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ilustraciones, graficas En este trabajo se depositaron recubrimientos de TiAlVCuN sobre sustratos de acero inoxidable 316 L usando un sistema de cosputtering reactivo con fuentes HIPIMS y magnetrón. Como material de depósito se usó un blanco de titanio/aluminio y un blanco de vanadio/cobre. Los recubrimientos obtenidos fueron caracterizados química, microestructural y morfológicamente. La variación del voltaje de deposición en el blanco de V/Cu (con 5 niveles entre 510 V y 580 V), generó un cambio en la composición química representado principalmente en la variación de la cantidad de V, cambiando entre 3% y 12%. Estos recubrimientos exhibieron un crecimiento columnar, sin precipitaciones de Cu en la superficie. Además, se encontró una estructura cúbica tipo FCC, correspondiente con la formación de una solución sólida de TiAlVN sin presencia de Cu en estado metálico, por lo cual este probablemente podría estar disuelto en los bordes de grano de la matriz. Por otro lado, se evalúo la resistencia a la corrosión de los recubrimientos y el sustrato en dos tipos de electrolitos (Solución 3.5 wt. % de NaCl y Lactato de Ringer) a través de las técnicas de polarización potenciodinámica (TAFEL) y espectroscopia de impedancia electroquímica (EIS). El comportamiento frente a la corrosión mostrado por los recubrimientos fue similar al reportado para el sustrato. Sin embargo, el valor de la resistencia a la polarización disminuye con el aumento del voltaje de deposición. Lo anterior puede estar relacionado con un aumento en la cantidad de defectos presentes en el recubrimiento y la generación esfuerzos residuales que comprometen la adherencia de este al sustrato. (Texto tomado de la fuente) In this work TiAlVCuN coatings were deposited on 316 L stainless steel substrates using a reactive cosputtering system with magnetron and HIPIMS power sources. Titanium/aluminum and vanadium/copper blanks were used as deposit materials. The coatings obtained were chemically, microstructurally and morphologically characterized. The variation of the deposition voltage on the V/Cu target (with 5 levels between 510 V and 580 V), generated a change in the chemical composition represented mainly in the variation of the amount of V, changing between 3% and 12%. These coatings exhibited columnar growth, without Cu precipitation on the surface. In addition, an FCC-type cubic structure was found, corresponding to the formation of a TiAlVN solid solution without the presence of Cu in the metallic state, for which it could probably be dissolved at the grain boundaries of the matrix. On the other hand, coatings and substrate corrosion resistance was evaluated through the techniques of potentiodynamic polarization (TAFEL) and electrochemical impedance spectroscopy (EIS) using two types of electrolytes (3.5 wt. % NaCl NaCl solution and Ringer's Lactate). The corrosion behavior shown by the coatings was similar to that reported for the substrate. However, the polarization resistance value decreases with increasing deposition voltage. This could be related to an increase in the number of defects present in the coating and the generation of residual stresses that compromise its adherence to the substrate. Maestría Magíster en Ingeniería - Materiales y Procesos Ingeniería de superficies

Nickel–Iron coating was formed from a sulfate base electroplating bath under a current density of 3 A/dm 2 and turbulence of 300 rpm on a previously prepared cylindrical steel substrate. In order to obtain a sample including nickel composite coating, different amounts of alumina particle powder were added to the plating solution of the sample in question. By adding different quantities of ferrous sulfate to the electroplating bath under a current density of 2.5 A/dm 2 and turbulence of 300 rpm, an optimal sample containing 20 g/L of ferrous sulfate was obtained was free of any stress and microcracks. A hardness test was performed for the optimal sample among the nickel–iron¿ composite samples, and the sample containing 50 g/L of alumina particles was selected as the optimal sample. The Ni–Fe/Al 2O3 composite sample was tested for hardness, corrosion and wear. The obtained results showed that the highest hardness level is equivalent to 740 HV and the best corrosion resistance with the most positive corrosion potential. The lowest amount of wear mass is equal to 0.1 mg, and it showed the highest wear resistance.

