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Tsui, Yun Cheong. "Adhesion of plasma sprayed coatings." Thesis, University of Cambridge, 1996. https://www.repository.cam.ac.uk/handle/1810/283710.
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Ru, Tao. "Spray Parameters Influence on Suspension Plasma Sprayed Zirconia coatings properties." Thesis, Högskolan Väst, Avd för tillverkningsprocesser, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:hv:diva-6960.
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Thermal barrier coatings (TBCs) are a simple and proven method to protect hot section components. Suspension Plasma Spray (SPS), an emerging process technology to generate TBCs, compared with traditional Atmospheric Plasma Spray APS, can deposit thinner coat-ings with finer microstructure. Operating parameters play an important role in developing certain properties of coating. In this thesis work, power level, gas flow rate, number of spray-ing strokes, spray gun's nozzle size i.e. internal diameter and suspension rate were controlled to produce coatings with different microstructures and porosity levels. According to the ex-perimental results, the power level of plasma gun play an essential role on coating micro-structure, for instance, the density of vertical cracks increased with growing the power level. The number of spraying strokes showed also an impact on coating porosity. However, due to different nozzle sizes i.e. diameter, the same coating property were controlled by different operating parameters. For coatings deposited by small and large nozzles, their coating thick-ness and roughness mainly relied on power level and gas flow rate. In contrary, it seems that the coating roughness was not influenced by the same parameters when it was deposited by medium nozzle. Also, gas flow rate do not have as big as influence on coating thickness
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Gill, Stephen Charles. "Residual stresses in plasma sprayed deposits." Thesis, University of Cambridge, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.386108.
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Fox, A. C. "Gas permeation through plasma sprayed ceramic coatings." Thesis, University of Cambridge, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.599155.
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This work has addressed the gas transport rate and mechanism through plasma sprayed coatings. This is of particular interest for thermal barrier coatings (TBCs) and solid oxide fuel cell electrodes. Deposits of ZrO2 - 8 wt% Y2O3, ZrO2 - 14 wt% Y2O3 and A12O3 have been plasma sprayed under varying conditions. Microstructural studies and density measurements have been carried out to characterise the porosity content and microcrack distribution. Crystallographic phase analysis and Young's Modulus measurements have also carried out. The gas permeability of each specimen has been measured at temperatures up to 600°C. These measurements involve a thin disc of the coating being sealed over a ceramic tube. A mass flow controller was used to set a constant gas flow rate, and the resulting pressure difference across the coating was measured once steady state had been reached. D'Arcy's Law was then used to determine the specific permeability of each specimen. Measurements were carried out on the coatings using hydrogen, oxygen and nitrogen as the permeating gases. Values of the specific permeability were of the order of 10-16m2 for zirconia coatings and 10-17 m2 for alumina coatings. These results were correlated with microstructural observations via a simple analytical model for gas permeation, based on Percolation Theory. In this model, large pores were treated as isolated cavities with connecting microcracks, predicting a high sensitivity to the density and connectivity of microcracks. Good agreement was obtained between theory and experiment in terms of the magnitude of the permeability. The oxygen flux through the top coat of a TBC has been calculated from the permeability of the coating. Published values of the diffusion coefficient have been used to calculate the oxygen flux by diffusion. These 2 transport mechanisms have been compared and gas permeation has been found to dominate over diffusion at the operating temperatures of a TBC. Oxide growth at the bond coat / top coat interface of a TBC has been shown to be controlled by diffusion through the oxide layer.
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Cipitria, Amaia. "Sintering of plasma-sprayed thermal barrier coatings." Thesis, University of Cambridge, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.612066.
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Sokolowski, Pawel. "Properties of suspension plasma sprayed zirconia coatings using different plasma torches." Thesis, Limoges, 2016. http://www.theses.fr/2016LIMO0133/document.
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Dans cette thèse plusieurs questions scientifiques concernant la projection plasma de suspensions (SPS) revêtements de zircone ont été étudiées. Les revêtements ont été analysées principalement en termes de l'application comme isolant top-coat des revêtements de barrière thermique (TBC). Ces revêtements multicouches sont appliqués sur les parties métalliques par exemple, Les turbines à gaz pour les protéger contre les charges thermiques élevées provoquées par les gaz d'échappement chauds. Mais l'évaluation initiale de la possibilité de l'utilisation de la projection plasma de suspensions pour produire la couche d'électrolyte en pile à combustible à oxyde solide (SOFC) a été fait aussi. SOFC semblent être les types de piles à combustible les plus prometteurs actuellement. (Voir le chapitre 1-2 de la revue de la littérature).Le premier objectif de recherche important était d'analyser la possibilité de produire des revêtements étant différents en termes de la microstructure. L'objectif principal était d'obtenir des revêtements caractérisés par une structure très poreuse et irrégulière (appelé colonnaires-like), mais aussi des revêtements très denses et homogènes avec typique, deux zones microstructure. A cet effet, les deux poudres de zircone ont été utilisées: (i) l'oxyde de zirconium entièrement stabilisé à l'yttria et (ii) de la zircone yttria-oxyde de cérium stabilisé. Les poudres ont des compositions chimiques différentes, la taille des particules et leur morphologie. Ces poudres ont été utilisées pour une formulation de suspension. L'autre variable dans le procédé de pulvérisation est la concentration de la suspension. La suspension avec une teneur en matières solides dans la gamme de 2,5 et 30 en poids % ont été préparées et projetée. Toutes les suspensions ont été produites au laboratoire. Un concept très important de ce travail est l'utilisation de quatre différents, disponibles dans le commerce, des torches à plasma, à savoir: (i) SG-100, (ii) TriplexPro-200, (iii) Axial III et (iv) WSP-H 500. Les torches étaient différentes en termes de conception, l'énergie électrique, le modede stabilisation du plasma et l'angle d'injection de suspension. En raison des grandes différences entre les torches à plasma et SPS set-ups les paramètres du procédé de pulvérisation ont été choisis dans chaque cas individuellement. La dernière variable dans la conception de l'expérience était la topographie et la rugosité du substrat afin d'évaluer son influence sur les revêtements des mécanismes de croissance-up. Les substrats ont été préparés avant la projection par: (i) le grenaillage, (ii) le traitement au laser et par (iii) le broyage. L'expérience de projection large a permis une analyse complexe de SPS revêtements microstructure, des mécanismes de croissance des revêtements et le développement de processus SPS lui-même. [...]In this PhD thesis several scientific issues regarding Suspension Plasma Sprayed (SPS) zirconia coatings were studied. The coatings were analyzed mainly in terms of the application as insulating top-coat of Thermal Barrier Coatings (TBC’s). These multilayer coatings are applied onto the metallic parts of e.g. gas turbines to protect them against high temperature loads caused by the hot exhaust gases. But the initial assessment of the possibility of the use of Suspension Plasma Spraying to produce electrolyte layer in Solid Oxide Fuel Cells was done also. SOFC’s seem to be the most promising fuel cell types currently. (See Chapter 1-2 with the literature review) The first important research goal was to analyze the possibility of producing coatings being various in terms of the microstructure. The main aim was to obtain coatings characterized by very porous and irregular structure (called columnar-like) but also very dense and homogeneous coatings with typical two-zones microstructure. For this purpose two zirconia powders were used: (i) fully yttria-stabilized zirconia and (ii) ytrria-ceria-stabilized zirconia. The powders had different chemical composition, particle size and morphology. These powders were used for a suspension formulation. The other variable in the spray process was suspension concentration. The suspension with a solid content in range of 2.5 and 30 wt. % were prepared and sprayed. All suspensions were home-produced. A very important concept of this work was the use of four various, commercially-available, plasma torches, namely: (i) SG-100, (ii) TriplexPro-200, (iii) Axial III and (iv) WSP-H 500. The torches were different interms of design, electric power, plasma stabilization mode and the suspension injection angle. Due to the big differences between plasma torches and SPS set-ups the spray process parameters were chosen in each case individually. The last variable in theexperiment design was the topography and roughness of substrate in order to evaluate its influence on the coatings growth-up mechanisms. The substrates were prepared prior to spraying by: (i) grit-blasting, (ii) laser-treatment and by (iii) grinding. The wideii spray experiment allowed complex analysis of SPS coatings microstructure, coatings growth-up mechanisms and the development of SPS process itself. [...]
