Artículos de revistas: "Zirconia yttria coatings"

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Anderson, A. "Determination of Abrasive Wear Resistance of Plasma Sprayed Coatings on Stainless Steel Substrate". Applied Mechanics and Materials 766-767 (junio de 2015): 579–84. http://dx.doi.org/10.4028/www.scientific.net/amm.766-767.579.

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A relative study among various types of coating materials to develop wear resistance of stainless steel has been performed. Ceramic coatings with the thickness up to 250 μm were prepared by Atmospheric plasma spray technique on the stainless steel. Two different types of coating materials such that Yttria Stabilised Zirconia, Zirconia Ceria powder were used. The influence of Ceria powder on abrasive wear was determined. It was found that the addition of Ceria to Yttria Stabilised Zirconia in a sufficient amount helped in increasing its wear resistance compared to the wear behaviour of pure Yttria Stabilised Zirconia powder. Moreover, it was found that the lesser the surface roughness of the coating layer,.

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Jech, David, Michaela Remešová, Pavel Komarov, Serhii Tkachenko, Zdeněk Česánek, Jan Schubert, Šárka Houdková y Ladislav Čelko. "Evaluation of Microstructure, Phase Composition and Hardness of Alternative Abradable Ceramic Coating Systems Produced by Means of Atmospheric Plasma Spraying". Solid State Phenomena 296 (agosto de 2019): 161–66. http://dx.doi.org/10.4028/www.scientific.net/ssp.296.161.

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Only a few types of commercially available high temperature ceramic abradable coatings are presented on the market and most of them consist of partially stabilized yttria zirconia with polymer porosity former agent and/or hBN solid lubricant. The basic demand placed on abradable coatings include balance between hardness and erosion resistance. The contribution focuses on the description of microstructure, phase composition and hardness of alternative atmospheric plasma sprayed ceramic abradable coatings deposited from four different experimental powder mixtures: (i) commercial yttria-zirconia + 5 wt. % of experimental BaF2/CaF2, (ii) commercial yttria stabilized zirconia + 10 wt. % of experimental BaF2/CaF2, (iii) R&D powder SrxTiOy and (iv) R&D powder SrxTiOy + 5 wt. % of polyester. The abradable coating systems were of ~ 150 μm thick CoNiCrAlY bond coat and of ~ 800-1000 μm thick ceramic top coat. The microstructure and phase composition of all atmospheric plasma sprayed coating systems were evaluated by the means of scanning electron microscopy and X-ray diffraction techniques. To estimate coatings basic parameters the Rockwell hardness HR15Y was measured.

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3

Shao, Hui Liang, Xin Ying Qi y Jing Jing Song. "Microstructure and Properties of Zirconia Co-Doped with Yttria and Cenosphere Coating Prepared by Air Plasma Spraying". Materials Science Forum 789 (abril de 2014): 513–17. http://dx.doi.org/10.4028/www.scientific.net/msf.789.513.

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Conventional yttria partially stabilized zirconia (YSZ) coating and zirconia co-doped with yttria and cenosphere (ZCYC) coating have been deposited by air plasma spraying (APS). Scanning electron microscope, energy spectrum analysis equipment were used to characterize the microstructure of the coatings. Pore structures made by cenosphere were found inside the ZCYC. It is noticed that adding 20% volume fraction of cenosphere in the YSZ poweders can reduce the density of the coating by 13.2%, compared with the conventional coating. The co-doping with yttria and cenophere improves the the corrosion resistance of the coating. The coating has good shock thermal and abrasion resistances with cenosphere.

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Marinenko, Ryna B., David S. Bright y Eric B. Steel. "A Study of An Yttria-Doped Zirconia Coating With Electron Microprobe Wavelength Dispersive Compositional Mapping". Microscopy and Microanalysis 3, S2 (agosto de 1997): 897–98. http://dx.doi.org/10.1017/s1431927600011375.

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Yttria-doped zirconia plasma-sprayed thermal barrier coatings (TBC’s) have been used successfully to improve the performance and extend the life of industrial equipment such as jet engines. For this reason, there is considerable interest in understanding and improving the plasma spray process and resulting TBC’s. A collaborative research program exists between Sandia National Laboratories and the National Institute of Science and Technology (NIST) to study the materials and processes used in preparing the coatings as well as the relationship between the physical properties of the coating and its microstructure.The purpose of this work was to determine the elemental compositions on a micrometer scale of an yttria-doped zirconia coating. The cubic and tetragonal crystal forms of the yttria-doped zirconia have the most favorable thermal expansion coefficient, therefore providing the most effective thermal barrier. The Y concentration in these crystal phases is known to be 6-7 wt%, while the less desirable monoclinic phase, having a less favorable thermal expansion coefficient, contains less that 3 wt% Y.

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5

Pinto, M. A., W. R. Osório, C. R. P., A. García y M. C. F. Ierardi. "Laser surface treatment of plasma-sprayed yttria-stabilized zirconia coatings". Revista de Metalurgia 41, Extra (17 de diciembre de 2005): 154–59. http://dx.doi.org/10.3989/revmetalm.2005.v41.iextra.1016.

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6

Savushkina, Svetlana, Mikhail Gerasimov, Andrey Apelfeld y Igor Suminov. "Study of Coatings Formed on Zirconium Alloy by Plasma Electrolytic Oxidation in Electrolyte with Submicron Yttria Powder Additives". Metals 11, n.º 9 (1 de septiembre de 2021): 1392. http://dx.doi.org/10.3390/met11091392.

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Coatings with thickness 40 to 150 μm were formed by plasma electrolytic oxidation (PEO) on the zirconium alloy Zr-1Nb (Zr-1% Nb) in the slurry electrolyte containing 9 g/L Na2SiO3 5H2O, 5 g/L Na(PH2O2) and 6 g/L submicron Y2O3 yttria powder during 60 min under the AC electrical mode at current densities 20; 30 and 40 A/dm2. The surface morphology, structure, composition, and corrosion-protective ability of the formed coatings have been analyzed. At PEO current density 30 A/dm2, a predominantly tetragonal phase of zirconia was formed in coatings. Increasing the PEO current density up to 40 A/dm2 promoted the formation of the coating surface layer containing submicron yttria particles. Electrochemical polarization studies in 0.5% LiOH solution showed that PEO coatings demonstrated high corrosion-protective ability. The dependence of the polarization currents on the PEO current density was found to be inconsequential.

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7

Habeeb, Mais A., Mohammed J. Kadhim, Fadhil A. Hashim y Maryam A. Bash. "Effect of Laser Treatment on the Surface Roughness of Multilayer Plasma Sprayed Thermal Barrier Coating System". Engineering and Technology Journal 39, n.º 2A (25 de febrero de 2021): 180–88. http://dx.doi.org/10.30684/etj.v39i2a.1570.

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Thermal barrier coatings (TBCs) are used in advanced engines working at higher temperatures. Higher efficiency and performance of gas turbine engines will require careful selection of TBCs. In this study, Ni22Cr10Al1.0Y (Amdry 9625) bond coat and two types of top coat including ceria stabilized zirconia (CSZ) ZrO2-24CeO2-2.5Y2O3) and yttria stabilized zirconia (YSZ) ZrO2-8Y2O3 were deposited on IN 625 by air plasma spraying (APS). The thickness of the duplex ceramic coat based on zirconia was in the range between 350 to 400 µm. The effect of high power Yb:YAG solid state laser at different laser parameters on feature, microstructure and roughness of plasma sprayed and laser sealed coating of multilayer ceria stabilized zirconia/ yttria stabilized zirconia was investigated. Surface roughness has been reduced significantly after laser sealing. The effect of laser process parameters carried out using Taguchi’s L16 orthogonal array design. Minimum roughness can be obtained at moderate power density and longer interaction time with sufficient specific energy to produce complete melting of coating. Characterization and analysis of results was achieved by employing scanning electron microscopy (SEM) , (EDS) and image J analysis. It was found from the results, there were significant improvements in the performance of plasma sprayed coatings after laser sealing due to the reduction of surface coating defects.

