et al. 2019

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“…Cai et al [31] found that ZrSiO 4 forms near the top surface region of the YSZ layer and the VA penetrates the entire YSZ layer. Since the growth of ZrSiO 4 is relatively slow, blocking the inter-column gaps hardly inhibits infiltration [32]. These experimental results agree with the conclusions reached in this study.…”

Section: Discussionsupporting

confidence: 83%

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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“…YSZ TBCs degradation by CMAS attack involves two aspects, that is, thermo‐mechanical and thermo‐chemical damage . Molten CMAS penetrates into the coating and fills its pores/cracks.…”

Section: Introductionmentioning

confidence: 99%

Plasma sprayed nanostructured GdPO₄ thermal barrier coatings: Preparation microstructure and CMAS corrosion resistance

Guo

Cheng

et al. 2017

J Am Ceram Soc

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Nanostructured GdPO4 thermal barrier coatings (TBCs) were prepared by air plasma spraying, and their phase structure evolution and microstructure variation due to calcium–magnesium–alumina–silicate (CMAS) attack have been investigated. The chemical composition of the coating is close to that of the agglomerated particles used for thermal spraying. Nanozones with porous structure are embedded in the coating microstructure, with a percentage of ~30%. CMAS corrosion tests indicated that nanostructured GdPO4 coating is highly resistant to penetration by molten CMAS at 1250°C. Within 1 hour heat treatment duration, a continuous dense reaction layer forms on the coating surface, which are composed of P–Si apatite based on Ca2+xGd8−x(PO4)x(SiO4)6−xO2, anorthite and spinel phases. This layer provides effective prevention against CMAS further infiltration into the coating. Prolonged heat treatment densifies the reaction layer but does not change its phase composition.

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Interaction of molten silicates with thermal barrier coatings under temperature gradients

Cited by 85 publications

References 33 publications

Evolution of porosity, crack density, and CMAS penetration in thermal barrier coatings subjected to burner rig testing

Evolution of porosity, crack density, and CMAS penetration in thermal barrier coatings subjected to burner rig testing

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

Plasma sprayed nanostructured GdPO₄ thermal barrier coatings: Preparation microstructure and CMAS corrosion resistance

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Interaction of molten silicates with thermal barrier coatings under temperature gradients

Cited by 85 publications

References 33 publications

Evolution of porosity, crack density, and CMAS penetration in thermal barrier coatings subjected to burner rig testing

Evolution of porosity, crack density, and CMAS penetration in thermal barrier coatings subjected to burner rig testing

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

Plasma sprayed nanostructured GdPO4 thermal barrier coatings: Preparation microstructure and CMAS corrosion resistance

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Product

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Plasma sprayed nanostructured GdPO₄ thermal barrier coatings: Preparation microstructure and CMAS corrosion resistance