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Fazan, Fazilah. "In vitro behaviour of plasma sprayed hydroxyapatite coatings." Thesis, University of Birmingham, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.369349.
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Thompson, Joseph Andrew. "Thermomechanical behaviour of plasma-sprayed thermal barrier coatings." Thesis, University of Cambridge, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.621757.
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Tsipas, Sofia Alexandra. "Thermophysical properties of plasma sprayed thermal barrier coatings." Thesis, University of Cambridge, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.615144.
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Westergård, Richard. "Enhancement of the Tribological Properties of Plasma Sprayed Alumina." Doctoral thesis, Uppsala universitet, Institutionen för materialvetenskap, 2002. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-2076.
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Thermal spraying is the name of a large group of coating deposition techniques used to deposit thick layers for a variety of applications. The principle is to melt the material, and rapidly propel the droplets towards a substrate where they flatten and solidify. When properly used, the substrate is not significantly heated. Spraying enables deposition of practically any material with a stable molten phase, on any solid material. Sprayed ceramics are used to reduce wear by sliding and by hard particles. However, due to the defect-filled microstructure resulting from spraying, the coatings typically have poor mechanical and tribological properties compared to dense, sintered materials. By varying the spraying parameters, the microstructure of the coatings was influenced, and also the wear rate and cohesion, which is difficult to quantify. Improved tribological properties resulted from spraying with axial particle injection equipment and using narrowly size distributed, spherically shaped powder particles, compared to conventional equipment and powder particles. A new method to seal the open pores of sprayed ceramic coatings by electrolysis is proposed and evaluated. It was found that almost complete sealing could be obtained, in some cases giving a drastically improved wear behaviour. The studied electrolytically deposited sealants were Pb, Sn, Cu and Ni. The latter was found to give the best performance. It also proved possible to apply PVD coatings to the sprayed ceramics, and it was shown that sprayed and Ni-sealed alumina can be superior to ball bearing steel to support thin, low friction PVD coatings.
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Erickson, Lynn C. "Wear and microstructural integrity of ceramic plasma sprayed coatings." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0008/NQ38881.pdf.
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Kingswell, Russ. "Properties of vacuum plasma sprayed alumina and tungsten coatings." Thesis, Brunel University, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.303346.
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Moghisi, M. "Ultrasonic and acoustic emission studies of plasma sprayed coatings." Thesis, University of Bath, 1985. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.332455.
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This work assesses the potentials of two NDE techniques namely ultrasonic C-scan and acoustic emission for evaluating plasma sprayed coating quality. The coating materials used were aluminium (Metco 54), alumina (Metco 105), molybdenum (Mob3) and self-fusing molybdenum (Mo5O5). It has been established that ultrasonic C-scan imaging can reliably detect thickness variations of the order of 0.05mm in plasma sprayed coatings. Also, by using this technique it is possible to detect the presence of delamination or lack of adhesion between the coating and substrate. Although it was only possible to produce aluminium and alumina coatings with artificially introduced adhesion defects, it has been shown that the presence of such defects in other coatings can also be detected. It has been established that an ultrasonic C-scan technique is not sensitive to the process parameters of plasma spraying. The process parameters investigated were; poor surface preparation, input power and surface cooling. Another major limitation of ultrasonic C-scan technique is the geometrical restrictions where components with high curvatures can not be tested. Acoustic emission activities from plasma sprayed coatings were monitored during four point bend testing. Samples sprayed on poorly prepared surfaces or sprayed without coolant air could be distinguished from control samples using AE characteristics at low strain levels. Also the AE response of the alumina coatings reflected the thickness of the coatings. Thicker coatings produced more AE events. The AE response of the molybdenum (Mo63) and self-fusing molybdenum (Mo5O5) coatings were complex. It was found that they were related to the residual stresses in the coatings. Aluminium coatings showed very little acoustic emission activities.
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Jasim, Mohammed. "Failure analysis of suspension plasma sprayed thermal barrier coatings." Thesis, Högskolan Väst, Forskningsmiljön produktionsteknik(PTW), 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:hv:diva-12142.
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Thermal barrier coatings (TBC) are proven to protect the hot section of components operated under elevated temperature. Suspension Plasma Spray (SPS) is an emerging manufacturing process that is used to produce TBCsI, It has the ability to deposit a thinner TBC that has finer microstructure than coatings deposited using traditional Atmospheric Plasma Spray (APS). The coating spray parameters have a significant role in developing the coating properties and thereby the coatings failure. In this thesis work, the parameters such as the spray distance, the feed rate, and the surface velocity were varied to deposit six sets of TBC samples. The as-sprayed samples were analysed and next tested at different temperatures (1000°C, 1050°C and 1100°C) making thermal cyclic fatigue test (TCF) and thermal shock test also known as Burner Rig Test (BRT). These investigations aimed at trying to find an explanation for the effect of each varied process parameter on the deposited TBC. However the cases at 1100°C were not reliable enough to conclude. It was found that most porous coating was produced in Run 1. The porosity decreased gradually from Run 1 to the last run (Run 6) by changing the spray parameters. The failure in all cases was mainly due to the Thermally Grown Oxide (TGO) which causes cracking near the topcoat-bond coat interface. According to many cross sectional and top surface morphology SEM images taken during this work, the sintering of TBCs during thermal cycling also played a significant role in the top coat failure.
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Howard, Simon James. "The interfacial toughness of plasma sprayed coatings on titanium alloys." Thesis, University of Cambridge, 1993. https://www.repository.cam.ac.uk/handle/1810/283686.
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Uczak, de Goes Wellington. "Suspension plasma sprayed thermal barrier coatings for internal combustion engines." Licentiate thesis, Högskolan Väst, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT), 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:hv:diva-15198.