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Solodovnikov, Sergey, Igor Igumenov, Roman Shutilov y Vladimir Lukashov. "Functional coatings made of eco-friendly materials". E3S Web of Conferences 459 (2023): 09002. http://dx.doi.org/10.1051/e3sconf/202345909002.

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Thermal barrier coatings protect alloys (for example, in turbine blades) from extreme temperatures. There is a pressing need to find better materials than currently used yttria-stabilized zirconia (i.e. materials with better thermal stability, lower thermal conductivity, higher thermal expansion coefficient matching that of the alloy). Here we explore gehlenite (Ca2Al2SiO7) for possible application as a material for thermal barrier coatings. We found that gehlenite can indeed be used in next-generation thermal barrier coatings, as a top coat on a thin layer of yttria-stabilized zirconia.

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9

Wang, De Ren. "Alumina and Zirconia Laminar Coating Prepared by Complex Electrolytic Deposition Method". Advanced Materials Research 538-541 (junio de 2012): 391–96. http://dx.doi.org/10.4028/www.scientific.net/amr.538-541.391.

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The deposition of alumina (nano-powder, <80nm) and zirconia doped with yttria laminar composite coatings on Ni3Al coatings were investigated via a complex method of Sol-Gel, electrolytic deposition (ELD) and electrophoretic deposition (EPD). The average particle sizes of alumina and zirconia are 80nm and 20nm respectively. The relation of deposition parameters (deposition voltage, dwell time) and deposition rate was discussed based on the experiment results of alumina, zirconia single and laminated coatings deposition. The post thermal treatments were performed in attempt to acquire a dense multilayer composite ceramic coating. The uniform duplex or laminar coatings could be achieved via this complex method. The surface and cross-sectional morphologies of two layers and ten layers alumina/ zirconia composite ceramic coating after sintering showed that the laminar structure thickness could be tailored by controlling the deposition voltage and dwell time. The sintering mechanism of nano-sized alumina and zirconia was also discussed.

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10

Thibblin, Anders, Siamak Kianzad, Stefan Jonsson y Ulf Olofsson. "Running-in behaviour of thermal barrier coatings in the combustion chamber of a diesel engine". Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering 234, n.º 1 (10 de abril de 2019): 172–82. http://dx.doi.org/10.1177/0954407019841173.

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Thermal barrier coatings have the potential to improve the fuel efficiency of heavy-duty diesel engines by reducing heat losses. A method for in-situ measurement of heat flux from the combustion chamber of a heavy-duty diesel engine has been developed and was used to study the running-in behaviour of different thermal barrier coating materials and types of microstructures. The in-situ measurements show that the initial heat flux was reduced by up to 4.7% for all investigated thermal barrier coatings compared to a steel reference, except for an yttria-stabilized zirconia coating with sealed pores that had an increase of 12.0% in heat flux. Gd2Zr2O7 had the lowest initial value for heat flux. However, running-in shows the lowest values for yttria-stabilized zirconia after 2–3 h. Potential spallation problems were observed for Gd2Zr2O7 and La2Zr2O7.

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11

Salehi, Sahar y Mohammad Hosseien Fathi. "Elaboration of Sol-Gel Derived Hydroxyapatite / Yttria Stabilized Zirconia Composite Coatings Obtained for Biomedical Application". Defect and Diffusion Forum 312-315 (abril de 2011): 894–99. http://dx.doi.org/10.4028/www.scientific.net/ddf.312-315.894.

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In this study, nanostructured composite coatings of hydroxyapatite (HA)/ 30wt% yttria stabilized zirconia (YSZ) coatings containing 0, 3, 5, and 8 mol% Y2O3 (namely; HA-0YSZ, HA-3YSZ, HA-5YSZ, and HA-8YSZ) were successfully synthesized using the sol-gel method. The crystallite size of the coating was about ~44-58 nm for tetragonal and cubic zirconia grain size and 75-87 nm for hydroxyapatite grain size. Crack-free and homogeneous HA-YSZ composite coatings were obtained with no observable defects. The uniform distribution of zirconia particles in a composite would be highly beneficial for obtaining homogeneous coatings of HA-YSZ film and would hinder grain growth of HA phase during calcinations. In vitro evaluation in 0.9% NaCl showed that Ca2+ dissolution rate of composite coatings was lower than pure HA coatings.

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12

Pasupuleti Kirti Teja, Parvati Ramaswamy y Narayana Murthy S.V.S. "Thermal Shock and Oxidation Stability Tests to Grade Plasma Sprayed Functionally Gradient Thermal Barrier Coatings". Frontiers in Advanced Materials Research 1, n.º 1 (30 de mayo de 2019): 1–11. http://dx.doi.org/10.34256/famr1911.

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Functionally graded layers in thermal barrier coatings reduce the stress gradient between the overlaid ceramic coatings and the underlying metallic component. Introduced to alleviate early onset of spallation of the coating due to thermal expansion mismatch, this facilitates improvement in the life of the component. Conventional thermal barrier coatings typically comprise of duplex layers of plasma sprayed 8% yttria stabilized zirconia (ceramic) coatings on bond coated (NiCrAlY) components/substrates (Inconel 718 for example). This work highlights the superiority of plasma sprayed coatings synthesized from blends of the intermetallic bond coat and ceramic plasma spray powders on Inconel 718 substrates in three-layer configuration over the duplex layered configuration. Assessed through (a) thermal shock cyclic tests (at 1200oC and 1400oC) in laboratory scale basic burner rig test facility and (b) oxidation stability test in high temperature furnace (at 800oC and 1000oC) the functionally graded coatings of certain configurations exhibited more than double the life of the conventional 8% yttria stabilized zirconia duplex (double layer) coatings. Micro- and crystal structure analysis support the findings and results are detailed and discussed.

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13

Fu, Lei, Khiam Aik Khor y Joo Peng Lim. "Yttria stabilized zirconia reinforced hydroxyapatite coatings". Surface and Coatings Technology 127, n.º 1 (mayo de 2000): 66–75. http://dx.doi.org/10.1016/s0257-8972(00)00559-4.

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14

Kadhim, Mohammed J., Mohammed H. Hafiz y Maryam A. Ali Bash. "HARDNESS AND FRATURE TOUGHNE OF PLASMA SPRAYED ZIRCONIA-CERIA-YTTRIA THERMAL BARRIER COATINGS". IRAQI JOURNAL FOR MECHANICAL AND MATERIALS ENGINEERING 18, n.º 2 (4 de agosto de 2018): 214–28. http://dx.doi.org/10.32852/iqjfmme.vol18.iss2.87.