ilstraciones, fotografías, graficas El titanio es un material altamente utilizado en la industria, condición ligada a sus buenas propiedades, sin duda alguna esto ofrece ventajas importantes con respecto a materiales como el acero; es así que las industrias de mayor demanda son la aeronáutica, medica, industria armamentista e incluso en el ámbito deportivo. En esta investigación se sintetizan recubrimientos metal-cerámica (60% wt de Ti+ 40% wt de TiB2) por la técnica de láser cladding coaxial sobre sustratos de Ti grado 2 y Ti-6Al-4V a diferentes niveles de energía (600, 900 y 1000 W) y se evalúa su comportamiento electroquímico en una solución de NaCl al 3.5% y a alta temperatura. Se caracteriza el material por microscopia electrónica de barrido, la evaluación electroquímica se hace por medio de espectroscopia de impedancia y polarización tafel, su estructura se evalúa por difracción de rayos X. La corrosión a alta temperatura es evaluada por medio de la técnica de oxidación cíclica. A nivel electroquímico los resultados muestran que los recubrimientos modifican la respuesta electroquímica del sistema, brindando protección sobre la superficie del material, lo cual está asociado a la formación de una capa protectora sobre la superficie del material (formación de compuestos de TiB, TiB2, TiO2; en la corrosión a alta temperatura se encuentra reducción de la degradación del material recubierto a diferencia del material sin recubrimiento, evidenciando la formación de compuestos principalmente constituidos por TiO2 (Texto tomado de la fuente). Titanium is a highly used material in the industry, a condition linked to its good properties, without a doubt this offers important advantages with respect to materials such as steel; Thus, the industries with the greatest demand are aeronautics, medicine, the arms industry and even sports. In this research, metal-ceramic coatings (60% wt Ti+ 40% wt TiB2) are synthesized using the coaxial laser cladding technique on Ti grade 2 and Ti-6Al-4V substrates at different energy levels (600, 900 and 1000 W) and its electrochemical behavior is evaluated in a 3.5% NaCl solution and at high temperature. The material is characterized by scanning electron microscopy, the electrochemical evaluation is done by means of impedance spectroscopy and tafel polarization, its structure is evaluated by X-ray diffraction. Corrosion at high temperature is evaluated using of the cyclic oxidation technique. At an electrochemical level, the results show that the coatings modify the electrochemical response of the system, providing protection on the surface of the material, which is associated with the formation of a protective layer on the surface of the material (formation of compounds of TiB, TiB2, TiO2; in high-temperature corrosion, a reduction in the degradation of the coated material is found, unlike the uncoated material, evidencing the formation of compounds mainly constituted by TiO2. Maestría Magíster en Ingeniería - Materiales y Procesos Ingenieria de superficies

Agradecimentos: A.R., A.G., P.P. contributed equally to this work. E.F.O. would like to thank the Brazilian agency FAPESP (grants 2016/18499-0 and 2019/07157-9) for financial support. Computational and financial support from the Center for Computational Engineering and Sciences at Unicamp through the FAPESP/CEPID grant no. 2013/08293-7 is also acknowledged. D.S.G. also acknowledges support from CAPES and CNPq. Some of the authors would like to thank the Board of Research in Nuclear Sciences (BRNS) (project no.: 57/14/05/2019-BRNS) for the financial support. C.S.T. was thankful for the support by AOARD grant no. FA2386-19-1-4039. CST acknowledges Ramanujan fellowship Abstract: Composites have played a key role in revolutionizing the automobile, marine, and aerospace industries. There is a constant attempt for the development of low-density composite materials with superior mechanical and corrosion-resistant properties for elevated temperature applications. Herein, an attempt is made to develop a nature-inspired unique aluminum-based composite with low-density polymer (polyethylene terephthalate, i.e., soft material) reinforcement, which shows an enhancement in strength and toughness. The composite is processed using the easily scalable and simple friction stir processing technique. Mechanical properties of the uniformly reinforced aluminum composite show double ultimate strength and fivefold improvement in plasticity. The ultimate strength of the composite increases at elevated temperatures. The experimental observations are further supported by theoretical calculations and molecular dynamics simulations FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPES CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQ Fechado