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The upward trend in internal combustion engine efficiency is likely driven by the depletion of fossil fuels. Since no replacement in sight can deliver energy comparable to the conventional oil, there is a need to use it more rationally and effectively. Thermal barrier coatings have been seen for a long time as a solutionto increase the thermal efficiency of gas turbine engines but suffer from the lackof strong applicability in internal combustion engines. This is due to the different restrictions when comparing the environment on the gas turbines and in internal combustion engines. To overcome this problem and, at the same time, expand the application field of thermal barrier coatings, more efforts need to be devoted.In this work, different top coat materials using various deposition techniques were evaluated and categorized in three different thermal barrier coating (TBC) architectures. The first was the lamellar yttria-stabilized zirconia (YSZ) top coat deposited by atmospheric plasma spray (APS), used as a reference sample. The second architecture was a columnar suspension plasma spray (SPS) TBC with YSZ and gadolinium zirconate (GZO) top coat. The SPS process can produce avariety of microstructures, and they were, for the first time, tested in an internal combustion engine. The third architecture was an SPS top coat, with an additional layer on the top, called a sealing layer of either metallic or ceramic material, both never investigated in a diesel engine application earlier. For the thermophysical properties investigation, a combination of laser flashanalysis (LFA) and modeling with object-oriented finite element (OOF) was employed to understand the properties in all the applications. The performance of the coatings was evaluated in two different ways, by thermal cyclic tests, basedon the TBCs behavior under cyclic thermal loads and by single-cylinder engine experiment. The characterization of the coatings was done by scanning electron microscope (SEM) before and after the thermal cyclic tests.The performance properties were correlated with coatings microstructure and thermophysical properties. It was shown that a columnar TBC produced by SPS had a superior engine efficiency in the single cylinder engine experiment.
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Zhang, Xing Xing. "The erosion of plasma-sprayed alumina coatings by solid particle impact." Thesis, University of Cambridge, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.386758.
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Wolfe, Kristy L. "Evaluation of plasma sprayed coatings as surface pretreatments for adhesive bonding." Thesis, This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-06162009-063427/.
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Tantra, Nauzad. "Selective emoval of plasma-sprayed thermal barrier coatings (TBC's) using pure waterjets." Thesis, University of Nottingham, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.537683.
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Seraffon, Maud. "Performances of air plasma sprayed thermal barrier coatings for industrial gas turbines." Thesis, Cranfield University, 2012. http://dspace.lib.cranfield.ac.uk/handle/1826/7772.
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Future industrial gas turbines will be required to operate at higher temperatures to increase operating efficiencies and will be subjected to more frequent thermal cycles. The temperatures that the substrates of components exposed in the harshest environments experience can be reduced using air-cooling systems coupled with ceramic thermal barrier coatings (TBCs); however, few studies have been carried out at the substrate temperatures encountered in industrial gas turbines (e.g. 900 – 1000 °C). Better understanding of their behaviour during service and, their various potential failure mechanisms, would allow more accurate prediction of TBC lifetimes and improve coatings. The aim of this research, as a part of the Supergen Plant Life Extension (PLE) project, was (a) to investigate the influence of industrial gas turbine blade geometry on TBC system lifetimes, and (b) to extend knowledge on the effect of bond coat composition on the oxide growth at temperatures below 1000 °C. The main results of this thesis, obtained using mass change and characterisation techniques, increase the understanding of the significant interactions between the different coating layers, samples’ geometry, interdiffusion and failure mechanisms involved during oxidation. Curvature was found to affect the quality of manufacture and thus promoted premature failure at the convex features of modified aerofoil-shaped samples. In parallel new bond coat compositions, suitable for industrial gas turbines were suggested from the wide range investigated in oxidation exposures. The selective growth of protective Cr2O3 or Al2O3 oxides or other mixed oxides was observed and mapped in ternary diagrams. Furthermore two novel techniques were successfully used during this project. Pulsed flash thermography proved to be efficient in identifying areas of sub-surface TBC delamination non-destructively. Magnetron co-sputtering using 2 and 3 targets was found to be a flexible method to deposit thick coatings with a wide range of compositions.
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Ganvir, Ashish. "Microstructure and Thermal Conductivity of Liquid Feedstock Plasma Sprayed Thermal Barrier Coatings." Licentiate thesis, Högskolan Väst, Avd för tillverkningsprocesser, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:hv:diva-9061.
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Thermal barrier coating (TBC) systems are widely used on gas turbine components to provide thermal insulation and oxidation protection. TBCs, incombination with advanced cooling, can enable the gas turbine to operate at significantly higher temperatures even above the melting temperature of the metallic materials. There is a permanent need mainly of environmental reasons to increase the combustion turbine temperature, hence new TBC solutions are needed.By using a liquid feedstock in thermal spraying, new types of TBCs can be produced. Suspension plasma/flame or solution precursor plasma spraying are examples of techniques that can be utilized for liquid feedstock thermal spraying.This approach of using suspension and solution feedstock, which is an alternative to the conventional solid powder feed stock spraying, is gaining increasing research interest, since it has been shown to be capable of producing coatings with superior coating performance.The objective of this research work was to explore relationships between process parameters, coating microstructure, thermal diffusivity and thermal conductivity in liquid feedstock thermal sprayed TBCs. A further aim was to utilize this knowledge to produce a TBC with lower thermal diffusivity and lower thermal conductivity compared to state-of-the-art in industry today, i.e. solid feed stock plasma spraying. Different spraying techniques, suspension high velocity oxy fuel,solution precursor plasma and suspension plasma spraying (with axial and radialfeeding) were explored and compared with solid feedstock plasma spraying.A variety of microstructures, such as highly porous, vertically cracked and columnar, were obtained. It was shown that there are strong relationships between the microstructures and the thermal properties of the coatings.Specifically axial suspension plasma spraying was shown as a very promising technique to produce various microstructures as well as low thermal diffusivity and low thermal conductivity coatings.
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Shinmi, Akio. "Characterization of the materials used in air plasma sprayed thermal barrier coatings." Thesis, University of Manchester, 2011. https://www.research.manchester.ac.uk/portal/en/theses/characterization-of-the-materials-used-in-air-plasma-sprayed-thermal-barrier-coatings(a23aa905-e66b-48fd-8a57-5f02b7b45ce3).html.
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The degradation phenomena of the materials composing thermal barrier coatings (TBCs) have been investigated destructively and non-destructively in this dissertation. In order to make a clear explanation, the degradation phenomena of an individual material have been investigated with mainly impedance spectroscopy (IS) and indentation technique. In addition, the interfacial fracture toughness of an air plasma sprayed (APS) TBC has been measured with a four point bending test. A cold pressed and sintered YSZ sample was first used to characterise the electrical and the mechanical properties of the YSZ. The logarithmic scale of the electrical conductivity of YSZ increases with an increase of the ratio of measured hardness to its Young's modulus (H/E) until the densification stops. The variation of the microstructures, eg, grain size changes the electrical properties of YSZ.The electrical and mechanical properties of air plasma sprayed (APS) yttria stablised zirconia (YSZ) thermal barrier coatings (TBCs) were determined using impedance spectroscopy and an indentation technique, respectively. Upon thermal exprosure, sintering and phase transformation occurs in the YSZ TBCs, leading to changes in both the mechanical and electrical properties of the TBCs. After the thermal treatment, the formation of the monoclinic phase in the YSZ TBCs reduced the density of the TBCs and thus affected both the mechanical properties and conductivity of the TBCs. In this study, a relationship between the electrical and mechanical properties of APS TBCs has been established, allowing us to evaluate the properties of TBCs non-destructively with the use of impedance spectroscopy. The electrical properties of a thermally grown oxide (TGO) formed on a Fecralloy substrate was affected by the residual stress of the TGO layer. In addition, IS can distinguish the effect of grains and grain boundaries when Bode plots and modulus spectra, imaginary modulus M' vs real modulus M', were used. The conductivity and the dielectric constant of the grains in the TGO layer decreases with an increase of its compressive residual stress while the dielectric constant of the grain boundaries is almost constant regardless of the TGO residual stress. The calculated dielectric constant of the grains is slightly higher while that of the grain boundaries is slightly lower than the literature value of the dielectric constant of a pure alumina. The interfacial fracture toughnesses of an APS TBC thermally treated at 1050oC for various times were characterised using four point bending tests. The delamination occurred primarily within the TC, just several micrometres above the TGO layer. The interfacial fracture toughness increases first to a maximum after a 50h thermal treatment, and then gradually decreases with further thermal treatment. The increment of the interfacial toughness at the beginning of the thermal treatment is due to sintering while its reduction is due to the monoclinic phase formation during the thermal treatment.