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Several studies have been made during the recent years to evaluate the plasma sprayedyttria partially stabilized zirconia thermal barrier coatings but less attention wereundertaken on ceria-yttria stabilized zirconia. In this study, zirconia- 20 wt% ceria-3.6wt% yttria thermal barrier coatings were produced by air plasma spraying deposited onIN 738 LC superalloy substrate. The objective of this study is to analysis the distributionof porosity, hardness and fracture toughness on the deposited coatings. Under optimumplasma spraying conditions, it is dangerous to consider the mean values of hardness andfracture toughness. The distributions of hardness and fracture toughness are highlyscattered. The Weibull distribution is the main parameter to describe the plasma sprayedcoatings hardness and fracture toughness.

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15

Kokini, Klod y Sudarshan V. Rangaraj. "Time-Dependent Behavior and Fracture of Functionally Graded Thermal Barrier Coatings under Thermal Shock". Materials Science Forum 492-493 (agosto de 2005): 379–84. http://dx.doi.org/10.4028/www.scientific.net/msf.492-493.379.

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The thermal fracture and its dependence on time-dependent behavior in functionally graded yttria stabilized zirconia - NiCoCrAlY bond coat alloy thermal barrier coatings was studied. The response of three coating architectures of similar thermal resistance to laser thermal shock tests was considered, experimentally and computationally.

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16

Zou, Lanxin, Minghao Gao, Na Xu, Jia Zhang y Xinchun Chang. "CMAS Corrosion Behavior of Nanostructured YSZ and Gd-Yb-Y-Stabilized Zirconia Coatings". Coatings 13, n.º 9 (15 de septiembre de 2023): 1623. http://dx.doi.org/10.3390/coatings13091623.

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With the development of industry, the operating temperature of aero engines and gas turbines continues to increase; developing thermal barrier coatings (TBCs) with superior resistance to CaO-MgO-Al2O3-SiO2 (CMAS) corrosion has become a prominent research focus. In this study, atmospheric plasma spraying (APS) was used to prepare yttria-stabilized zirconia (YSZ), nanostructured yttria-stabilized zirconia (n-YSZ), and Gd-Yb-Y-stabilized zirconia (GYYSZ) coatings. The effects of CMAS exposure on the microstructure, chemical composition, phase transition, and microhardness of the coatings were investigated. Comparative analysis revealed that both phase transition and exfoliation occurred in corroded YSZ and n-YSZ coatings, with n-YSZ exhibiting more pronounced changes. In contrast, GYYSZ coatings remained stable without phase transition and exhibited a smaller increase in microhardness (270 HV0.3). Consequently, doping Gd/Yb/Y elements into ZrO2 can improve the performance of TBCs.

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Scardi, Paolo, Matteo Leoni, M. Loch y G. Barbezat. "Elastic Behaviour of Thin Stabilized-Zirconia Coatings". Materials Science Forum 443-444 (enero de 2004): 77–82. http://dx.doi.org/10.4028/www.scientific.net/msf.443-444.77.

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The residual stress in thin coatings of yttria stabilised-zirconia produced by Low Pressure Plasma Spraying were measured by X-ray Diffraction, using laboratory as well as synchrotron radiation sources. The specific microstructure, with absence of texture and fine distribution of nearly equiaxed grains, point out that despite the markedly anisotropic nature of cubic zirconia, coatings can be considered as macroscopically isotropic. This picture is also confirmed by the results of a parallel study, where the X-ray elastic constants were measured in-situ along two crystallographic directions ([440] and [620]): measured values agree fairly well with those calculated from single-crystal data under the Neerfeld-Hill assumptions. SR XRD provided a detailed information on the stress field across the thickness of the zirconia coatings. In particular the presence of a stress gradient was observed and modelled. The average stress is compressive, and increases with the coating thickness. Compression tend to increase from the surface toward the inside of the coating reaching a maximum of ~-1.0 GPa in a 24 µm coating.

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Rudolphi, Mario, Mathias Christian Galetz y Michael Schütze. "Mechanical Stability Diagrams for Thermal Barrier Coating Systems". Journal of Thermal Spray Technology 30, n.º 3 (febrero de 2021): 694–707. http://dx.doi.org/10.1007/s11666-021-01163-5.

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AbstractLoss of mechanical integrity due to thermal aging and subsequent spallation of the ceramic top layer is one of the dominant failure mechanisms in thermal barrier coating systems. In order to predict and avoid such mechanical failure, a strain-based lifetime assessment model is presented for a novel double-layer thermal barrier system. The investigated ceramic system consists of a gadolinium zirconate layer on top of a layer of yttria-stabilized zirconia prepared by atmospheric plasma spraying. The mechanical stability diagrams generated by the model delineate areas of safe operation from areas where mechanical damage of the thermal barrier coating becomes imminent. Intensive ceramographic inspection is used to investigate the defect growth kinetics in the ceramic top coat after isothermal exposure. Four-point bending experiments with in situ acoustic emission measurement are utilized to determine the critical strain to failure. The results are then used to generate mechanical stability diagrams for the thermal barrier coatings. From these diagrams, it becomes evident that the gadolinium zirconate layer has significantly lower strain tolerance than the yttria-stabilized zirconia. However, the underlying yttria-stabilized zirconia layer will provide some thermal protection even when the gadolinium zirconate layer has failed.

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19

Qureshi, Imran Nazir, Muhammad Shahid y A. Nusair Khan. "Effect of Na₂SO₄-V₂O₅ Mixture on Y₂O₃ Stabilized ZrO₂ Thermal Barrier Coatings Exposed at High Temperature". Advanced Materials Research 1101 (abril de 2015): 423–27. http://dx.doi.org/10.4028/www.scientific.net/amr.1101.423.

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Yttria stabilized zirconia thermal barrier coating (TBC) along with CoNiCrAlY bondcoat was deposited using air plasma spray on Inconel-X750 superalloy. The coated samples were exposed at 9500C in a mixture of Na2SO4and V2O5. The exposed specimens were investigated using XRD and SEM. The formation of spinel and perovskite structures was revealed at the interface of topcoat and the bondcoat. XRD analyses of the samples confirmed phase transformation of the tetragonal zirconia into monoclinic zirconia and yttrium vanadate.

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Anzabi, O., M. M. Aydin, L. S. Ozyegin, F. N. Oktar, Kārlis A. Gross, Gültekin Göller, E. S. Kayali y E. Z. Erkmen. "Characterization of Plasma Sprayed Yittria Stabilized Zirconia (8 wt %) Hydroxyapatite Coatings". Key Engineering Materials 493-494 (octubre de 2011): 535–38. http://dx.doi.org/10.4028/www.scientific.net/kem.493-494.535.

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Splitting problems at HA-coated implants are generally due to biological reasons. Bond-coatings were used to prevent the splitting problem of zirconia ceramics; this method can be widely seen in industrial applications. Two main groups were used; the first group consisted of spraying a bond layer of titania onto commercially pure titanium. This followed by a spray of HA with 5, 10 and 15 % zirconia (8 % yttria doped) as main layer onto the first bond-coating. For the second group, the samples were coated without bond-coating. Firstly, X-ray diffraction patterns of the starting powders were taken. Then x-ray diffraction patterns of the plasma sprayed samples were taken. In literature, it was seen that 20 % zirconia was sufficient for the transformation into a monoclinic structure for the bond-coated samples. For this study it was found that 10 % zirconia was sufficient to transform to the same structure of the desired crystalline phase transformation. The coating kept its crystal structure and relatively small amount of amorphous transformation was detected. A similar structure was produced using less zirconia. It was thought that the use of titanium-oxide bond-coating layer would play an important role as a third variable in the results. To further investigate these phenomena, more detailed researches must be conducted with using titanium-oxide yittria stabilized zirconia (8 wt %) hydroxyapatite bond-coatings with HA main coatings.

