Interaction and infiltration behavior of Eyjafjallajökull, Sakurajima volcanic ashes and a synthetic CMAS containing FeO with/in EB-PVD ZrO 2 -65 wt% Y 2 O 3 coating at high temperature

Naraparaju, Ravisankar; Chavez, Juan J. Gomez; Schulz, Uwe; Ramana, C. V.

doi:10.1016/j.actamat.2017.06.055

Cited by 66 publications

(54 citation statements)

References 36 publications

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“…Infiltration time is expected to be higher for this type of long feather model. Similar behavior was also observed in the experiments comparing coarse and feathery structures of the top coat columns [19,24] As the contact surface areas between the CMAS flow path and the top coat boundaries retard the flow rate due to frictional effects, for an increased contact surface area slow infiltration was obtained.…”

Section: Influence Of Feather Length (Gap) On Total Infiltration Behasupporting

confidence: 80%

“…The CMAS infiltration kinetics was studied experimentally in previous researches [19,24] for the case of coarse and feathery morphologies (see Figure 2b,c). The overall porosity (gaps between columns and feathers) in the feathery structure was almost 2.5 times higher than that of the coarse structure.…”

Section: Qualitative Comparison With Experimental Infiltration Behaviormentioning

confidence: 99%

“…In past years, considerable attempts were made on the improvement of TBC systems aiming at reducing the infiltration and contamination by molten silicates [14][15][16][17][18][19]. Several methodologies were suggested to enforce the mitigation mechanisms against CMAS, which fall under two broad categories.…”

Section: Introductionmentioning

confidence: 99%

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Flow Kinetics of Molten Silicates through Thermal Barrier Coating: A Numerical Study

et al. 2019

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Infiltration of molten calcium–magnesium–alumina–silicates (CMAS) through thermal barrier coatings (TBCs) causes structural degradation of TBC layers. The infiltration kinetics can be altered by careful tailoring of the electron beam physical vapor deposition (EB-PVD) microstructure such as feather arm lengths and inter-columnar gaps, etc. Morphology of the feathery columns and their inherent porosities directly influences the infiltration kinetics of molten CMAS. To understand the influence of columnar morphology on the kinetics of the CAMS flow, a finite element based parametric model was developed for describing a variety of EB-PVD top coat microstructures. A detailed numerical study was performed considering fluid-solid interactions (FSI) between the CMAS and TBC top coat (TC). The CMAS flow characteristics through these microstructures were assessed quantitatively and qualitatively. Finally, correlations between the morphological parameters and CMAS flow kinetics were established. It was shown that the rate of longitudinal and lateral infiltration could be minimized by reducing the gap between columns and increasing the length of the feather arms. The results also show that the microstructures with long feather arms having a lower lateral inclination decrease the CMAS infiltration rate, therefore, reduce the CMAS infiltration depth. The analyses allow the identification of key morphological features that are important for mitigating the CMAS infiltration.

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Section: Influence Of Feather Length (Gap) On Total Infiltration Behasupporting

confidence: 80%

Section: Qualitative Comparison With Experimental Infiltration Behaviormentioning

confidence: 99%

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Flow Kinetics of Molten Silicates through Thermal Barrier Coating: A Numerical Study

et al. 2019

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“…The formation of garnet is arguably promoted by the presence of Fe in the deposit, as inferred from its absence in reactions of YMS with the equivalent Fe-free deposit (C 33 M 9 A 13 S 45 ), which yield only apatite. 17 This inference is further supported by previous reports of garnet formation from Fe-containing deposits 29 but not from Fe-free deposits. 15 Encapsulation of apatite crystals by garnet further suggests that garnet begins to form at a later stage of the reaction.…”