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Angulo, Pedoro Antonio Diaz. "Microstructural characterization of a plasma sprayed ZrO2-Y2O3-TiO2 thermal barrier coating." Thesis, Brunel University, 1996. http://bura.brunel.ac.uk/handle/2438/6293.
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The use of plasma sprayed ceramic coats as thermal barrier coatings (TBCs) for the protection of metallic structures and equipment from severe thermal, abrasive and corrosive conditions has been documented extensively in the last two decades. The state-of-the-art TBCs consist of a double layer coat. a top ceramic layer and an intermediate bond coat (MCrAIY, M=Ni, Co, Fe) deposited on the alloy substrate. Zirconia, both stabilized and partially stabilized with different oxides has been used as the ceramic top coat due to its low thermal conductivity and low thermal expansion coefficient. Studies of the microstructure of the TBCs have shown aspects that can help the understanding of the properties of the coating. The ternary system ZrOz-Y203-TiCz is believed to offer improved properties when it is compared to Zr02-Y203. However, the use of &02-Y203-Ti02 as TBCs, a major part of this work, is not widely reported in the literature. The purpose of this thesis was to study the microstructure of a plasma sprayed ZrOrY203-TiO2 TBC using X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), and Transmission Electron Microscopy (TEM). The evolution of the Zr41_phase distribution in the ceramic coat was followed by XRD after different heat treatments, with the finding that the cooling rate plays a decisive role in the final Zr42 phase composition. SEM studies allowed a description of the lamellae structure of the Zr02-Y203-TiOz coating. The evolution of the morphology, porosity and crack distribution in the coat after different thermal treatments were followed by SEM. Evidence of incipient sintering is observed in Zr02-Y203-Ti02 coats heated at temperatures higher than 1200 °C. This should lead to poor coating performance. EDS analysis revealed an heterogeneous distribution of titanium through the oating. A detailed microstructural characterization of the as-sprayed coating was done using TEM. Microstructural features such as micro-twins, antiphase-boundaries and mottled morphology associated with "non-transformable" tetragonal ZrO2 phase were identified. It is believed that these microstructural elements promote toughening and thermal stress relief mechanisms that provide the coating with the erosion and thermal shock resistance required for a TBC. The presence of TiO2 is linked to a higher proportion of tetragonal ZrO2 in the Zr02-Y203-Ti02 coating, therefore improved properties of the coating are expected. The addition of TiO2 promotes grain growth and decreases the final density in pressed and sintered Zr02-Y203-TiO2 powders. The results obtained are a contribution to the understanding of the microstructure of TBCs and to the sparse knowledge base of the ZrOrY2O3-TiO2 coatings. Further work should be done in the characterization of the ZrO2-Y2O3-Ti42 coatings and the study of its stability under different conditions in order to determine the real potential of this material offers as an alternative to the better known ZrOrY203 TBC.
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Mc, Murchie Donald. "Development of a 1080 steel plasma sprayed coating for slide/roll wear conditions /." Full text open access at:, 1996. http://content.ohsu.edu/u?/etd,251.
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Zhao, Jian. "Modelling damage and fracture evolution in plasma sprayed ceramic coatings : effect of microstructure." Thesis, Loughborough University, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.421924.
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Park, Hyuen Me (Mia) Park. "Numerical and experimental analysis of stress behavior of plasma-sprayed Bioglass on titanium /." Full text open access at:, 1996. http://content.ohsu.edu/u?/etd,587.
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Niebuhr, David V. "Development of a self-lubricating plasma sprayed coating for rolling/sliding contact wear /." Full text open access at:, 1997. http://content.ohsu.edu/u?/etd,14.
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Hobbs, Martin K. "The structure and properties of plasma-sprayed 8% yttria-zirconia thermal barrier coatings." Thesis, University of Bath, 1989. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.234081.
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Patterson, Travis. "Effects of Internal Oxidation on Thermo-Mechanical Properties of Atmospheric Plasma Sprayed Conicraly Coatings." Master's thesis, University of Central Florida, 2008. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/2959.
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Thermal barrier coatings (TBC) with MCrAlY (M=Co and/or Ni) bond coats have been widely used in hot sections of gas turbines to protect underlying superalloys from high temperatures, oxidation, and hot corrosion. Deposition of MCrAlY bond coats using atmospheric plasma spray (APS), as oppose to conventionally employed vacuum/low-pressure plasma spray and high velocity oxy-fuel deposition, allows greater flexibility in ability to coat economically and rapidly for parts with complex geometry including internal surfaces. There were three objectives of this study. First, relationships between APS spray parameters and coating microstructure was examined to determine optimum spray parameters to deposit APS CoNiCrAlY bond coats. Second, free-standing APS CoNiCrAlY coatings were isothermally oxidized at 1124ºC for various periods to examine the evolving microstructure of internal oxidation. Third, as a function of time of isothermal oxidation (i.e., internal oxidation), thermal conductivity and coefficient of thermal expansion were measured for free-standing APS CoNiCrAlY bond coats. Thirteen CoNiCrAlY coatings were deposited on steel substrates by APS using the F4-MB plasma torch. APS CoNiCrAlY bond coats were produced by incremental variation in the flow rate of primary (argon) gas from 85 to 165 SCFH and the flow rate of secondary (hydrogen) gas from 9 to 29 SCFH. Optimum coating microstructure was produced by simultaneously increasing the flow rate of both primary and secondary gas, so that the particle temperature is high enough for sufficient melting and the particle velocity is rapid enough for minimum in-flight oxidation. Optimum spray parameters found in this study were employed to deposit free-standing APS CoNiCrAlY coatings that were isothermally oxidized at 1124ºC for 1, 6, 50,100, and 300 hours. Extent of internal oxidation was examined by scanning electron microscopy and image analysis. Internal oxidation occurred by a thickening of oxide scales segregated at the splat boundaries oriented parallel to the coating surfaces. Thermal conductivity and coefficient of thermal expansion (CTE) of the free-standing APS CoNiCrAlY coatings were measured as a function of internal oxidation (i.e., time of oxidation or extent of internal oxidation). Thermal conductivity of free-standing APS CoNiCrAlY was found to decrease with increasing internal oxidation from 28 to 25 W/m-K. This decrease is due to an increase in the amount of internal oxides with lower thermal conductivity (e.g., Al2O3). CTE of free-standing APS CoNiCrAlY, measured in temperature range of 100°~500°C, was also found to decrease with increasing internal oxidation. Internal oxides have lower CTE than metallic CoNiCrAlY coatings. These evolving properties of APS CoNiCrAlY should be beneficial to the overall performance of TBCs in gas turbine applications.M.S.M.S.E.