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Cano, Francisco J., Orlando Castilleja-Escobedo, L. J. Espinoza-Pérez, Cecilia Reynosa-Martínez y Eddie Lopez-Honorato. "Effect of Deposition Conditions on Phase Content and Mechanical Properties of Yttria-Stabilized Zirconia Thin Films Deposited by Sol-Gel/Dip-Coating". Journal of Nanomaterials 2021 (13 de octubre de 2021): 1–9. http://dx.doi.org/10.1155/2021/4449890.

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The effect of yttria concentration (0-33.4 mol%), extraction rates (0.17, 0.33, 0.50, and 0.67 mm s-1), and the number of layers (up to four) on the phase content, surface defects, thickness, hardness, adhesion strength, and wear rate of yttria-stabilized zirconia coatings produced by sol-gel/dip-coating were studied for its use on thermolabile substrates. At 700°C, a metastable tetragonal phase ( t ″ ) was obtained even with 33.4 mol% yttria when heat treated for 24 hours; however, a fully cubic structure was attained by extending the heat treatment up to 48 hours as confirmed by Raman spectroscopy. Furthermore, it was necessary to use withdrawal speeds of at least 0.67 mm s-1 to produce defect-free coatings. Although the coatings were produced at low temperature, they showed 41% lower wear rate than steel and an adhesion strength of 30 MPa. Our work stresses the importance of the heat treatment history on the stabilization of the cubic phase in sol-gel YSZ coatings.

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Fu, Lei, Khiam Aik Khor y Joo Peng Lim. "Effects of Yttria-Stabilized Zirconia on Plasma-Sprayed Hydroxyapatite/Yttria-Stabilized Zirconia Composite Coatings". Journal of the American Ceramic Society 85, n.º 4 (20 de diciembre de 2004): 800–806. http://dx.doi.org/10.1111/j.1151-2916.2002.tb00175.x.

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23

Alpe´rine, S. y L. Lelait. "Microstructural Investigations of Plasma-Sprayed Yttria Partially Stabilized Zirconia TBC (In Relation to Thermomechanical Resistance and High-Temperature Oxidation Mechanisms)". Journal of Engineering for Gas Turbines and Power 116, n.º 1 (1 de enero de 1994): 258–65. http://dx.doi.org/10.1115/1.2906802.

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This study deals with microstructural investigations of plasma-sprayed yttria partially stabilized zirconia thermal barrier coatings, performed by classical and analytical transmission electron microscopy. The aim of the study was to determine eventual relationships between coating microstructure and toughness. The ceramic/metal interface, which plays an important role during TBC thermomechanical solicitation, has also been studied. In the 6–8 wt. percent Y2O3 range, the metastable tetragonal t′ phase is observed, showing special faulted microstructural features, such as grain twinning and antiphase boundary planes. Moreover, after high-temperature annealing in air, a very fine and stable precipitation of the equilibrium cubic phase appears. It is believed that these microstructural elements could act as crack deviation sites and enhance the coatings’ intrinsic toughness. Microstructural investigations of the alumina scales grown during high-temperature annealing reveal yttrium segregation at oxide grain boundaries as well as significant quantities of zirconium inside the alumina grains. The oxide growth seems to be dominated by a classical grain boundary oxygen diffusion mechanism. The presence of zirconium inside the alumina grains suggests that Al2O3 also partially forms by chemical reduction of ZrO2 by Al.

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Susnitzky, D. W. "Vanadia-induced transformations in yttria-stabilized zirconia". Proceedings, annual meeting, Electron Microscopy Society of America 46 (1988): 792–93. http://dx.doi.org/10.1017/s0424820100106028.

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Thermal-barrier coatings for jet-engine components are typically composed of Y2O3-stabilized ZrO2 (YSZ) since this material provides improved ceramic-to-metal bonding, thermal-stress resistance and stability. One problem associated with YSZ thermal barriers is the increased rate of coating failures encountered when trace amounts of impurities, such as 50ppm vanadium, are present in the jet fuel. V2O5 reacts with YSZ to form YVO4 and a monoclinic ZrO2 phase. Although coating failures are attributed to the 3-5% volume change associated with the tetragonal- to-monoclinic transformation, the exact mechanism of V2O5 attack has been unclear. The present study addresses the deleterious effects of V2O5 on YSZ at 810°-950°C by directly exposing perforated TEM specimens of single-crystal YSZ to the vapor produced by a small quantity of V2O5 powder. The experimental details of this thin-film reaction technique have been described elsewhere.Fig.l shows a bright-field (BF) image recorded from a (100)-oriented YSZ (9mol% Y2O3) specimen which was exposed to V2O5 vapor for 30 min at 810°C.

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VALLEJO, N. DIAZ, O. SANCHEZ, J. C. CAICEDO, W. APERADOR y G. ZAMBRANO. "HOT CORROSION OF YTTRIUM STABILIZED ZIRCONIA COATINGS DEPOSITED BY AIR PLASMA SPRAY ON A NICKEL-BASED SUPERALLOY". Surface Review and Letters 24, n.º 06 (24 de noviembre de 2016): 1750084. http://dx.doi.org/10.1142/s0218625x17500846.

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In this research, the electrochemical impedance spectroscopy (EIS) and Tafel analysis were utilized to study the hot corrosion performance at 700[Formula: see text]C of air plasma-sprayed (APS) yttria-stabilized zirconia (YSZ) coatings with a NiCrAlY bond coat grown by high velocity oxygen fuel spraying (HVOF), deposited on an INCONEL 625 substrate, in contact with corrosive solids salts as vanadium pentoxide V2O5 and sodium sulfate Na2SO4. The EIS data were interpreted based on proposed equivalent electrical circuits using a suitable fitting procedure performed with Echem AnalystTM Software. Phase transformations and microstructural development were examined using X-ray diffraction (XRD), with Rietveld refinement for quantitative phase analysis, scanning electron microscopy (SEM) was used to determinate the coating morphology and corrosion products. The XRD analysis indicated that the reaction between sodium vanadate (NaVO[Formula: see text] and yttrium oxide (Y2O[Formula: see text] produces yttrium vanadate (YVO[Formula: see text] and leads to the transformation from tetragonal to monoclinic zirconia phase.

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Szabó, Ádám I., Álmos D. Tóth, Máté Zs Leskó y Hajnalka Hargitai. "Investigation of the Applicability of Y2O3–ZrO2 Spherical Nanoparticles as Tribological Lubricant Additives". Lubricants 10, n.º 7 (12 de julio de 2022): 152. http://dx.doi.org/10.3390/lubricants10070152.

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Long-term environmental goals will motivate the automotive industry, component suppliers, and lubricating oil developers to reduce the friction of their tribosystems to improve overall efficiency and wear for increased component lifetime. Nanoscale ceramic particles have been shown to form a protective layer on components’ surface that reduces wear rate with its high hardness and chemical resistance. One such ceramic is yttria (Y2O3), which has an excellent anti-wear effect, but due to its rarity it would be extremely expensive to produce engine lubricant made from it. Therefore, part of the yttria is replaced by zirconia (ZrO2) with similar physical properties. The study presents the result of the experimental tribological investigation of nanosized yttria–zirconia ceramic mixture as an engine lubricant additive. Yttria-stabilized zirconia (YSZ) nanoparticle was used as the basis for the ratio of the ceramic mixture, so that the weight ratio of yttria–zirconia in the resulting mixture was determined to be 11:69. After the evaluation of the ball-on-disc tribological measurements, it can be stated that the optimal concentration was 0.4 wt%, which reduced the wear diameter by 30% and the wear volume by 90% at the same coefficient of friction. High-resolution SEM analysis showed a significant amount of zirconia on the surface, but no yttria was found.

