Submitted by Maria Medeiros (maria.dilva1@ufcg.edu.br) on 2018-09-27T15:03:02Z No. of bitstreams: 1 VALMIR RODRIGUES BATISTA - DISSERTAÇÃO (PPG-CEMat) 2011.pdf: 9226631 bytes, checksum: bde44a49a9cb7e76d5b2b88abf48d037 (MD5) / Made available in DSpace on 2018-09-27T15:03:02Z (GMT). No. of bitstreams: 1 VALMIR RODRIGUES BATISTA - DISSERTAÇÃO (PPG-CEMat) 2011.pdf: 9226631 bytes, checksum: bde44a49a9cb7e76d5b2b88abf48d037 (MD5) Previous issue date: 2011-08-12 / CNPq / A necessidade de exploração de óleos mais pesados, em poços cada vez mais profundos e em ambientes mais agressivos tem causado falhas dos materiais por corrosão com grandes prejuízos econômicos e ambientais. Portanto este trabalho teve como objetivo avaliar a influência dos parâmetros de soldagem sobre a geometria (razão entre a altura e a largura- R/L), diluição(D), teor de Ferro, %Fe, e consequentemente resistência à corrosão de revestimentos de ligas de Ni (Hastelloy-276) aplicados por soldagem em aços C-Mn. O processo de soldagem utilizado foi ao Arco Submerso utilizando um arame eletrodo de liga de níquel (Ni-Cr-Mo-4) com diâmetro de 1,14 mm, avaliando duas modalidades de corrente, a corrente pulsada e a corrente convencional. Como substrato foi empregado segmentos de um tubo de aço de especificação API 5L Gr B com espessura de 18 mm e diâmetro interno de 290 mm. Para relacionar a influência das variáveis citadas com as respostas desejadas, foi utilizada a técnica de planejamento de experimentos com aplicação de planejamento fatorial em dois níveis. O planejamento fatorial foi utilizado apenas na etapa das soldagens dos cordões isolados. As etapas subseqüentes foram confeccionar revestimentos planos com três passes de solda e revestimentos circunferenciais com três passes no interior do tubo, com esse girando e a tocha parada, onde foi avaliado principalmente o teor de Fe e resistência à corrosão. Para os cordões isolados na modalidade de corrente pulsada, foram obtidos valores de diluição de 3,6% a 22,26% e valores de R/L de 0,23 a 0,67, sendo o resultado mais satisfatório de 12,76% e 0,28 para D e R/L respectivamente. Para os corões isolados na modalidade de corrente convencional, os valores de diluição variaram de 9,62% a 23,19%, com R/L variando de 0,21 a 0,60, sendo o resultado mais satisfatório de 11,81% e 0,28 para D e R/L. Nos revestimentos com três passes foram alcançados melhores resultados de resistência à corrosão na modalidade de corrente convencional, sendo a variável distância do bico de contato à peça, DBCP, de maior influência nos resultados. / The need for exploration of heavier oils, in ever deeper wells and more aggressive environments has caused failures due to corrosion of materials with large economic and environmental losses. Therefore the aim of this study was to evaluate the influence of welding parameters on geometry (ratio of height to width - R/L), dilution (D), Iron content, % Fe, and hence corrosion resistance of Ni alloy overlays (Hastelloy-276) applied by welding on C-Mn steels. Submerged Arc welding process was used with pulsed and conventional current using nickel alloy wire electrode (Ni-Cr-Mo-4) with 1.14 mm diameter as filler metal. A segments of API 5L Gr B steel pipe with 18 mm thickness and 290 mm internal diameter was used as substrate. To relate the influence of the variables mentioned with the desired responses design of experiments technique with application of factorial design at two levels was used. The factorial design was used only in the stage of isolated welding beads. Subsequent steps consisted of overlay with 3 welding pass in plan position and inside of the pipe in rotation movement with the torch stopped. In this case it was also being evaluated mainly % Fe and corrosion resistance. For isolated beads in the pulsed current mode, dilution values were obtained from 3.6% to 22.26% and values of R / L from 0.23 to 0.67, being the most satisfactory result of 12.76% and 0.28 for D and R / L respectively. For isolated beads in the conventional current method,dilution values ranged from 9.62% to 23.19%, with R / L ranging from 0.21 to 0.60, being the most satisfactory result of 11.81% and 0.28 for D and R / L. At overlays with three passes, have been achieved better results in the corrosion resistance with conventional current mode, and the variable “distance from the contact tip to the workpiece, DBCP”, had the greatest influence on results.