Department of Mechanical, Materials and Aerospace Engineering
Engineering and Computer Science
Materials Science & Engr MSMSE
30
Wang, Steven Yuan Jun. "Thermal conductivity and sintering characteristics of plasma sprayed dysprosia-yttria-zirconia thermal barrier coatings." Thesis, University of British Columbia, 2009. http://hdl.handle.net/2429/7379.
Full textAbstract:
Yttria-stabilized zirconia has long been the favoured refractory material for demanding
applications such as thermal barrier coatings on turbine components. Its low thermal
conductivity, relatively high thermal expansion coefficient, and good fracture toughness are most
useful parameters when acute thermal cycles are considered. In recent years however, the
demand for higher turbine operating temperatures has led to novel and innovative research in
improving the thermal conductivity and sintering resistance of thermal barrier coatings. Rareearth
doped zirconia, rare-earth zirconates, and lanthanum hexa-aluminate have all been
proposed as candidate materials for the next generation of thermal barrier coatings. Drawn from
research conducted during 2003-2005, this study focuses on dysprosia as a ternary dopant to
yttria-stabilized zirconia, examining the relationship of dopant content with overall thermal
conductivity and sintering behaviour under cyclic thermal loading between room temperature
and 1100°C. Air plasma spray deposition technique was employed for coatings deposition.
Based on existing published works, this study is prefaced with four hypotheses: 1. increasing
levels of dysprosia would likely result in lower overall thermal conductivity; 2. best
improvement occurs at about 10 mol% total dopant (Dy + Y); 3. addition of dysprosia is also
likely to increase sintering resistance during thermal cycling, since Dy cation radius is larger
than Zr; 4. higher dopant concentrations, between 10 mol% and 50 mol%, should increasingly
lead to shorter coating life under thermal cycling. As-sprayed coating heat capacity, thermal
diffusivity, and porosity were measured by differential scanning calorimetry, laser flash method,
and image analyses, respectively. Post-cycle coating porosity levels were compared against data
for as-sprayed coatings. A theoretical model for estimating the thermal conductivity of plasma
sprayed zirconia coatings was derived and constructed from previous works by other researchers.
Experimental data and theoretical model presented in this study offer positive confirmations for
the hypotheses, with the exceptions that the greatest reduction in thermal conductivity was seen
at 15 mol% total dopant and that increased levels of dysprosia did not result in continued
reductions in thermal conductivity. Literature data suggests long range ordering of oxygen
vacancies could be a contributing factor in this trend.
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Ahrens, Rebecca Lynn. "Modification of plasma sprayed wear and corrosion resistant coatings by high-density infrared heating." [Ames, Iowa : Iowa State University], 2007.
Find full text
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Tang, Qian. "Production and characterisation of vacuum plasma sprayed (VPS) hydroxyapatite and silicon-substituted hydroxyapatite coatings." Thesis, University of Cambridge, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.609136.
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Kadhim, Mohammed Jasim. "Laser cladding of ceramics and sealing of plasma sprayed zirconia based thermal barrier coatings." Thesis, Imperial College London, 1990. http://hdl.handle.net/10044/1/11288.
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Bargraser, Carmen. "Fatigue lifetime approximation based on quantitative microstructural analysis for air plasma sprayed thermal barrier coatings." Master's thesis, University of Central Florida, 2011. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/4731.
Full textAbstract:
The durability of thermal barrier coatings (TBCs) affects the life of the hot section engine components on which they are applied. Fatigue is the general failure mechanism for such components and is responsible for most unexpected failures; therefore it is desirable to develop lifetime approximation models to ensure reliability and durability. In this study, we first examined the microstructural degradation of air plasma sprayed ZrO[sub2]-8wt.%Y[sub2]O[sub3] TBCs with a low-pressure plasma sprayed CoNiCrAlY bond coat on an IN 738LC superalloy substrate. The durability of TBCs were assessed through furnace thermal cyclic tests carried out in air at 1100[degrees]C with a 1-, 10-, and 50-hour dwell period, preceded by a 10-minute heat-up and followed by a 10-minute forced-air-quench. Failure mechanisms of the TBCs were thoroughly investigated through materials characterization techniques including: X-Ray Diffraction, Scanning Electron Microscopy, and Energy Dispersive X-Ray Spectroscopy. Quantitative microstructural analyses were then carried out to document the growth of the thermally grown oxide (TGO) scale, the depletion of the Al-rich [Beta]-NiAl phase in the bond coat, and the population and growth of micro-cracks near the YSZ/bond coat interface. Trends in the TGO growth and the [Beta]-phase depletion in the bond coat followed those of diffusion-controlled processes—parabolic growth of the TGO and exponential depletion of the [Beta]-phase. Formation and propagation of cracks within the YSZ resulted in complete spallation of the YSZ topcoat from the bond-coated superalloy substrate. Evolution in these microstructural features was correlated to the lifetime of TBCs, which showed cracking within the YSZ to be the cause of failure; thus a lifetime approximation model was developed, via modification of Paris Law, based on the experimental data. The model predicted the TBC lifetime within 10% of the experimental lifetime.ID: 030646175; System requirements: World Wide Web browser and PDF reader.; Mode of access: World Wide Web.; Thesis (M.S.M.S.E.)--University of Central Florida, 2011.; Includes bibliographical references (p. 67-69).
M.S.M.S.E.
Masters
Materials Science Engineering
Engineering and Computer Science
Materials Science and Engineering; Accelerated BS to MS Track
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Tufekci, Eser. "Microscopic, crystallographic and adherence properties of plasma-sprayed calcium phosphate coatings on Ti-6A1-4V." The Ohio State University, 1998. http://catalog.hathitrust.org/api/volumes/oclc/48146859.html.
Full textAbstract:
Thesis (Ph. D.)--Ohio State University, 1998.Advisor: William A. Brantley, Oral Biology Program. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.
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Ntsoane, Tshepo Paul. "In-vitro investigation of air-plasma sprayed hydroxyapatite coatings deposited on two geometrically different substrates." Thesis, University of Pretoria, 2020. http://hdl.handle.net/2263/77871.
Full textAbstract:
In this study, coatings of hydroxyapatite (HAp) prepared by thermal spraying
technique are investigated for biological response. Spraying was done on two
geometrically different Ti-6Al-4V alloy substrates under atmospheric conditions.
Subsequent immersion experiments, mimicking physiological environment, were
carried out using simulated body fluids (SBF).
Non-destructive techniques utilizing conventional and high-energy synchrotron
diffractometry were employed for depth–resolved investigations of phase
composition, crystallinity and residual stresses within the coating for both substrate
geometries. Microscopy techniques were used to examine surface morphology and
microstructure.
In both substrate geometries and for all immersion periods, HAp is the predominant
phase with tetra-calcium phosphate (TTCP) and tri-calcium phosphate (TCP) the two
main thermal products. The coating deposited on cylindrical rod substrate show a
higher volume fraction of HAp at the near-surface region for the as-sprayed condition
and samples immersed for 7 and 28 days. Further immersion shows the former
decreasing gradually while the latter saturates after 28 days. Thermal products TTCP
and TCP, for the coating deposited on the flat geometry substrate decreased with
immersion, while those deposited on the cylindrical rod remains roughly the same
before increasing slightly. Through-thickness behavior shows the as-sprayed HAp
increasing almost linearly with depth, reaching a maximum around the coating
midpoint before decreasing with further depth. Immersion in SBF does not alter the
general trend across the coating however it increased the volume fraction of HAp
within the first half of the coating with the biggest change occurring between 7 and
28-days of immersion. The variation of HAp with depth and immersion at the three
lateral positions shows agreement within error bars indicating the coating to be
homogenous. The trend is observed for coating deposited on cylindrical substrate
geometry.