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Zhou, Hong, Jun Wang, Bo He, Fei Li, Jing Ma y Bao De Sun. "Mechanical Properties of Nanostructured Zirconia Coatings Fabricated by Air Plasma Spraying". Key Engineering Materials 368-372 (febrero de 2008): 1280–83. http://dx.doi.org/10.4028/www.scientific.net/kem.368-372.1280.

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Nanostructured coatings are experiencing a rapid development in recent years due to their potential applications in a wide variety of technological areas. In order to improve the properties of thermal barrier coatings, nanostructured 8 wt% yttria partial stabilized zirconia coatings were deposited by air plasma spraying with reconstituted nanoparticles on titanium alloy substrates. For comparison, the conventional counterparts were also fabricated. Their microstructures were investigated by using transmission electron micrograph and scanning electron micrograph. Their mechanical behaviors were evaluated via Vickers microhardness test and tensile test. The results indicate that the nanostructured zirconia coatings with original nanostructure and columnar grains have higher microhardness and adhesive strength than the conventional counterparts. Both the nanostructured coating and the conventional coating exhibit a bimodal distribution of microhardness values, which are analyzed via Weibull statistics. This phenomenon is attributed to the presence of molten and non-molten parts in the coatings.

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28

Wan, Chun Lei, Wei Pan, Zhi Xue Qu y Ye Xia Qin. "Thermophysical Properties of Samarium-Cerium Oxide for Thermal Barrier Coatings Application". Key Engineering Materials 336-338 (abril de 2007): 1773–75. http://dx.doi.org/10.4028/www.scientific.net/kem.336-338.1773.

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Sm0.4Ce0.6O1.8 specimen with a defective fluorite structure was synthesized and its thermophysical properties were characterized for thermal barrier coatings (TBCs) application. At high temperature, Sm0.4Ce0.6O1.8 exhibited much lower thermal conductivity than 7wt% yttria-stabilized zirconia (7YSZ)-the commonly used composition in current TBCs. Sm0.4Ce0.6O1.8 also possessed large thermal expansion coefficient, which could help reduce the thermal mismatch between the ceramic coating and bond coat.

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Manogaran, Rajasekaramoorthy, Karthikeyan Alagu, Anderson Arul, Anandh Jesuraj, Dinesh Kumar Devarajan, Govindhasamy Murugadoss y Kamalan Kirubaharan Amirtharaj Mosas. "Hot Corrosion Behavior of Plasma-Sprayed Gd2Zr2O7/YSZ Functionally Graded Thermal Barrier Coatings". Ceramics 7, n.º 2 (29 de abril de 2024): 579–95. http://dx.doi.org/10.3390/ceramics7020038.

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The development of advanced thermal barrier coating (TBC) materials with better hot corrosion resistance, phase stability, and residual stresses is an emerging research area in the aerospace industry. In the present study, four kinds of TBCs, namely, single-layer yttria-stabilized zirconia (YSZ), single-layer gadolinium zirconate (GZ), bilayer gadolinium zirconate/yttria-stabilized zirconia (YSZ/GZ), and a multilayer functionally graded coating (FGC) of YSZ and GZ, were deposited on NiCrAlY bond-coated nickel-based superalloy (Inconel 718) substrates using the atmospheric plasma spray technique. The hot corrosion behavior of the coatings was tested by applying a mixture of Na2SO4 and V2O5 onto the surface of TBC, followed by isothermal heat treatment at 1273 K for 50 h. The characterization of the corroded samples was performed by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS) to identify physical and chemical changes in the coatings. GIXRD was used to analyze the residual stresses of the coatings. Residual stress in the FGC coating was found to be −15.2 ± 10.6 MPa. The wear resistance of TBCs is studied using a linear reciprocating tribometer, and the results indicate that gadolinium zirconate-based TBCs showed better performance when deposited in bilayer and multilayered functionally graded TBC systems. The wear rate of as-coated FGC coatings was determined to be 2.90 × 10−4 mm3/Nm, which is lower than the conventional YSZ coating.

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Reis, Danieli A. P., Carlos de Moura Neto, Antônio Augusto Couto, Cosme Roberto Moreira Silva, Francisco Piorino Neto y M. J. R. Barboza. "A Comparison between CoNiCrAlY Bond Coat and Zirconia Plasma Sprayed Coatings on Creep Tests". Materials Science Forum 591-593 (agosto de 2008): 30–35. http://dx.doi.org/10.4028/www.scientific.net/msf.591-593.30.

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Thermomechanical and electrical properties of zirconia-based ceramics have led to a wide range of advanced and engineering ceramic applications like solid electrolyte in oxygen sensors, fuel cells and furnace elements and its low thermal conductivity has allowed its use for thermal barrier coatings for aerospace engine components. A comparison between CoNiCrAlY bond coat and zirconia plasma sprayed coatings on creep tests of the Ti-6Al-4V alloy was studied. The material used was commercial Ti-6Al-4V alloy. Yttria (8 wt.%) stabilized zirconia (YSZ) with a CoNiCrAlY bond coat was atmospherically plasma sprayed on Ti-6Al-4V substrates by Sulzer Metco Type 9 MB. Constant load creep tests were conducted on a standard creep machine in air on coated samples, at stress levels of 520 MPa at 500°C to evaluate the oxidation protection on creep of the Ti-6Al-4V alloy. Results indicate that the creep resistance of the ceramic coating was greater than metallic coating.

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31

Zhang, Wenfei, Bin Hua, Mengmeng Miao, Ken Cadien y Jing-Li Luo. "High ionic conductivity of ultralow yttria concentration yttria-stabilized zirconia thin films". Journal of Vacuum Science & Technology A 40, n.º 4 (julio de 2022): 042405. http://dx.doi.org/10.1116/6.0001736.

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This paper investigates the ionic conductivity of ultralow yttria concentration (<2 mol. %) yttria-stabilized-zirconia (YSZ) thin films synthesized by atomic layer deposition (ALD). With our ALD recipe, yttria is homogeneously distributed among zirconia, and its concentration is controlled by the pulse time of the yttrium precursor. High conductivity values are observed at test temperatures (400, 500, and 600 °C). 1.6YSZ exhibits a conductivity of 0.02 S cm−1 at 600 °C and an activation energy of 0.98 eV. In order to relate the electrical property, atomic force microscope and x-ray diffraction are used to study the crystallinity and microstructure. The true size effect is considered to be responsible for the outstanding electrical property. Finally, the effects of YSZ thin film thickness and annealing process on their conductivities are studied. The true size effect is weakened by an increase in grain size from annealing or higher thickness, leading to reduced ionic conductivities.

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32

Drajewicz, Marcin, Kamil Dychtoń y Marek Góral. "Thermal Properties of YSZ Powders for Plasma Spraying". Solid State Phenomena 227 (enero de 2015): 413–16. http://dx.doi.org/10.4028/www.scientific.net/ssp.227.413.

