No description available.

Reactive Plasma Spraying (RPS) with a hydrocarbon gas has been studied as a method to improve the mechanical properties of a commercially available 80:20 nickel-chromium alloy, and subsequently as a method to reduce the oxygen content of sprayed MCrAlY coatings. A conventional d.c. plasma torch has been modified by attaching a conical graphite tube (reactor) onto the end of the gun. The powder is then sprayed through the reactor with injected reactive hydrocarbon gas. The reactor shrouds the plasma flame from the external atmosphere and contains the desirable inner atmosphere necessary for RPS. When spraying using a reactor and reactive gas the plasma environment is changed significantly. Work has been carried out to establish the effect various spray parameters have on the final coating such that new parameters can be selected which maximise the coatings quality and performance Reactively sprayed 80: 20 Ni/Cr coatings have been produced with an in- stiu carbide reinforcing phase, leading to greatly improved wear properties compared with conventionally sprayed coatings. Reactively sprayed MCrAlY coatings have been deposited with an order of magnitude reduction in oxide levels, leading to considerably fewer line defects such as oxide stringers and delarninations. An attempt has been made with the aid of computational fluid dynamics software, to model phenomenon occurring inside the reactor section as a method to appraise reactor design and suggest further design improvements.

No description available.

Submitted by Maike Costa (maiksebas@gmail.com) on 2017-05-30T14:03:26Z No. of bitstreams: 1 arquivototal.pdf: 3595054 bytes, checksum: 5660310170d823982bf9be6c6ce622e0 (MD5) / Made available in DSpace on 2017-05-30T14:03:26Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 3595054 bytes, checksum: 5660310170d823982bf9be6c6ce622e0 (MD5) Previous issue date: 2015-07-27 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPq / By the excellent properties that present, the quasicrystals come if showing excellent protectors of metallic surfaces and their study as surface coatings is growing increasingly. In this work, was sprayed quasicrystals for methods HVOF an HVOF, in Steel substrata 1020, covers and aluminum.. In some samples, a Cu9Al4 alloy was sprayed between the substratum and the quasicristalino covering, to try to improve the adherence of the covering to the substratum and to protect the Quasicrystalline layer of contaminations. The coverings were characterized by the technique of DRX, optical microscopy and SEM. The study of microhardness and nanohardness in the surfaces of sprayed coverings was made. Finally, a tribological study of coatings was accomplished to evaluate the behavior of wear and friction of the layers and the adherence between them and substrata. These results will provide the basis for the use of these materials in parts and equipment used in industries. The layers obtained for LVOF had showed to one high degree of oxidation and a bad adherence with the substratum. The coverings obtained for HVOF had showed one high micro-hardness, with values between of 600 and 800HV. The values of nano hardness and modulus of elasticity that was found in the coatings are in accordance with the values found in literature. For the test of risk with spherical tip of 800μm, the critical loads of the risks were of 20N, for all the samples with exception of the Al-Qc sample. It did not have pullout in respect to substrate of coverings with 100μm of thickness and the results of the risk essays, was the same, independent of its nature, indicating that, for a thickness of 100μm, the quasicrystalline coatings behave as a massive material, facilitating the protection of the interfaces. Through the simulation tests, we could see that during the tests, for coatings with thicknesses of 100μm, the interfaces practically remain intact and they do not suffer plastic deformations. The simulation results corroborate with the tests of risks confirming that for a thickness of 100μm, the coverings behave as a massive material, independent of the nature of the substratum. / Pelas excelentes propriedades que apresentam, os quasicristais vem se mostrando ótimos protetores de superfícies metálicas e seu estudo como revestimentos superficiais vem crescendo cada vez mais. Neste trabalho aspergimos quasicristais pelos métodos LVOF e HVOF, em substratos de Aço 1020, cobre e alumínio. Em algumas amostras, um intermetálico de Cu9Al4 foi aspergido entre o substrato e o revestimento quasicristalino, para tentar melhorar a aderência do revestimento ao substrato e proteger os revestimentos quasicristalinos de contaminações. Os revestimentos foram caracterizados pela técnica de DRX, microscopia ótica e MEV. Foi feito o estudo de micro e nanodureza nos revestimentos aspergidos. Por último, foi realizado um estudo tribológico nos revestimentos, para se avaliar o comportamento de atrito, desgaste das camadas e aderência entre elas e os substratos. Estes resultados darão base para o uso desses materiais em peças e equipamentos utilizados nas indústrias. As camadas obtidas por LVOF mostraram um alto grau de oxidação e uma aderência ruim com o substrato. Os revestimentos obtidos por HVOF mostraram uma elevada microdureza, com valores entre 600 e 800HV. Os valores de nanodureza e módulo de elasticidade encontrados nos revestimentos estão de acordo com os valores encontrados na literatura. Pelo ensaio de risco com ponta esférica de 800μm, a carga crítica dos riscos foi de 20N, para todas as amostras com exceção da amostra Al-Qc. Não houve descolamento em relação aos substratos, dos revestimentos com 100μm de espessura e os resultados dos ensaios de risco foram os mesmos, independentemente da sua natureza, indicando que, para uma espessura de 100μm, os revestimentos quasicristalinos se comportam como um material maciço, facilitando a proteção das interfaces. Através dos ensaios de simulação, pudemos ver que, para revestimentos com espessuras de 100μm, as interfaces não sofreram deformações plásticas. Os resultados de simulação confirmaram que, para uma espessura de 100μm, os revestimentos se comportam como um material maciço, independente da natureza do substrato.