Both substrate geometries show high near-surface region crystallinity with an index
of ~90%. The interface region is less crystalline with a degree of crystallinity index of
67% and 56% for the flat and cylindrical substrates, respectively. Immersion in SBF
does not alter the general through-thickness trend however it increased the degree of
crystallinity at both ends.
Residual stresses for the coating deposited on both substrate geometries are tensile
and small, not exceeding 42 MPa and 65 MPa, respectively. The stresses are mainly
confined in the near-surface region with the interior region showing neglible stresses,
<10 MPa. Immersion in SBF relaxes the stress with the interior to almost zero. In the
as-sprayed condition, the magnitudes of the average normal stresses 11 and 22 are
36.1 ± 2.9 MPa and 36.2 3.0 MPa, respectively; the stresses increase by ~10%
and ~13% to 39.6 ± 2.6 MPa and 41.0 ± 2.6 MPa respectively upon immersion. With
further immersion i.e. after 28 days, they relax and stabilize around 25.6 ± 2.8 MPa
and 28.4 ± 2.8 MPa. Coatings deposited on cylindrical rod show similar trend with 11
and 22 increasing from 57.7 ± 3.2 MPa to 37.2 ± 3.1 MPa to 63.4 2.6 MPa and
41.9 3.5 MPa, respectively and subsequently decreasing 51.0 3.5 MPa and 39.3
3.3 MPa, respectively.
Microscopy analysis of the coating show typical plasma sprayed coating morphology
with glassy smooth regions, pancake splats, cracks as well as partial molten particles
across coating surface. Immersion in SBF resulted in dissolution of ions from the
coating hence increasing the surface roughness. Further immersion led to the
formation of a precipitate layer which grew in thickness with immersion period. The
precipitate extended deeper into the coating through a 3-D network of channels.
Overall, the first 7 days of immersion are crucial with SBF-induced changes of the
above-mentioned occurring during this period and the near-surface region being the
most affected. Substrate geometry seems to have an effect on the crystallinity, phase
composition, residual stress as well as their dissolution.Thesis (PhD)--University of Pretoria, 2019.
Physics
PhD
Unrestricted
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Hansel, Jason Edgar. "The Influence of Thickness on the Complex Modulus of Air Plasma Sprayed Ceramic Blend Coatings." Wright State University / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=wright1228478738.
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McNally, Claire Anne. "The laser drilling of a nickel based superalloy coated with a plasma-sprayed thermal barrier coating." Thesis, University of Nottingham, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.417417.
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Shinozaki, Maya. "The effect of sintering and CMAS on the stability of plasma-sprayed zirconia thermal barrier coatings." Thesis, University of Cambridge, 2013. https://www.repository.cam.ac.uk/handle/1810/244944.
Full textAbstract:
State of the art thermal barrier coatings (TBCs) for gas turbine applications comprise (7 wt.%) yttria partially stabilized zirconia (7YSZ). 7YSZ offers a range of attractive functional properties – low thermal conductivity, high thermal expansion coefficient and high in-plane strain tolerance. However, as turbine entry temperatures are raised, the performance of 7YSZ coatings will be increasingly affected by sintering and environmental contamination, by calcia-magnesia-alumina-silica (CMAS) deposits. The effect of sintering-induced stiffening on the driving force for spallation of plasma-sprayed (PS) TBCs was investigated. Spallation lifetimes of TBC specimens sprayed onto alumina substrates were measured. A simple fracture mechanics approach was employed in order to deduce a value for the strain energy release rate. The critical strain energy release rate was found to be constant, and if this value had been known beforehand, then the rationale presented here could be used for prediction of coating lifetime. The effect of vermiculite (VM) and volcanic ash (VA) contamination on the sintering-induced spallation lifetime of PS TBCs was also investigated. The presence of both VM and VA was found to accelerate the rise in their Young’s modulus with sintering. Spallation results show that coating lifetime may be significantly reduced, even at relative low addition levels, due to the loss of strain tolerance caused by the penetration of glassy deposits. This result gives a clear insight into the role CMAS plays in destabilizing TBCs. Finally, the adhesion characteristics of ingested volcanic ash were studied using a small jet engine. The effects of engine speed and particle size were investigated. Deposition on turbine surfaces was assessed using a borescope. Deposition mainly occurred on the nozzle guide vane and blade platform. A numerical model was used to predict particle acceleration and heating in flight. It was observed that larger particles are more likely to adhere because they have greater inertia, and thus are more likely to impact surfaces. The temperature of the larger particles at the end of its flight was predicted to be below its softening point. However, since the component surface temperatures are expected to be hotter, adhesion of such particles is probable, by softening/melting straight after impact.
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Howells, Richard. "Plasma sprayed NiCoCrAlY bond coats : measurement of mechanical properties and residual stresses during first heating after deposition." Thesis, University of Oxford, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.393458.
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Bakshi, Srinivasa R. "Plasma And Cold Sprayed Aluminum Carbon Nanotube Composites: Quantification Of Nanotube Distribution And Multi-Scale Mechanical Properties." FIU Digital Commons, 2009. http://digitalcommons.fiu.edu/etd/97.
Full textAbstract:
Carbon nanotubes (CNT) could serve as potential reinforcement for metal matrix composites for improved mechanical properties. However dispersion of carbon nanotubes (CNT) in the matrix has been a longstanding problem, since they tend to form clusters to minimize their surface area. The aim of this study was to use plasma and cold spraying techniques to synthesize CNT reinforced aluminum composite with improved dispersion and to quantify the degree of CNT dispersion as it influences the mechanical properties. Novel method of spray drying was used to disperse CNTs in Al-12 wt.% Si pre-alloyed powder, which was used as feedstock for plasma and cold spraying. A new method for quantification of CNT distribution was developed. Two parameters for CNT dispersion quantification, namely Dispersion parameter (DP) and Clustering Parameter (CP) have been proposed based on the image analysis and distance between the centers of CNTs. Nanomechanical properties were correlated with the dispersion of CNTs in the microstructure. Coating microstructure evolution has been discussed in terms of splat formation, deformation and damage of CNTs and CNT/matrix interface. Effect of Si and CNT content on the reaction at CNT/matrix interface was thermodynamically and kinetically studied. A pseudo phase diagram was computed which predicts the interfacial carbide for reaction between CNT and Al-Si alloy at processing temperature. Kinetic aspects showed that Al4C3 forms with Al-12 wt.% Si alloy while SiC forms with Al-23wt.% Si alloy. Mechanical properties at nano, micro and macro-scale were evaluated using nanoindentation and nanoscratch, microindentation and bulk tensile testing respectively. Nano and micro-scale mechanical properties (elastic modulus, hardness and yield strength) displayed improvement whereas macro-scale mechanical properties were poor. The inversion of the mechanical properties at different scale length was attributed to the porosity, CNT clustering, CNT-splat adhesion and Al4C3 formation at the CNT/matrix interface. The Dispersion parameter (DP) was more sensitive than Clustering parameter (CP) in measuring degree of CNT distribution in the matrix.
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Balani, Kantesh. "Role of carbon nanotube dispersion in fracture toughening of plasma sprayed aluminum oxide - carbon nanotube nanocomposite coating." FIU Digital Commons, 2007. http://digitalcommons.fiu.edu/etd/1380.