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The oxides in the case of theirs properties are important materials for industrial application especially, in aircraft industry for application as thermal barrier coatings. Thermal properties of zirconium oxide stabilized by yttria are better than other ceramic materials. This powder could be stabilized in room temperature by addition of rare earth elements. In this article the thermal analyses of yttria stabilized zirconia (YSZ) oxide are presented as a baseline for future measurements of thermal properties of YSZ powder with addition of rare earth elements. The thermal expansion, specific heat, thermal diffusivity and thermal conductivity of commercially available Matco 6700 powder offered by Sulzer Metco company were analyzed by thermal methods.

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McCrabb, Heather, Joseph Kell y Binod Kumar. "Pulse Electric Fields for EPD of Thermal Barrier Coatings". Key Engineering Materials 507 (marzo de 2012): 21–25. http://dx.doi.org/10.4028/www.scientific.net/kem.507.21.

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Conventional electrophoretic deposition is being combined with pulse electric fields to deposit yttria stabilized zirconia from ethanol based suspensions onto bondcoated turbine alloys for thermal barrier coatings. The addition of the pulse electric fields to the electrophoretic process has demonstrated the capability to decrease the coating roughness, minimize hydrolysis, and decrease coating edge effects commonly encountered in electrokinetic and electrochemical deposition processes. Subsequent to the electrophoretic deposition process the green body coatings were subjected to a combined binder burnout and sintering process for further coating densification. The coatings have been qualified in terms of surface roughness as well as microstructure and experiments have been performed to show that the pulse EPD process can deposit TBC materials onto turbine components.

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Rezaee, S., Gh R. Rashed y M. A. Golozar. "Electrochemical and Oxidation Behavior of Yttria Stabilized Zirconia Coating on Zircaloy-4 Synthesized via Sol-Gel Process". International Journal of Corrosion 2013 (2013): 1–9. http://dx.doi.org/10.1155/2013/453835.

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Sol-gel 8 wt.% Yttria Stabilized Zirconia (YSZ) thin films were prepared on zirconium (zircaloy-4 alloy) by dip-coating technique followed by heat treating at various temperatures (200°C, 400°C, and 700°C) in order to improve both electrochemical corrosion and high temperature oxidation properties of the substrate. Differential thermal analysis and thermogravimetric analysis (DTA-TG) revealed the coating formation process. X-ray diffraction (XRD) was used to determine the crystalline phase structure transformation. The morphological characterization of the coatings was carried out using scanning electron microscopy (SEM). The electrochemical behavior of the coated and uncoated samples was investigated by means of open circuit potential, Tafel, and electrochemical impedance spectroscopy (EIS) in a 3.5 wt.% NaCl solution. The homogeneity and surface appearance of coatings produced was affected by the heat treatment temperature. According to the corrosion parameters, the YSZ coatings showed a considerable increase in the corrosion resistance, especially at higher heat treatment temperatures. The coating with the best quality, from the surface and corrosion point of view, was subjected to oxidation test in air at 800°C. The coated sample presented a 25% reduction in oxidation rate in comparison with bare substrate.

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35

Ali Bash, Maryam A., Sami A. Ajeel, Ruqayah A. Abbas y Mohammed J. Kadhim. "A Direct Laser Sintering Approach for the Electrophoretic Deposition Overlay of Yttria-Stabilized Zirconia on the Surface of a Thermal Barrier Coating System". Coatings 13, n.º 10 (27 de septiembre de 2023): 1695. http://dx.doi.org/10.3390/coatings13101695.

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The laser sintering process and modification of yttria-stabilized zirconia (YSZ) coatings subjected to electrophoretic deposition (EPD) on YSZ air-plasma-sprayed (APS) thermal barrier coatings (TBCs) were investigated. A Ni-based superalloy was plasma-sprayed using yttria-stabilized zirconia (YSZ) to create a thermal barrier coating with a 400 μm thickness. The electrophoretic deposition (EPD) technique was used to deposit the nanopowder of YSZ on the surface of YSZ TBCs. In this study, a technology based on the direct sintering of a green EPD layer using a laser beam was employed. The best conditions for the deposition overlay of the YSZ coating using a DC current were obtained with an applied voltage of 40 V, deposition time of 5 min, and suspension concentration of 10 g/L. Iodine was added to the solutions as a stabilizing agent. To overcome the problems of high sintering temperatures, laser sintering was adopted as a new approach. The microstructures of all the specimens were studied using field emission scanning electron microscopy (FESEM) with energy-dispersive X-ray spectroscopy (EDS) analysis. Surface roughness was investigated using atomic force microscopy (AFM) analysis and the central line average (CLA). The direct laser sintering (DLS) process for the EPD overlay on the surface of the TBCs caused a reduction in surface roughness and porosity, and improvements in the microstructural and mechanical properties of the surface coatings were observed.

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Smialek, James y Robert Miller. "Revisiting the Birth of 7YSZ Thermal Barrier Coatings: Stephan Stecura †". Coatings 8, n.º 7 (22 de julio de 2018): 255. http://dx.doi.org/10.3390/coatings8070255.

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Thermal barrier coatings are widely used in all turbine engines, typically using a 7 wt.% Y2O3–ZrO2 formulation. Extensive research and development over many decades have refined the processing and structure of these coatings for increased durability and reliability. New compositions demonstrate some unique advantages and are gaining in application. However, the “7YSZ” (7 wt.% yttria stabilized zirconia) formulation predominates and is still in widespread use. This special composition has been universally found to produce nanoscale precipitates of metastable t’ tetragonal phase, giving rise to a unique toughening mechanism via ferro-elastic switching under stress. This note recalls the original study that identified superior properties of 6–8 wt.% yttria stabilized zirconia (YSZ) plasma sprayed thermal barrier coatings, published in 1978. The impact of this discovery, arguably, continues in some form to this day. At one point, 7YSZ thermal barrier coatings were used in every new aircraft and ground power turbine engine produced worldwide. 7YSZ is a tribute to its inventor, Dr. Stephan Stecura, NASA retiree.

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Shapiro, Ian P., Xiao Feng Zhao, Hui Xu y Ping Xiao. "Monitoring Constrained Sintering of YSZ Coatings Using Fluorescence Spectroscopy and Micro-Hardness". Key Engineering Materials 412 (junio de 2009): 177–82. http://dx.doi.org/10.4028/www.scientific.net/kem.412.177.

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The constrained sintering behavior of yttria stabilized zirconia coatings containing 1 wt. % alumina produced using electrophoretic deposition has been studied. Coatings have been characterized by scanning electron microscopy, micro-hardness and fluorescence spectroscopy after sintering in air at 1100°C and 1200°C. These coatings were compared with those that additionally contained 1 wt. % soda-lime glass. Micro-hardness and fluorescence spectroscopy are shown to accurately monitor the density of the coatings. Fluorescence spectroscopy showed that the density across the coating is even, as expected from modelling literature. The addition of 1 wt. % of soda-lime glass is shown to improve the sintered density of coatings.

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Marple, Basil R., Joël Voyer, Michel Thibodeau, Douglas R. Nagy y Robert Vassen. "Hot Corrosion of Lanthanum Zirconate and Partially Stabilized Zirconia Thermal Barrier Coatings". Journal of Engineering for Gas Turbines and Power 128, n.º 1 (30 de julio de 2004): 144–52. http://dx.doi.org/10.1115/1.1924534.