Submitted by Johnny Rodrigues (johnnyrodrigues@ufcg.edu.br) on 2018-04-05T18:10:49Z No. of bitstreams: 1 ANDRÉ LOPES SOARES - DISSERTAÇÃO PPG-CEMat 2014..pdf: 6257060 bytes, checksum: 6c6fb12b0cbaaafb3788e358c240a5d5 (MD5) / Made available in DSpace on 2018-04-05T18:10:49Z (GMT). No. of bitstreams: 1 ANDRÉ LOPES SOARES - DISSERTAÇÃO PPG-CEMat 2014..pdf: 6257060 bytes, checksum: 6c6fb12b0cbaaafb3788e358c240a5d5 (MD5) Previous issue date: 2014-08-28 / Filmes finos de Nitreto de zircônio (ZrN) e nitreto da mistura titânio-zircônio (TiZrN) foram depositados sobre substratos de aço inoxidável 316L usando o método de RF Sputtering para deposição dos filmes. O planejamento de experimentos (DOE) tem sido reconhecido como um método poderoso para otimizar um processo complexo na indústria. Os efeitos do presente estudo foram verificar a viabilidade e confiabilidade da aplicação do método DOE em processos de RF Sputtering, otimizar os parâmetros de processamento para o processo de deposição, identificando os parâmetros sensíveis que afetam a espessura da camada depositada (E.C.D) e a resistência à corrosão (Ecorr.) Para o método de RF Sputtering, dois parâmetros, a taxa e tempo de deposição foram escolhidos para serem os parâmetros do processo. Depois da deposição, a estrutura de camada depositada foi caracterizada por Difração de Raios X (DRX) e por Microscopia Eletrônica de Varredura (MEV). Após o ensaio de polarização, a corrosão foi realizada a fim de investigar a relação entre o início da corrosão e a espessura da camada depositada. A análise de variância (ANOVA) foi realizada para avaliar os parâmetros sensíveis e prever as condições ideais. Com base na análise estatística, os parâmetros mais sensíveis no processo de RF Sputtering foram tanto a taxa como também o tempo de deposição do filme fino. As melhores condições de deposição foram a taxa de deposição máxima e tempo máximo. / Zirconium nitride (ZrN) and titanium-zirconium nitride (TiZrN) thin films were deposited on 316L stainless steel substrates using de RF Sputtering methods. Design of experiment (DOE) has long been recognized as a powerful method to optimize a complex process in industry. The purposes of present study were to verify the feasibility and reliability of the application of DOE method on de RF Sputtering processes and optimize the processing parameters for the deposition process, in which the sensitive parameters that affected the film properties were also identified. For de RF Sputtering method, two parameters, deposition rate and time were chosen to be the operating parameters. After deposition, the thin film structure was characterized by X-ray diffraction (XRD), and high-resolution scanning electron microscopy (SEM). After the polarization test, the corrosion analysis was carried out in order to investigate the relationship between the corrosion initiation and the thickness of the deposited layer. The analysis of variance (ANOVA) was conducted to assess the sensitive parameters and predict the optimum conditions. Based on the statistical analysis, the most sensitive parameters in de RF Sputtering process were both the deposition rate and time. The optimum deposition conditions in each system were maximum deposition rate and time.

Les pompes sèches primaires dédiées aux procédés de fabrication en microélectronique sont soumises à des environnements très corrosifs de plus en plus oxydants et halogénés (Cl2, F2 et O2). Or pour des raisons mécaniques et économiques, les parties fonctionnelles des pompes sont usinées dans la fonte à graphite sphéroïdale EN-GJS-500-7. La fonte est alors protégée par un dépôt de nickel-phosphore (NiP) chimique. Cette thèse, reprend des études classiques sur la cinétique et le mécanisme de nickelage d'une part, et sur l'optimisation des propriétés mécaniques et la résistance à la corrosion des couches de NiP d'autre part. Cependant, le caractère innovant de ce travail repose sur la réalisation de couches NiP sur un substrat en fonte à graphite sphéroïdale.L'étude de la cinétique de nickelage et la caractérisation morphologique des revêtements en fonction du temps de dépôt a montré l'influence de la nature chimique du substrat. Les sphères de graphite affleurantes à la surface du substrat n'étant pas catalyseur du nickel chimique, provoque des défauts dans le revêtement, dommageables pour la conformité du dépôt. Il a été montré qu'une polarisation cathodique de la surface du substrat pouvait, dans les premiers instants du dépôt, amorcer le nickelage à l'aplomb des sphères de graphite.Une relation entre la microstructure des dépôts en fonction des traitements thermiques subis et des propriétés mécaniques des couches de NiP a été mise une évidence. Les dépôts NiP amorphes présentent une faible dureté et un comportement ductile tandis que les dépôts cristallisés possèdent une dureté élevée et un comportement fragile. Ces dépôts ont une bonne tenue à la corrosion en milieux halogéné lorsqu'ils sont intacts. Actuellement, au niveau industriel, les dépôts les plus fragiles sont choisis, bien qu'ils présentent une résistance à la corrosion plus faible : en effet, la durée de vie des pompes est alors supérieure car les effets de grippage sont atténués.Mots-clés : nickel chimique, résistance à la corrosion, fonte à graphite sphéroïdale, caractérisation physico-chimique, couches minces, durabilité mécanique / Primary dry pumps dedicated to manufacturing processes in microelectronics are subjected to highly corrosive environments that are increasingly oxidizing and halogenous (Cl2, F2 and O2). However, for mechanical and economic reasons, the functional parts of the pumps are machined in EN-GJS-500-7 spheroidal graphite cast iron. The cast iron is consequently protected by a nickel-phosphorus chemical deposit. This thesis is based on classical studies on the kinetics and the nickel-plating mechanism on the one hand, and on the optimization of the mechanical properties and corrosion resistance of the NiP layers on the other hand. The innovative nature of this work is based on the production of NiP layers on a spheroidal graphite cast iron substrate.The study of the kinetics of nickel-plating as well as the morphological characterization of coatings as a function of the deposit time showed the influence of the chemical nature of the substrate. The flush graphite spheres on the surface of the substrate being not a catalyst for the chemical nickel, they can cause defects in the coating and a loss of compliance. It has been shown that a cathodic polarization of the surface of the substrate, in the first moments of the deposit, could initiate the nickel-plating right on the graphite spheres.A relationship exists between the microstructure of the deposits as a function of the thermal treatments undergone and the mechanical properties of the NiP layers. The amorphous NiP deposits have a low hardness and a ductile behavior while crystallized deposits have a high hardness and a brittle behavior. These deposits have a good resistance to corrosion in halogenated environments when they are intact. Actually, at the industrial level, the most brittle deposits are chosen, although they have a lower corrosion résistance: indeed, the service life of the pumps is higher because the seizing effect are minimized.Keywords: electroless nickel, resistance to corrosion, spheroidal graphite cast iron, physicochemical characterization, thin layers, mechanical durability