Orientador: Ambrósio Florêncio de Almeida Neto Tese (doutorado) ¿ Universidade Estadual de Campinas, Faculdade de Engenharia Química Resumo: Os revestimentos metálicos são muito utilizados em diversos objetos com finalidade decorativa ou de prevenção da corrosão. Com isso, as empresas de galvanoplastia contribuem sobremaneira com lançamentos de efluentes, nos recursos hídricos, com alta concentração de metais tóxicos. A precipitação química é uma prática convencional utilizada por essas empresas para o tratamento dos efluentes, porém tal método necessita de grandes quantidades de reagentes químicos, que ao final do processo geram lamas residuais, devendo ser dispostas em aterros especiais, transferindo desta forma o problema da fase líquida para a fase sólida. A proposta deste trabalho foi estudar a eletrodeposição como uma opção para o tratamento de um efluente contendo níquel iônico. Os ensaios de eletrodeposição foram realizados utilizando um efluente fornecido por uma empresa galvânica de joias constituída na sua forma original por sulfato de níquel, cloreto de níquel e ácido bórico. Além de remover íons de níquel do efluente o trabalho tem como objetivo obter ligas de Ni-W resistentes à corrosão. A concentração de níquel removido do efluente foi quantificada por espectroscopia ultravioleta-visível (UV- VIS) indicando remoção de 35,6 ± 12,3 %. Os padrões de Difração de Raios X (DRX) mostraram a cristalinidade dos depósitos, o microscópio eletrônico de varredura (MEV), acoplado à técnica de espectroscopia de energia dispersiva (EDS), determinou a homogeneidade e a composição com 76Ni /24W para a liga com melhor desempenho. Além disso, testes de resistência à corrosão (Rp) por polarização linear e impedância eletroquímica indicaram um valor de Rp de 29199 ohm.m2 Abstract: Metal coatings are widely used on various objects for decorative purposes or to prevent corrosion. As a result, electroplating companies contribute greatly to the discharge of effluents, in water resources, with a high concentration of toxic metals. Chemical precipitation is a conventional practice used by these companies for the treatment of effluents, however such method requires large amounts of chemical reagents, which at the end of the process generate residual sludge, and must be disposed of in special landfills, thus transferring the problem of liquid phase to the solid phase. The purpose of this work was to study electrodeposition as an option for the treatment of an effluent containing ionic nickel. The electrodeposition tests were performed using an effluent supplied by a galvanic jewelry company constituted in its original form by nickel sulfate, nickel chloride and boric acid. In addition to removing nickel ions from the effluent, the work aims to obtain corrosion resistant Ni-W alloys. The concentration of nickel removed from the effluent was quantified by ultraviolet-visible spectroscopy (UV-VIS) indicating removal of 35.6 ± 12.3%. The X-Ray Diffraction (XRD) patterns showed the crystallinity of the deposits, the scanning electron microscope (SEM), coupled with the energy dispersion X-ray spectroscopy (EDX) technique, determined the homogeneity and composition with 76Ni / 24W for the best performing alloy. In addition, corrosion resistance tests (Rp) by linear polarization and electrochemical impedance indicated a Rp value of 29199 ohm.m2 Doutorado Engenharia Química Doutora em Engenharia Química CAPES 33003017034-P8

The durability of metal-based constructions, especially those containing reinforced concrete, is mainly limited by corrosion processes. Diamond-like carbon (DLC)-coated silicon (Si) wafers provide a chemically inert and mechanically robust sensing interface for application in aggressive environments. In this study, iron-sensitive dyes, i.e., 2,3-dihydroxypyridine (DHP) and 1,2-dihydroxybenzol (DHB), were coated onto DLC-modified Si wafers for evaluating the potential of detecting corrosion processes via evanescent field absorption spectroscopy using Fourier-transform infrared spectroscopy. The obtained IR spectra reveal discernible changes of the dye layer after exposure to iron solutions, which indicates that indeed corrosion processes may be studied at molecular level detail., publishedVersion