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The hot corrosion resistance of lanthanum zirconate and 8wt.% yttria-stabilized zirconia coatings produced by thermal spraying for use as thermal barriers on industrial gas turbines or in aerospace applications was evaluated. The two ceramic oxide coatings were exposed for various periods of time at temperatures up to 1000°C to vanadium- and sulfur-containing compounds, species often produced during the combustion of typical fuels used in these applications. Changes in the coatings were studied using a scanning electron microscope to observe the microstructure and x-ray diffraction techniques to analyze the phase composition. The results showed different behaviors for the two materials: the zirconia-based coating being rapidly degraded by the vanadium compounds and resistant to attack by the sulfur materials while the lanthanum zirconate was less damaged by exposure to vanadia but severely attacked in the presence of sulfur-containing species.

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39

Jones, Robert L., Richard F. Reidy y Derek Mess. "Scandia, yttria-stabilized zirconia for thermal barrier coatings". Surface and Coatings Technology 82, n.º 1-2 (julio de 1996): 70–76. http://dx.doi.org/10.1016/0257-8972(95)02646-0.

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CHEN, L. B. "YTTRIA-STABILIZED ZIRCONIA THERMAL BARRIER COATINGS — A REVIEW". Surface Review and Letters 13, n.º 05 (octubre de 2006): 535–44. http://dx.doi.org/10.1142/s0218625x06008670.

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Thermal barrier coatings (TBCs), which protect metallic components from high-temperature environments, have been widely applied to the fields of high-temperature and corrosion-resistant structural parts such as gas turbine engines, diesel engines, and power generation systems. Yttria-stabilized zirconia (YSZ) is one of the most widely used materials for TBCs owing to its excellent shock resistance, low-thermal conductivity, and relatively high coefficient of thermal expansion. In this paper the properties of YSZ and the recent developments of YSZ-TBCs are reviewed. The failure mechanism of YSZ-TBCs and corresponding methods for lengthening the lifetime of YSZ-TBCs are discussed. The advantages of graded thermal barrier coatings and the problems in processing are elucidated.

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41

Yaghtin, Amirhossein, Maryam Yaghtin, Pooria Najafisayar, Zhaolin Tang y Tom Troczynski. "On the Applicability of Modified Water-Based Yttria-Stabilized Zirconia Suspensions to Produce Plasma-Sprayed Columnar Coatings". Coatings 13, n.º 8 (28 de julio de 2023): 1330. http://dx.doi.org/10.3390/coatings13081330.

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In this paper, the applicability of the modified water-based yttria-stabilized zirconia (YSZ) suspensions, including different dispersants, to produce plasma-sprayed coatings with a “columnar microstructure” is investigated. The effects of processing parameters, like the suspension liquid-phase ethanol content, change in substrate roughness, and spray distance on the resulting coating morphologies, are investigated. The results showed that increasing the ethanol concentration, substrate surface roughness, and spray distance promotes the formation of coatings with a columnar structure. Moreover, the application of modified water-based suspensions, including the α-Terpineol dispersant, has led to the deposition of columnar coatings with comparable morphologies of coatings deposited from ethanol-based suspensions.

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42

Zhang, Panpan, Xiaofeng Zhang, Fuhai Li, Zhihui Zhang, Hong Li, Yueliang Wang, Luquan Ren y Min Liu. "Effects of Selective Laser Modification and Al Deposition on the Hot Corrosion Resistance of Ceria and Yttria-Stabilized Zirconia Thermal Barrier Coatings". Coatings 9, n.º 6 (30 de mayo de 2019): 353. http://dx.doi.org/10.3390/coatings9060353.

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The air-plasma-sprayed ceria and yttria-stabilized zirconia (CYSZ) coating was modified by selective laser remelting and Al deposition to enhance hot corrosion resistance. The dotted coating was obtained after selective laser remelting. Magnetron sputtering was used to deposit an Al film on the dotted coating, and a vacuum heat treatment was subsequently performed to produce a dense α-Al2O3 overlay. Hot corrosion behavior of the following three types of coatings was investigated: plasma-sprayed, dotted, and dotted coatings combined with Al deposition (DA). Hot corrosion behaviors were evaluated in a mixture of 55 wt % V2O5 and 45 wt % Na2SO4 molten salts at 1000 °C for 30 h. The hot corrosion reaction between molten salts and zirconia stabilizers (Y2O3 and CeO2) led to the generation of monoclinic zirconia, YVO4, and CeVO4 plate-shaped crystals, and the mineralization of CeO2. The results indicated that the hot corrosion resistance of the DA coating was the best, and the dotted coating had superior hot corrosion resistance in comparison with the plasma-sprayed coating. The minimal surface roughness and dense dotted units improved the hot corrosion resistance of the dotted coating. The dense α-Al2O3 overlay with chemical inertness effectively inhibited the infiltration of molten salts, which led to the optimal hot corrosion resistance of the DA coating.

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43

Pan, Wei, Qiang Xu, Long Hao Qi, Jing Dong Wang, He Zhuo Miao, Kazutaka Mori y Taiji Torigoe. "Novel Low Thermal Conductivity Ceramic Materials for Thermal Barrier Coatings". Key Engineering Materials 280-283 (febrero de 2007): 1497–500. http://dx.doi.org/10.4028/www.scientific.net/kem.280-283.1497.

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The increase of the efficiency for gas turbines leads to the increasing combustion-chambertemperatures. Rapid degradation of the conventional yttria-stabilized zirconia coatings does not fulfill therequirements at these temperatures for a reliable thermal barrier coatings (TBCs) due to the phasetransformation of zirconia and the sintering behaviour. Therefore, it is very important to develop novelceramic materials for TBCs with low thermal conductivity and long-term stability at high temperatures.In this paper, the developments of potential novel ceramic materials for TBCs with low thermalconductivity are reviewed.

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Fenech, Justine, Céline Viazzi, Florence Ansart y Jean Pierre Bonino. "Elaboration of Sol-Gel Coatings from Aerogels and Xerogels of Doped Zirconia for TBC Applications". Advanced Materials Research 89-91 (enero de 2010): 184–89. http://dx.doi.org/10.4028/www.scientific.net/amr.89-91.184.

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Thermal Barrier Coatings (TBCs) are used as insulators on hot section components to reduce operating temperatures in aircraft engines and industrial gas turbine. The TBC system consists of two layers: the ceramic top coat traditionally Yttria Stabilized Zirconia (YSZ) with a low conductivity, and the bond coat generally MCrAlY, M=Ni and/or Cr or Co or Pd or Pt modified aluminides. In the industry, two dry-route processes used to deposit TBCs give quite different microstructures of coatings. In one hand, coatings resulted by plasma spraying (PS) present a lamellar microstruture with a low thermal conductivity in the range from 0.7 to 0.9 Wm−1K−1. In the other hand, Electron Beam Physical Vapour Deposition (EBPVD) coatings with columnar microstruture coatings present the best mechanical performances but perpendicular orientation of the columns makes their thermal conductivity twice higher compared to PS coatings. The present study proposes the elaboration of zirconia coatings via the sol-gel route combined with dip-coating process. It is a versatile process able to produce either thin ceramic coatings or thick deposits. The main advantage of this method is to decrease the crystallization temperature, much lower than conventional processes. Moreover, the sol-gel process is a nondirectional deposition technique, which is very different to the physical methods described above. Doped zirconia have been chosen to constitute isolating multilayers coatings. Sol formulation, slurries stability but also dip-coating conditions have been optimized in order to obtain homogeneous layers on nickel based superalloys substrates.

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Lützke, Friedrich, Markus Maier, Aleksandra Urbanska, Rolf Zehbe, Claudia Fleck, Wolf Dieter Müller y Carolina Mochales. "Electrophoretic Deposition of Zirconia Multilayered Constructs". Key Engineering Materials 631 (noviembre de 2014): 13–17. http://dx.doi.org/10.4028/www.scientific.net/kem.631.13.