Submitted by Celso Diniz (cdiniz.fatec@hotmail.com) on 2018-04-11T18:18:33Z No. of bitstreams: 1 Dissertação- Diniz versão rev 22-FINAL 03-04-2018.pdf: 4564957 bytes, checksum: 4d2c8bf606da87389121421a604f73e2 (MD5) / Approved for entry into archive by Pamella Benevides Gonçalves null (pamella@feg.unesp.br) on 2018-04-12T12:46:53Z (GMT) No. of bitstreams: 1 diniz_c_me_guara.pdf: 4564957 bytes, checksum: 4d2c8bf606da87389121421a604f73e2 (MD5) / Made available in DSpace on 2018-04-12T12:46:53Z (GMT). No. of bitstreams: 1 diniz_c_me_guara.pdf: 4564957 bytes, checksum: 4d2c8bf606da87389121421a604f73e2 (MD5) Previous issue date: 2018-02-21 / Aços inoxidáveis martensíticos, contendo 12-13% de cromo, 2-5% de níquel e menos de 0,06% de carbono, vem sendo utilizados desde a década de 60, por exemplo, na fabricação de equipamentos hidráulicos, tais como turbinas, bombas e propulsores. Aços como o ASTM A743 CA-6NM, temperados e revenidos, passam por processos de tratamento de superfície, visando aumentar a resistência à erosão e corrosão, pois devem, operar sob condições de alta agressividade. Dentre as técnicas utilizadas para revestimento de superfície, a aspersão térmica, HVOF (Hight Velocity Oxigen Fuel), é um processo altamente utilizado, por sua viabilidade técnica e econômica. Atualmente, o aço ASTM A743 CA-6NM com revestimento do tipo WC-10Co-4Cr, com espessura em torno de 100 e 200 µm, é o material mais empregado nos diversos equipamentos hidráulicos, tais como: rotores de bombas, pás de turbinas e hélices navais. O conhecimento das características microestruturais do revestimento e de seu comportamento com relação à corrosão são de grande importância na definição dos parâmetros para a realização da aspersão térmica, gerando economia e qualidade do revestimento. Neste trabalho são realizadas análises por microscopia óptica e microscopia eletrônica de varredura com EDS sobre os revestimento aspergido com WC-10Co-4Cr, visando estudar os parâmetros relacionados à porosidade e composição da microestrutura. Além disso, foram realizadas análises da dureza, ao longo de todo o revestimento, visando estabelecer correlação com as análises obtidas por microscopia, e análise eletroquímica com o intuito de compreender o comportamento do revestimento em meio salino NaCl 3,5% ( mm); todas as imagens adquiridas, passaram por processamento digital. Os resultados demonstraram que os revestimentos obtidos com 6 passes (W6) ou 8 passes (W8) apresentaram baixa porosidade, menor que 2%, sendo que os poros medidos no revestimento W6 apresentaram menor diâmetro de Feret e maior circularidade. A análise com durômetro revelou um comportamento similar dos revestimentos, com valores de dureza praticamente idênticos ao longo da espessura das camadas aspergidas. Os ensaios eletroquímicos, mostraram que o substrato apresentou corrosão puntiforme (pite) após imersão por 5, 20 e 30 h, em solução de NaCl 3,5% (mm), resultado típico para este material. Enquanto os revestimentos W6 e W8, que dentro das especificações dos ensaios, apresentaram comportamentos idênticos, nas análises com circuito aberto e curva de polarização, se mostraram revestimentos com proteção contra a corrosão. / Martensitic stainless steels, containing 12-13% chromium, 2-5% nickel and less than 0.06% carbon, have been used since the 1960s, for example, in the manufacture of hydraulic equipment such as turbines, pumps and propellers. The steels ASTM A 743 CA-6NM, in quenched and tempered conditions, undergo surface treatment processes to increase resistance to erosion and corrosion, once they do operate under conditions of high aggressiveness. Among techniques used for surface coating, thermal spraying, HVOF (Hight Velocity Oxigen Fuel), is a highly utilized process, due to its technical and economical viability. Currently, ASTM A743 CA-6NM steel with WC-10Co-4Cr type coating, with a thickness of 100 m and 200 m, is the most used material in the various pieces of equipment, such as: pump rotors, naval blades and propellers. The knowledge of the microstructural characteristics of the coating and its behavior in relation to corrosion are of great importance, in the definition of the parameters for the realization of the thermal spray, generating economy and quality of the coating. In this paper, optical microscopy and scanning electron microscopy with EDS, on WC-10Co-4Cr sputtering coatings were carried out to study the parameters related to the porosity and microstructure composition. In addition, hardness analyses were performed throughout the coating, to establish correlation with microscopic analysis and electrochemical analysis in order to understand the behavior of the coating in saline solution NaCl 3.5% (wt/wt); all images acquired, passed by digital processing images. The results showed that the coatings obtained with 6 passes (W6) or 8 passes (W8) presented low porosity, less than 2%, and the pores measured in the W6 coating presented smaller Feret diameter and greater circularity. Dilution analysis revealed a similar behavior of the coatings, with hardness values practically identical across the thickness of the sprayed layers. The electrochemical tests showed that the substrate presented punctiform corrosion (pite) after 5, 20 and 30h immersion in NaCl solution 3.5% (wt/wt); result for this material. While the W6 and W8 coatings, which presented identical behavior in the open circuit analysis and polarization curve, within the test specifications, corrosion resistant coatings were found.