Väitekirja elektrooniline versioon ei sisalda publikatsioone., Jay Mondali doktoritöös uuriti grafeenoksiidi ja redutseeritud grafeenoksiidi nanoliistakute valmistamise tehnoloogiat ja valmistati nende ainete baasil lihtkatted, hübriidkatted koos elektrit juhtiva polümeeri polüpürrooliga ning komposiitkatted koos metalloksiidide Al2O3 ja TiO2 nanokiledega. Katted kanti roostevaba terase või Ti-sulamist valmistatud katseobjektide pindadele, kasutades vurrkatmise, elektrokeemilise sadestamise ja aatomkihtsadestamise meetodeid. Katete omaduste uurimiseks kasutades laia hulka tahkisobjektide karakteriseerimise vahendeid, mis on saadaval TÜ Füüsika ja Keemia instituutides. Samuti määrati elektrokeemiliste mõõtmiste ja standarttestidega nende katete võime kaitsta alusmaterjale korrosiooni eest. Töö tulemusena näidati ära, et kuigi nii valmistatud liht- kui hübriidkatted aitavad teatud määral pidurdada korrosiooniprotsesse metallalustel, ei suuda need katted tõhusalt pidurdada punktkorrosiooni nimetatud aluste pikaajalisel hoidmisel tugevasti korrodeeruvates soolalahustes. Seevastu uudsed, submikromeetrilise paksusega grafeeni baasil loodud komposiitkatted näitasid üles väga head korrosioonikaitset mõlema sulami pinnal, ületades paljude tänapäeva tööstuses kasutatavate kümneid kuni sadu kordi paksemate kaitsekatete näitajaid. Töö tulemused on avaldatud eriala juhtivates ajakirjades ja tutvustatud rahvusvahelistel konverentsidel. Antud doktoritöö valmis prof. Väino Sammelselja juhendamisel. Tööd oponeerima on kutsutud prof. M. Ferreira Aveiro Ülikoolist ja dr. M. Krunks TTÜ-st., In this thesis corrosion inhibition performance of graphene and graphene oxide based composite/hybrid coatings was studied. Graphene is a two-dimensional one-atom-thick sheet of carbon having hexagonal lattice, and it is a basic structural unit of graphite. Graphene has proven to be one of the most popular advanced materials in recent developments. This carbon material is widely studied for advanced applications starting from energy harvesting to nanoelectronics and finishing with drug delivery because of many extraordinary properties of it. Among all of the properties the atom/ion barrier property was one of the most interesting for this work. Some studies to use graphene or graphene-based materials as a barrier sheet were published before starting this work and some appeared during the run of this investigation. Lately, the development of graphene and graphene oxide based functionalized biocompatible barrier coatings attracts a great attention among scientists and probably industrialists as well. But the use of graphene oxide/reduced graphene oxide nanoplatelets for corrosion protection of metal alloys was practically not studied before this work, despite the facts that the ideas of preparation the materials were known already decades, and as row material relatively cheap powder of natural graphite can be used. In this thesis the barrier properties of graphene/graphene oxide based nanostructured coatings, including composite and hybrid coatings were investigated towards corrosion protection. Investigations were carried through using different strategies: for the preparation of thin protective coatings spin-coating, electrochemical deposition and atomic layer deposition (ALD) techniques were used. For the corrosion inhibition performance studies of synthesized graphene oxide and reduced graphene oxide the hybrid coatings of graphene oxide-polypyrrole and the composite coatings of graphene-metal oxide laminates were prepared. The extent of protection ability of the coatings deposited onto AISI type 304 stainless steel and Ti-6Al-4V alloy substrates was studied thoroughly by electrochemical methods, as open circuit potential and Tafel plots, voltammetry and electrochemical impedance spectrometry, and tested by standard ASTM G48 A and long-time immersion tests in salt solutions. The studies revealed that prepared graphene and graphene oxide based hybrid and especially composite coatings well inhibit corrosion of the metal substrates. This definitely increases lifetime and stability of the metal details and equipment made from these materials, helping to preserve the materials and energy, thus helping to develop also a more sustainable society.