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Zirconia-based ceramics have gained considerable interest for several applications (e.g. solid electrolytes in fuel cells and in oxygen sensors, thermal barrier coatings and biomaterials for dental and orthopaedic applications) due to their high mechanical strength, improved fracture toughness and easy affordability. We constructed both a manual and an automated electrophoretic deposition set-ups, which allowed us to obtain multilayers of alternating tetragonal and cubic phases by layering nanometric sized powders of yttria doped zirconia (Y-TZP) with different mol percentages of yttria (3 % and 8 %). The rationale behind the design of these multilayer constructs was to optimize the properties of the final ceramic by combining the high mechanical toughness of the tetragonal phase of zirconia together with the high ionic conductivity of its cubic phase. These multilayered constructs were proved to have good mechanical integrity and a clearly defined interface between the cubic zirconia grains layer and the tetragonal zirconia grains layer.

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46

Ahmadi Pidani, Raheleh, Reza Shoja Razavi, Reza Mozafarinia y Hossein Jamali. "Comparison of Hot Corrosion Resistance of YSZ and CYSZ Thermal Barrier Coatings in Presence of Sulfate-Vanadate Molten Salts". Advanced Materials Research 472-475 (febrero de 2012): 141–44. http://dx.doi.org/10.4028/www.scientific.net/amr.472-475.141.

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In this study, NiCoCrAlY bond coat and two types of top coat including yttria stabilized zirconia (YSZ) and ceria and yttria stabilized zirconia (CYSZ) were deposited on IN 738LC by air plasma spraying (APS). Hot corrosion behavior of samples in 1000 °C was study using 55wt.%V2O5-45wt.%Na2SO4 corrosive salt. Characterization and analysis of results was done by employing field emission scanning electron microscope (FESEM) and x-ray diffractometry (XRD). Results ravealed that plasma sprayed CYSZ TBCs exhibited excellent hot corrosion resistance which was superior to that of YSZ TBCs due to strong acidity and high contents of stabilizer.

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Reza, Mohammad S., Syarifah N. Aqida, Mohd Radzi Mohd Toff y Dermot Brabazon. "Thermal Barrier Coatings on Laser Surface Modified AISI H13 Tool Steel Using Atmospheric Plasma Spray Technique". Key Engineering Materials 554-557 (junio de 2013): 603–10. http://dx.doi.org/10.4028/www.scientific.net/kem.554-557.603.

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This paper presents yttria-stabilized zirconia (YSZ) coating deposition on laser surface modified H13 tool steel using atmospheric plasma spray (APS) technique. A Praxair Plasma Spray System with SG-100 gun was used to deposit coating materials on laser-modified H13 tool steel substrate surface. A bond coat layer material was NiCrAlY alloy while the top coat was yttria stabilized zirconia (YSZ) with powder size distribution range of-106 μm to +45 μm. A 23design of experiment (DOE) was used to deposit bond coat and top coat powders with three controlled factors of input current, powder feed rate and stand-off-distance. The design was optimised for minimum porosity and maximum hardness. The coating thickness and percentage of porosity were measured using IM7000 inverted optical microscope. Hardness properties of top coating layer were measured by using MMT-X7 Matsuzawa Hardness Tester Machine with Vickers hardness scale. The microscopy findings indicated variations of coating thickness at different parameters settings. Samples at the highest current and powder feed rate and lowest stand-off distance settings produced a lower porosity percentage and higher hardness. A higher powder feed rate with the smallest stand-off-distance allowed melted powders to travel uniformly onto the substrate surface. These findings were significant to development of thermal barrier coatings on semi-solid forming die surface.

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Aravind, Anoop y G. R. Kannan. "Experimental Studies of Mechanical and Microstructure Properties of Plasma Sprayed Thermal Barrier Coatings". Applied Mechanics and Materials 592-594 (julio de 2014): 326–32. http://dx.doi.org/10.4028/www.scientific.net/amm.592-594.326.

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This research work mainly deals with the mechanical and microstructure properties of various thermal barrier coating (TBC) materials for an internal combustion engine piston using plasma spraying technique. Three thermal barrier coating Materials namely the combination of Aluminium Oxide with Titanium oxide (87%Al2O3 + 13%Tio2), Aluminium Oxide with Titanium oxide (97% Al2O3 +3%Tio2) and Yttria Stabilized Zirconia (YSZ) (100%) were selected and coated on Aluminium Alloy(Al Ai) with the thickness of 150 Microns (µm) for this investigation. Among three Thermal barrier coating materials, Yttria Stabilized Zirconia showed better mechanical properties such as elongation (EL) of 6.25%, tensile strength TS of 106.06MPa and yield strength (YS) of 90.34MPa when compared with that of the base piston metal Aluminium Alloy (Al Ai). Further, better microstructure properties were also observed for YSZ (100%) in comparison with other thermal barrier coated materials.

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Lauwagie, T., K. Lambrinou, Iulian Mircea, Marion Bartsch, W. Heylen y Omer Van der Biest. "Determining the Elastic Moduli of the Individual Component Layers of Cylindrical Thermal Barrier Coatings by Means of a Mixed Numerical - Experimental Technique". Materials Science Forum 492-493 (agosto de 2005): 653–58. http://dx.doi.org/10.4028/www.scientific.net/msf.492-493.653.

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Cylindrical specimens made of the Ni-based super-alloy Inconel 625 (IN 625) were coated with (a) NiCoCrAlY, or (b) NiCoCrAlY and yttria-stabilised zirconia (YSZ: in this case, zirconia with 7-8 wt% yttria), using the electron beam - physical vapor deposition (EB-PVD) technique. In the bi-layer coatings, the YSZ layer is the thermal barrier coating (TBC) and the NiCoCrAlY layer is the metallic bond coat (BC). The BC improves the bonding between the substrate and the ceramic TBC, while the low thermal conductivity of the TBC oers high-temperature protection to the substrate. This paper focuses on the determination of the elastic moduli of the substrate and the coating layers of the test samples. The elastic moduli of the three dierent materials (IN 625, NiCoCrAlY and YSZ) were determined by means of a mixed numerical - experimental technique (MNET). The employed MNET was based on the comparison of the experimentally measured resonant frequencies of the rst bending mode of the test samples to the numerically calculated ones. The unknown elastic properties were determined by ne-tuning the elastic material parameters of the numerical models so as to enable the reproduction of the experimentally measured resonant frequencies.

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Caio, Fernanda y Christian Moreau. "Influence of Substrate Shape and Roughness on Coating Microstructure in Suspension Plasma Spray". Coatings 9, n.º 11 (11 de noviembre de 2019): 746. http://dx.doi.org/10.3390/coatings9110746.

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This study investigated the influence of the substrate shape and roughness on the microstructure of suspension plasma spray (SPS) coatings. For this purpose, an yttria-stabilized zirconia (YSZ) suspension was sprayed on flat and curved stainless-steel substrates by SPS. The suspension was composed of 20 wt.% YSZ particles in ethanol. After spraying, the morphology of the coatings was characterized by scanning electron microscopy (SEM). The results showed that the substrate shape influences the amount of coating material deposited and microstructural features of the coating. The amount of coating material deposited was seen to decrease as the radius of curvature decreased. Finally, the roughness was found to influence the formation of columnar structure.

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