Das thermische Spritzen ist ein industrieller Beschichtungsprozess, der hauptsächlich zum Schutz oder zur Funktionalisierung von Bauteiloberflächen eingesetzt wird. In der Regel werden mit diesem Verfahren Schichten mit einer Dicke von 50 bis zu einigen 100 Mikrometern aufgetragen, die überwiegend durch mechanische Verklammerung haften, wodurch die Materialeigenschaften des Bauteils weitgehend erhalten bleiben. Mit der Einführung von Suspensionen als neue Kategorie der Spritzzusätze etabliert sich gerade eine der weitreichendsten Innovationen der letzten Jahre auf dem Gebiet des thermischen Spritzens. Suspensionen sind Stoffgemische, die aus einer feindispersen, festen Phase, dem Schichtwerkstoff, und einer flüssigen Phase als Trägermedium bestehen. Damit können Partikel mit geringerer Größe in den Beschichtungsprozess eingebracht werden, so dass sich dünnere Schichten und feinere Mikrostrukturen realisieren lassen. Das thermische Spritzen mit Suspensionen erweitert damit den Anwendungsbereich und bildet eine Brückentechnologie zu den Vakuum- Dünnschichtverfahren. Im Fokus dieser Arbeit stehen die drei wichtigen keramischen Werkstoffe Aluminiumoxid, Chromoxid und yttriumstabilisiertes Zirkonoxid, die in der Form von wasserbasierten Suspensionen als Spritzzusätze für das Atmosphärische Plasmaspritzen (APS) und das Hochgeschwindigkeitsflammspritzen (HVOF) verwendet werden. Für die Injektion der Suspension in das Plasma oder die Flamme wird ein automatisiertes Suspensionsfördersystem verwendet. Darüber hinaus werden spezielle mehrteilige Injektoren entwickelt und getestet. Es werden neue Erkenntnisse zur statistischen Auswertung der Zusammenhänge zwischen den Injektionsparametern, den messbaren Eigenschaften der Tropfenwolke während der Zerstäubung, den Partikeleigenschaften im Spritzstrahl und den daraus resultierenden Schichteigenschaften vorgestellt. Dafür wurde eine neue Kenngröße für den Beschichtungserfolg, ein sogenannter Beschichtungsfaktor, hergeleitet, der sich mit vergleichsweise geringem Aufwand bestimmen lässt und außerdem die zusätzlichen Prozessvariablen beim Suspensionsspritzen mit berücksichtigt. Im Anschluss werden Beispiele für wasserbasierte, suspensionsgespritzte Schichten aus den drei keramischen Werkstoffen vorgestellt, bei denen durch entsprechende Charakterisierungsmethoden das Anwendungspotential im Vergleich zu Spritzschichten nach dem Stand der Technik verdeutlicht wird. Die Anwendungsgebiete umfassen dabei die elektrische Isolation, den Verschleißschutz sowie die thermische Isolation. Den Abschluss der Arbeit bildet eine kritische Diskussion der Eignung von wasserbasierten Suspensionen für das thermische Spritzen mit Plasma- und Flammspritzprozessen. Es werden die Vor- und Nachteile dieser Beschichtungstechnik analysiert und Verbesserungsvorschläge sowohl für die weitere Suspensions- als auch für die Anlagenentwicklung unterbreitet.