Orientador: Ambrósio Florêncio de Almeida Neto Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química Resumo: O processo de corrosão está constantemente transformando os materiais metálicos de modo que em alguns casos a durabilidade e o desempenho dos mesmos ficam comprometidos. Uma forma de minimizar os efeitos da corrosão em materiais metálicos é revesti-los com outros materiais. A eletrodeposição é um método muito utilizado na obtenção de revestimentos metálicos resistentes à corrosão. Esse método também pode ser utilizado como técnica de tratamento de efluentes contaminados com metais tóxicos. A eletrodeposição promove a reação de redução de íons, presentes em soluções, em sua espécie metálica, a qual se deposita em um eletrodo, recuperando os metais, e em muitos casos possibilitando a reutilização da água. Este trabalho visa à obtenção de ligas metálicas de tungstênio e apresenta um apelo ambiental referente à recuperação de metais tóxicos de efluentes, que podem ser utilizados como metais indutores na formação das ligas de tungstênio. Os depósitos binários estudados foram Fe-W, Ni-W e Co-W, sendo estes considerados como uma codeposição do tipo induzida, pois a eletrodeposição do tungstênio a partir dos seus sais dissolvidos em solução aquosa não é possível. A otimização do processo de eletrodeposição das ligas de tungstênio com o ferro, o cobalto e o níquel, foi desenvolvida por meio de um estudo sobre a influência dos parâmetros de operação (concentração do sal fonte do metal, temperatura do banho e densidade de corrente) na eficiência de deposição e na resistência à corrosão. Para o estudo do processo de eletrodeposição foi realizado um planejamento fatorial 23 para cada liga metálica. As ligas binárias Fe-W, Ni-W e Co-W foram eletrodepositadas sobre um substrato de cobre com área superficial de oito cm2 e caracterizadas quanto a morfologia e composição química. As ligas obtidas que apresentaram boa aderência foram analisadas por meio das curvas de polarização e diagramas de impedância eletroquímica como forma de avaliar os revestimentos em relação à resistência à corrosão Abstract: The corrosion process is constantly changing the metal material in a way that its durability and performance are compromised. One way to minimize the effects of corrosion in metallic materials is coating them with other materials. Electroplating is a widely used method to obtain metal coatings that are resistant to corrosion. This method can also be used as a treatment technique for the wastewater which is contaminated with toxic metals. The electrodeposition ions promote the reduction reaction, present in solution, in its metallic state, which is deposited on an electrode, therefore recovering metals, and in many cases allowing the reuse of water. This study aims at developing and obtaining alloys of tungsten and presents an environmental call related to the recovery of toxic metals from effluent that can be used to induce the formation of metal tungsten alloys. The binary deposits studied were Fe-W, Ni-Co-W and W, being these considered as a codeposition of induced type because tungsten electrodeposition from salts dissolved in the aqueous solution is not possible. The optimization of the electrodeposition process of the tungsten alloys with iron, cobalt and nickel, has been developed through a study on the influence of the operating parameters (concentration of the source of the metal salt, bath temperature and current density) the deposition efficiency and corrosion resistance. For the study of the electrodeposition process a 23 factorial planning was conducted for each metallic alloy. The binary Fe-W, Ni-Co-W and W were electrodeposited on a copper substrate with a surface area of eight cm2 and characterized according to its morphology and chemical composition. The alloys obtained with good grip were analyzed using linear potentiodynamic polarization curves and electrochemical impedance diagrams for to evaluate the coatings for resistance to corrosion Mestrado Engenharia Química Mestra em Engenharia Química FAEPEX FAPESP

In electrical contacts, thin films of nickel and gold or silver are traditionally plated on top of a copper base plate to provide corrosion resistance and wear protection. Most recently, the rising cost of noble metals and intensified competition in manufacturing technology has driven the industry towards thinner plating layers, which gives rise to questions regarding how interfacial contact and wear is affected by plating thickness and material characteristics. This study uses a combination of finite element analysis and ex-situ wear measurement to determine the effect of gold plating thickness on wear performance under linear reciprocating sliding contact. Correlations between predicted and measured results lead to insight into the stress state within the multi-layer system under contact conditions as well as a wear map for gold platings that can be used to inform future connector designs. The middle layer material, Ni, is relatedly inexpensive, but takes a relatively long time to deposit. Because this deposition time has a direct influence on the cost of manufacturing, it is important to reduce the Ni thickness as well. This project thus determines how different combinations of Ni and Au properties influence wear and subsurface layer exposure, which is critical for determining the makeup of future, low-cost, connector designs.