Full textAbstract:
Aluminum oxide (A1203, or alumina) is a conventional ceramic known for applications such as wear resistant coatings, thermal liners, heaters, crucibles, dielectric systems, etc. However applications of A1203 are limited owing to its inherent brittleness. Due to its excellent mechanical properties and bending strength, carbon nanotubes (CNT) is an ideal reinforcement for A1203 matrix to improve its fracture toughness.
The role of CNT dispersion in the fracture toughening of the plasma sprayed A1203-CNT nanocomposite coating is discussed in the current work. Pretreatment of powder feedstock is required for dispersing CNTs in the matrix. Four coatings namely spray dried A1203 (A-SD), A1203 blended with 4wt.% CNT (A4C-B), composite spray dried A1203-4wt.% CNT (A4C-SD) and composite spray dried A1203-8wt.% CNT (A8CSD), are synthesized by plasma spraying. Owing to extreme temperatures and velocities involved in the plasma spraying of ceramics, retention of CNTs in the resulting coatings necessitates optimizing plasma processing parameters using an inflight particle diagnostic sensor. A bimodal microstructure was obtained in the matrix that consists of fully melted and resolidified structure and solid state sintered structure. CNTs are retained both in the fully melted region and solid-state sintered regions of processed coatings.
Fracture toughness of A-SD, A4C-B, A4C-SD and A8C-SD coatings was 3.22, 3.86, 4.60 and 5.04 MPa m1/2 respectively. This affirms the improvement of fracture toughness from 20 % (in A4C-B coating) to 43% (in A4C-SD coating) when compared to the A-SD coating because of the CNT dispersion. Fracture toughness improvement from 43 % (in A4C-SD) to 57% (in A8C-SD) coating is evinced because of the CNT content. Reinforcement by CNTs is described by its bridging, anchoring, hook formation, impact alignment, fusion with splat, and mesh formation.
The A1203/CNT interface is critical in assisting the stress transfer and utilizing excellent mechanical properties of CNTs. Mathematical and computational modeling using ab-initio principle is applied to understand the wetting behavior at the A1203/CNTinterface. Contrasting storage modulus was obtained by nanoindentation (~ 210, 250, 250-350 and 325-420 GPa in A-SD, A4C-B, A4C-SD, and A8C-SD coatings respectively) depicting the toughening associated with CNT content and dispersion.
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Zubacheva, Oxana A. "Plasma sprayed and physically vapor deposited thermal barrier coatings: comparative analysis of thermoelastic behavior based on curvature studies." kostenfrei, 2004. http://deposit.ddb.de/cgi-bin/dokserv?idn=972727434.
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Li, Chun. "Measurement and understanding the residual stress distribution as a function of depth in atmosphere plasma sprayed thermal barrier coatings." Thesis, University of Manchester, 2018. https://www.research.manchester.ac.uk/portal/en/theses/measurement-and-understanding-the-residual-stress-distribution-as-a-function-of-depth-in-atmosphere-plasma-sprayed-thermal-barrier-coatings(e4dd38cc-2800-4719-bfe5-cccd0d6ff8c8).html.
Full textAbstract:
Residual stresses are generally considered to be the driving forces for the failure of APS TBCs. In this thesis, the residual stress distribution as a function of depth in APS TBC has been measured by synchrotron XRD and explained by image based modelling based on the microstructure detailed studied by SEM and CT. The residual stress/ strain distribution as a function of depth was measured by synchrotron XRD in transmission and reflection geometry. The residual stress/ strain values were analysed using full pattern Rietveld refinement, the sin square psi method and XRD2 method. For the reflection geometry, a new method was developed to deconvolute the residual stress value in each depth from the measured averaged values. Two types of residual stress/strain distribution were observed. The first kind of residual stress was found to be compressive and followed a non-linear trend, which increased from the surface to the interface, decreased slightly and increased again to the interface. This trend showed a jump feature near the interface. The second kind of residual stress distribution possessed two jump features: one near the interface similar to the first kind and another jump feature near the sample surface. The residual stress in both beta and gama phase in the bond coat were also investigated which showed a tensile stress state. The stress trend predicted by our analytical model followed a linear relationship. Comparing this with the first kind of residual stress distribution, two main differences were shown. Firstly the jump feature near the interface and secondly the much larger overall stress gradient. The 3D and 2D microstructure of the sample with the first kind of residual stress distribution was observed by X-ray CT and SEM. The effect of pores, inter-splat cracks and the rumpling interface on the residual stress distribution was investigated by image based modelling. It was proved that the pores and the inter-splat cracks had no large influence on the stress distribution and the jump feature near the interface was a result of the rumpling interface. The much larger stress gradient observed in the measured residual stress distribution was an indication of the stress relaxation in the coating which was proved by a specially designed mechanical test. To explain the jump feature near the sample surface in the second kind of stress distribution. 3D microstructures of the measured samples were observed using X-ray CT. The effect of vertical and the side cracks on the stress distribution were investigated by image based modelling. It was found that the vertical crack had no large influence on the residual stress distribution and the jump feature in the stress trend near the surface could be attributed to the side crack. The effect of other kinds of cracks that were not directly observed in our samples, such as middle or through side cracks, were also investigated. These results were used to develop a semi-destructive method to determine the existence and distribution of cracks in APS TBC.
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Patel, Pravinkumar M. "An evaluation of the technique of photothermal radiometry for the non-destructive testing and characterisation of plasma-sprayed coatings." Thesis, University of Bath, 1988. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.384104.
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Najafi, Ehsan. "Understanding the effect of material composition and microstructure on the hot corrosion behaviour of plasma sprayed thermal barrier coatings." Thesis, Högskolan Väst, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT), 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:hv:diva-14532.
Full textAbstract:
Thermal barrier coatings (TBC) are used in the hot sections of gas turbine engine in order to insulate the substrate at high temperature. Molten salt infiltration retards the durability of TBCs. The current standard material, i.e. 8YSZ is susceptible to molten salt infiltration. Therefore, alternate TBC materials are desirable. In addition to material composition, the TBC microstructure plays an important role in mitigating molten salt infiltration. Therefore, in this work, three different TBC variations were investigated. The first variation was a columnar microstructured 48YSZ TBC processed by SPS (48YSZ-SPS). The second variation was a columnar microstructured 8YSZ TBC processed by SPS (8YSZ-SPS), and the third variation was a lamellar microstructured 8YSZ TBC deposited by APS (8YSZ-APS). The as-sprayed TBC specimens were characterized by SEM/EDS, porosity analysis and XRD measurements. Later, the TBC specimens were exposed to hot corrosion test and their interaction with the molten salts were investigated using SEM (EDS and XRD). It was shown that an increase in stabilizer content (yttria content) in zirconia (in the case of 48YSZ) leads to an improved hot corrosion resistance due to the adequate amount of yttria content, which restricts the molten salt infiltration by forming needle like YVO4 phase. In terms of microstructure comparison, the infiltration behavior was similar for columnar microstructured 8YSZ and lamellar microstructured 8YSZ-APS as the molten salts infiltrated the coatings completely compared to the 48YSZ TBC. Furthermore, it seems that the molten salt infiltrates the TBC through globular pores, delamination cracks and splat boundaries in the case of APS-TBCs whereas the column gaps favor easier infiltration of molten salts in the case of columnar microstructured SPS processed TBCs.