Sacrificial metallic coatings have been used in the past, for protecting steel in industrial and urban developments. It has been suggested that thermally sprayed aluminium coatings, immersed in marine environments, are also capable of protecting steel by providing galvanic protection. Researchers have also speculated that the growth of inert oxide products, on top of the coating as well as inside pores and cracks, could enhance even further its protective “shielding” properties. In addition, the self-healing abilities of the coatings, in case of mechanically induce damage, are still a matter of debate. This research project takes a critical look at these assumptions, focusing on the electrochemical response of aluminium metal sprayed (AMS) coatings immersed in 0.6 M NaCl and 0.6 M Na2SO4 solutions, in order to investigate how the presence of chlorides can alter the corrosion behaviour of these coatings. For such, a thin aluminium protective coating was deposited over two different panels (aluminium 1050 and low carbon steel), by the steel making company Fairfield-Mabey, using electric arc thermal spraying (TS). Subsequently, the coated panels were sectioned into smaller specimens, and with the aid of a SEM/EDS, and XRD, observations and analysis were conducted in their surfaces and cross sections, in order to determine the morphology, quality of deposition, and chemical composition of the coatings. Internal porosity/oxide growth after immersion, was studied using 3-D X-ray tomography scanning. Furthermore, the electrochemical behaviour of the coatings (intact and scribed) was also investigated, initially by analyzing the evolution of the open circuit potential in time, when immersed in chloride rich and chloride free environments. Additionally, the anodic polarization behaviour of the substrate and coatings were simultaneously analyzed, by connecting a zero resistance ammeter (ZRA) with the W.E. terminal of a potentiostat. To conclude, EIS and Rp vs. time plots were made in order to corroborate the data obtained from other tests. Results show that although the coating can generate superficial and internal corrosion products, these oxides are not isolating in nature nor will enhance its protective properties. On the other hand, the corrosion potential behaviour of the coatings revealed that AMS coatings have a more active than the substrate; regardless of the environment in which they were immersed or their substrate. Nevertheless, it was also observed that AMS coatings deposited onto steel will corrode faster than their substrates, and for that matter capable of offering corrosion protection, exclusively if chlorides are present in the solution.

This thesis deals with the issue of thermal spraying by means of an electric arc. First of all, a theoretical part is processed using a literary study dealing with corrosion and thermal spraying technology. The experimental part contains a description of the technological procedure and evaluation of four thermally sprayed samples. Zinacor 850, consisting of 85% zinc and 15% aluminum, was used as a coating. The evaluation involves measurements of thickness, adhesion and roughness as well as the macro-structural analysis of the coating. Two samples showed unusually low adhesion, and all samples also had a large fluctuation of the measured thicknesses. This was also confirmed by the macro-structural analysis, which showed that the sample with low adhesion also had high porosity. These defects may have multiple causes, but the recommendation for further practice is to reduce the spraying distance from the base material.

The project elaborated as a part of engineering studies branch M2307: Engineering Technology, Specialization 02: Forming and Welding Technology deals with the optimization of arc spraying parameters for TAFA 9935 facility.The theoretical part presents the principle of arc spraying, the description of the technological process and the types of additional materials. The practical part proposes the diffrent possibilities of TAFA 9935 arc spraying facility and the suitable additional materials. Several samples with diffrent parameters of spraying were created in order to test and analyse the coating quality.

Master’s thesis deals with the problems of the inner surface finish design for the CASTOR container. In the theoretical part are analyzed properties of metallic surfaces with their defects and various options of surface finishes for increased protection. The practical part of the thesis is focused on the design of appropriate technologies for specific requirements of the surface finish for the CASTOR container, creating test samples and their evaluation.