fotografías a blanco y negro, fotografías a color, gráficas, ilustraciones, tablas En esta investigación se evaluó la resistencia a la erosión, corrosión y erosión-corrosión de los aceros AISI D2 y AISI H13 sin recubrir y con recubrimientos binarios de NbC, VC y ternarios de VxNbyCz, producidos a través de la técnica de deposición por difusión termorreactiva (TRD). Los tratamientos TRD se llevaron a cabo en una mezcla de sales fundida que consta de bórax, ferroaleación: ferro-niobio, ferro-vanadio (Fe-Nb, Fe-V) y aluminio a una temperatura de 1293 K durante 4 horas, usando un horno de calentamiento por resistencia. La estructura cristalográfica de los recubrimientos se evaluó mediante difracción de rayos X (XRD), la morfología se observó mediante microscopia electrónica de barrido (SEM),microscopia óptica de sección trasversal y microscopia de escaneo láser confocal (CLSM). El comportamiento frente a la erosión corrosión de los recubrimientos fue estudiado usando el procedimiento indicado en la norma ASTM G119-09, mediante una celda de impacto tipo Jet para ángulos de impacto de 30 y 90 ° con velocidades de flujo de 11,5 m/s y 9,5 m/s. El efecto erosivo se obtuvo mediante la acción de un chorro de agua con partículas de SiO2 entre 200 y 300μm de tamaño, el efecto corrosivo se obtuvo mediante la acción del chorro con una solución electrolítica de 3,5% NaCl, el efecto sinérgico de erosión-corrosión se estudió a través de la acción del chorro de agua al 3,5% de NaCl con el 10% en peso de partículas de SiO2. Los patrones de difracción de rayos X mostraron que la capa ternaria (VNbC2) se orientó preferentemente a lo largo de la dirección [200] con una estructura cúbica centrada en la cara (FCC).La microscopía óptica mostró que los recubrimientos crecieron de manera homogénea con un espesor regular. Los estudios de erosión-corrosión indicaron una fuerte reducción en el efecto sinérgico sobre el recubrimiento para ambos aceros frente a los aceros sin recubrir. El efecto erosivo hizo la mayor contribución para los recubrimientos de carburo de niobio (NbC). La velocidad de pérdida total de material por E/C para el acero sin recubrir y los recubrimientos fue superior al efecto de erosión pura. (Texto tomado de la fuente) In this research the erosion, corrosion and corrosion-erosion behavior of AISI D2 and AISI H13 steel for the bare steel and in addition with binary VC and NbC coatings and ternary VNbC2 coatings, produced by the Thermoreactive Deposition/Diffusion Process (TRD) was evaluated. The TRD treatments were carried out by mixture of molten salts, consisting of borax, ferroalloy: Ferro-niobium, Ferro-vanadium (Fe-Nb, Fe-V) and aluminum at 1293 °K for 4 hours, using a resistance-heating furnace. The crystallographic structure of the coatings was evaluated using X-ray diffraction (XRD), the morphology was observed by scanning electron microscopy (SEM), light microscopy of cross-section and confocal laser scanning microscopy (CLSM). The erosion-corrosion behavior of the coatings was studied following the procedure described by ASTM G119-09 standard by a jet impingement cell type for impact angles of 30 and 90 ° with speeds of 11,5 m/s and 9,5 m/s. The erosive effect was obtained by action of a water jet with SiO2 particles between 200 and 300μm in size. The corrosive effect was obtained by the action of the jet with an electrolyte solution of 3.5% NaCl. The synergistic effect of erosion-corrosion was studied by the water jet action with an electrolyte solution to 3.5% NaCl and 10% by weight of SiO2 particles. The patterns of X-ray diffraction showed that the ternary coatings (VNbC2) was preferentially oriented along the direction [200] with a Face Centered Cubic structure (FCC).The optical microscopy showed that the coatings uniformly grew with a regular thickness. The erosion-corrosion studies indicated a strong reduction in the synergistic effect on the coating for both steels versus bare steels. The erosive effect made the largest contribution to NbC coatings. The total loss rate of material by E/C for bare steel and coatings was superior to the effect of pure erosion Universidad Nacional de Colombia sede Bogotá Maestría Magíster en Ingeniería - Materiales y Procesos Ingeniería de Superficies Ingeniería de fabricación y materiales