Section: F I G U R Esupporting

confidence: 75%

Reactions of molten silicate deposits with yttrium monosilicate

et al. 2020

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The article addresses effects of silicate deposit composition on reactions with yttrium monosilicate (YMS), a candidate environmental barrier coating for aero-engine components. Computed phase equilibria are used to predict the nature and relative proportions of reaction products and the extent of YMS consumption upon reaction with twelve deposits of varying composition at 1300°C. These predictions are compared with results of a corresponding experimental study on three exemplary deposits.Although the nature and sequence of reaction products formed (typically apatite and yttrium disilicate) depend on the Ca:Si ratio of the deposit, the degree of consumption of YMS at equilibrium is relatively insensitive to deposit composition and is predicted to proceed to a greater extent than that in yttrium disilicate. However, sluggish reaction kinetics associated with the formation of a thin apatite layer above the YMS prevents reactions from reaching their terminal equilibrium states within the experimental times investigated (250 hours). For deposit loadings of 18 mg/cm 2 (corresponding to a thickness of about 100 µm), the degree of consumption following 250 hours exposures is only about 10%-40% of the predicted terminal values, depending on deposit composition. K E Y W O R D Schemical reactions, CMAS, Environmental barrier coating, yttrium silicate 2920 | SUMMERS Et al.

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“…There are many reports about CMAS degradation of YSZ coatings. Both APS [17][18][19][20][21] and EB-PVD [22][23][24] coatings were investigated and some studies on the effect of CMAS were based on ex-service vanes and blades. 25,26 The envisaged damage mechanism can be divided into two effects 27,28 : thermo-mechanical effect and thermo-chemical reaction.…”

Section: Introductionmentioning

confidence: 99%

Failure of plasma sprayed nano‐zirconia‐based thermal barrier coatings exposed to molten CaO–MgO–Al₂O₃–SiO₂ deposits

et al. 2019

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Recently, nanostructured thermal barrier coatings have received considerable attention because of some superior properties in comparison with their conventional counterpart. In this study, nanostructured 8 wt% yttria‐stabilized zirconia (n‐YSZ) coatings were deposited by atmospheric plasma spraying, and the degradation behavior caused by molten calcium‐magnesium‐aluminon‐silicate (CMAS) attack was investigated. Results showed that the thermo‐chemical reaction product between CMAS and YSZ (both powders and coatings) is different with the change of CMAS content. At low CMAS concentration, a cubic phase is generated by the diffusion of Ca into YSZ grains. As compared to the conventional YSZ, less C‐ZrO2 is detected for n‐YSZ. When CMAS reaches a certain concentration (eg 15 mg/cm2), disruptive phase transformation from tetragonal to monoclinic will occur and the reaction is more readily for n‐YSZ. Two different chemical reaction mechanisms governing the CMAS content effect were proposed. It should be noted that the nanozone in the coatings plays an important role in the CMAS degradation process, which enhances CMAS infiltration rate and accelerates the chemical reaction, leading to a poor CMAS resistance of the nanostructured coating than that of the conventional counterpart.

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Interaction and infiltration behavior of Eyjafjallajökull, Sakurajima volcanic ashes and a synthetic CMAS containing FeO with/in EB-PVD ZrO 2 -65 wt% Y 2 O 3 coating at high temperature

Cited by 66 publications

References 36 publications

Flow Kinetics of Molten Silicates through Thermal Barrier Coating: A Numerical Study

Flow Kinetics of Molten Silicates through Thermal Barrier Coating: A Numerical Study

Reactions of molten silicate deposits with yttrium monosilicate

Failure of plasma sprayed nano‐zirconia‐based thermal barrier coatings exposed to molten CaO–MgO–Al₂O₃–SiO₂ deposits

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Interaction and infiltration behavior of Eyjafjallajökull, Sakurajima volcanic ashes and a synthetic CMAS containing FeO with/in EB-PVD ZrO 2 -65 wt% Y 2 O 3 coating at high temperature

Cited by 66 publications

References 36 publications

Flow Kinetics of Molten Silicates through Thermal Barrier Coating: A Numerical Study

Flow Kinetics of Molten Silicates through Thermal Barrier Coating: A Numerical Study

Reactions of molten silicate deposits with yttrium monosilicate

Failure of plasma sprayed nano‐zirconia‐based thermal barrier coatings exposed to molten CaO–MgO–Al2O3–SiO2 deposits

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Product

Resources

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Failure of plasma sprayed nano‐zirconia‐based thermal barrier coatings exposed to molten CaO–MgO–Al₂O₃–SiO₂ deposits