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Zhang, Bochun. "Failure Mechanism Analysis and Life Prediction Based on Atmospheric Plasma-Sprayed and Electron Beam-Physical Vapor Deposition Thermal Barrier Coatings." Thesis, Université d'Ottawa / University of Ottawa, 2017. http://hdl.handle.net/10393/35709.
Full textAbstract:
Using experimentally measured temperature-process-dependent model parameters, the failure analysis and life prediction were conducted for Atmospheric Plasma Sprayed Thermal Barrier Coatings (APS-TBCs) and electron beam physical vapor deposition thermal barrier coatings (EB-PVD TBCs) with Pt-modified -NiAl bond coats deposited on Ni-base single crystal superalloys. For APS-TBC system, a residual stress model for the top coat of APS-TBC was proposed and then applied to life prediction. The capability of the life model was demonstrated using temperature-dependent model parameters. Using existing life data, a comparison of fitting approaches of life model parameters was performed. The role of the residual stresses distributed at each individual coating layer was explored and their interplay on the coating’s delamination was analyzed. For EB-PVD TBCs, based on failure mechanism analysis, two newly analytical stress models from the valley position of top coat and ridge of bond coat were proposed describing stress levels generated as consequence of the coefficient of thermal expansion (CTE) mismatch between each layers. The thermal stress within TGO was evaluated based on composite material theory, where effective parameters were calculated. The lifetime prediction of EB-PVD TBCs was conducted given that the failure analysis and life model were applied to two failure modes A and B identified experimentally for thermal cyclic process. The global wavelength related to interface rumpling and its radius curvature were identified as essential parameters in life evaluation, and the life results for failure mode A were verified by existing burner rig test data. For failure mode B, the crack growth rate along the topcoat/TGO interface was calculated using the experimentally measured average interfacial fracture toughness.
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Selecman, Audrey Marie. "Evaluation of osseointegration between two different modalities of hydroxyapatite implant surface coatings plasma sprayed HA coated implants and electrophoresis deposited nano HA coated implants /." View the abstract Download the full-text PDF version, 2007. http://etd.utmem.edu/ABSTRACTS/2007-008-Selecman-index.html.
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Thesis (M.S. )--University of Tennessee Health Science Center, 2007.Title from title page screen (June 30, 2008). Research advisor: Joo L. Ong, Ph.D. Document formatted into pages (vi, 47 p. : ill.). Vita. Abstract. Includes bibliographical references (p. 41-46).
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VALERETO, IVONE de C. L. "Caracterizacao de implantes dentais da liga Ti6Al7Nb revestidos por hidroxiapatita pela tecnica plasma-spray." reponame:Repositório Institucional do IPEN, 1998. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10722.
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Made available in DSpace on 2014-10-09T12:43:21Z (GMT). No. of bitstreams: 0Made available in DSpace on 2014-10-09T13:56:45Z (GMT). No. of bitstreams: 1 06435.pdf: 7431452 bytes, checksum: 52a613c5fd6687de6ee09e587bde83c2 (MD5)
Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
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Pons, Elodie. "Propriétés d’adhérence de revêtements projetés plasma sur substrats fragiles : caractérisation et identification de lois d’interface par Modèles de Zones Cohésives." Thesis, Université Grenoble Alpes (ComUE), 2016. http://www.theses.fr/2016GREAI003/document.
Full textAbstract:
La rupture adhésive est un mécanisme de défaillance fréquemment observé sur les structures multicouches et les pièces revêtues dans les technologies actuelles telles que la microélectronique, le biomédical ou l’aérospatial. Selon l’application visée et les sollicitations en service rencontrées, des propriétés d’adhérence minimales sont attendues.Le CEA Le Ripault étudie la tenue mécanique de systèmes revêtement/substrat. Deux assemblages constitués d’un revêtement projeté plasma, l’un céramique et l’autre métallique, sur un substrat fragile en céramique sont étudiés. Ces revêtements disposent d’une microstructure et de propriétés mécaniques bien spécifiques liées au procédé d’élaboration. L’un des objectifs de cette thèse est de caractériser et quantifier l’adhérence des revêtements projetés plasma aux moyens d’essais mécaniques. Classiquement, les essais d’adhérence sont largement développés pour l’étude de l’adhérence de revêtements céramiques sur substrats ductiles, pour des applications de type barrières thermiques. Or la grande fragilité des substrats et des revêtements représente des difficultés supplémentaires à la mise en œuvre des essais d’adhérence. Afin de prévenir la rupture cohésive du substrat, les essais nécessitent un effort d’adaptation tenant compte des contraintes dimensionnelles et matérielles imposées par l’assemblage. Par ailleurs, afin de caractériser intégralement l’adhérence, différents modes de sollicitation sont balayés à travers différents essais d’adhérence : traction, cisaillement bi-entaillé, clivage en coin, flexion 4 points sur éprouvette entaillée, four-point bend End Notched Flexure test (4-ENF),…Le second objectif est de prédire l’amorçage et la propagation de fissures à l’interface afin de garantir la tenue mécanique des assemblages. Pour cela, une stratégie d’identification d’une loi d’interface, décrivant son comportement à la rupture, est proposée. Les Modèles de Zones Cohésives (MZC) sont adoptés pour modéliser le délaminage, sous le code éléments finis ABAQUS, à l’aide d’une loi traction-séparation bilinéaire. La comparaison entre les réponses macroscopiques numérique et expérimentale de chacun des essais d’adhérence effectué permet de calibrer chaque paramètre de la loi cohésive. Ainsi, la démarche expérimentale et numérique couplée permet d’obtenir des scénarios de rupture conformes aux observations expérimentales et d’évaluer l’intégrité de la structure soumise à une sollicitation thermique ou mécanique donnéeInterfacial cracking is a recurrent failure mechanism observed in multilayer structures and coating systems using in various fields as microelectronics, biomedical engineering or aerospace. According to the aimed application and operating loadings, a minimum adhesion of the interface is expected.CEA Le Ripault studies the mechanical strength of coating/substrate systems. Two multilayer structures made of plasma sprayed coating layer, one ceramic and the other metallic, on a brittle ceramic substrate are studied. These plasma sprayed coatings have specifics microstructure and mechanicals properties linked to manufacturing process.One of the purposes of this work is to characterize and quantify plasma sprayed coatings adhesion through mechanical tests. Adhesion tests are widely developed for study the adhesion of ceramic coatings on ductile substrates for thermal barrier coatings applications. However the high brittleness of substrates and coatings constitutes an additional difficulty to implement adhesion tests. In order to prevent cohesive failure in substrate, adhesion tests require an adaptation taking materials and dimensionals constraints into account. Furthermore, in order to fully characterize the adhesion, different loadings modes are scanned through various adhesion tests: tensile test, shear test, wedge test, four-point bending test, 4-ENF…The second purpose is to predict crack initiation and propagation along the interface in order to guarantee multilayer mechanical strength. In that purpose, an interfacial law identification strategy is proposed to describe failure behavior. A Cohesive Zone Model (CZM) is adopted to model the delamination, using the finite element code ABAQUS, with a bilinear traction-separation law. The numerical and experimental macroscopic response comparison of each performed adhesion test allows to identify one cohesive law parameter. Thus, the coupled approach allows to model failure scenario in good agreement with experimental observations and assess the integrity of the assembled structure under a thermal or a mechanical loading