Se caracterizaron propiedades mecánicas, morfológicas y tribológicas, del acero AISI 316 del cual se fabrican los impulsores de las bombas Wemco. El análisis se realizó al material en estado de suministro y con recubrimiento de carburos de tungsteno depositado por medio del proceso eutalloy el cual se llevó a cabo en la empresa Sager S.A. Una vez realizada la deposición del recubrimiento, se procedió a realizar los ensayos de erosión-corrosión y corrosión. Se realizaron ensayos de erosión-corrosión en un equipo patentado por la Universidad Autónoma, con ángulos de impacto de 30, 45 y 90º y tiempos de proceso de 3 y de 2 horas por probeta en una solución ½ M H2SO4 + 3.5%NaCl + 30% de peso en Sílice. También se realizaron pruebas de erosión corrosión dinámica en un equipo Erosión-Corrosión de la universidad Militar de Colombia. Las probetas se impactaron a ángulo de 90° a 23 horas de proceso, al comparar los resultados, el comportamiento de la resistencia a la erosión-corrosión fue similar. El Acero en estado de suministro debido a los impactos recibidos presentó alta deformación plástica por lo tanto presento menor pérdida de masa lo que implica una mayor resistencia al desgaste erosivo-corrosivo, mientras que las probetas con recubrimiento presentaron mayor pérdida de masa en la primera hora del análisis y a partir de este momento tuvo un comportamiento similar al del acero sin recubrimiento. Para la caracterización de la respuesta corrosiva se usó la técnica con curvas de polarización dinámicas Tafel, la caracterización microestructural mediante microscopia electrónica de barrido (MEB) y microscopia óptica. El estudio mostró que es favorable aplicar el recubrimiento de carburos de tungsteno en los impulsores de las bombas Wemco del Ingenio Manuelita porque permitirá conservar más tiempo la geometría de diseño del álabe y esto a su vez, aumentará su vida útil Pasantía de Investigación (Ingeniero Mecánico)-- Universidad Autónoma de Occidente, 2012 Pregrado Ingeniero(a) Mecánico(a)

Se obtuvieron aleaciones austeníticas del sistema Fe-Mn-Al, en el intervalo Fe-(4,9~11,0 wt% de Al)-(17,49~34,3 wt% de Mn)-(0,43~1,25 wt% de C), las cuales fueron fundidas en un horno de inducción a partir de materiales de alta pureza. Las aleaciones se evaluaron con respecto a fenómenos de corrosión, erosión en medio húmedo y corrosión-erosión, a un ángulo de impacto de 90º. Para la evaluación de la corrosión se empleó una solución compuesta por 0,5 M de NaCl y partículas de sílice con tamaño entre 210 y 300 µm, con el fin de analizar el efecto del contenido de manganeso y aluminio en la resistencia a la erosión y a la corrosión-erosión de estas aleaciones. Para la caracterización de la respuesta corrosiva se usó la técnica con curvas de polarización potenciodin ámicas y la extrapolación de Tafel, la caracterización microestructural mediante microscopia electrónica de barrido (MEB) y los productos de corrosión a través de difracción de rayos X (DRX). We obtained austenitic alloys of the Fe-Mn-Al, Fe in the range (4.9~11.0 wt% Al) - (17.49~34.3 wt% Mn) -(0, 43 ~ 1.25 wt% C), which were melted in an induction furnace from high purity materials. The alloys were evaluated with respect to corrosion, wet erosion and corrosion-erosion at an impact angle of 90°. For the evaluation of corrosion a solution composed of 0.5 M NaCl and silica particles with size between 210 to 300 microns was used in order to analyze the effect of aluminum and manganese content in the resistance to erosion and corrosion-erosion of these alloys. To characterize the corrosion, response technique was used by potentiodynamic polarization curves and using the same technique as Tafel extrapolation, the microstructural characterization by scanning electron microscopy (SEM), and the composition of corrosion products were analyzed using diffraction of X-rays (XRD).

En este artículo se presenta el estudio de las propiedades electroquímicas de las películas anódicas porosas, crecidas sobre la aleación de aluminio AA 2024-T3, obtenidas con la técnica de corriente directa (DC) con densidades de corriente de 10, 15 y 20 mA/cm2 en una solución de H2SO4. El análisis morfológico se realizó con microscopia de fuerza atómica (AFM) y permitió identificar que el aumento en la densidad de corriente genera mayor homogeneidad de la superficie y disminución en los valores de rugosidad. Con la medida de microdureza Vickers, se determinó que los anodizados mejoran su resistencia mecánica frente al sustrato. Para evaluar la resistencia a la corrosión se utilizaron la técnica de espectroscopia de impedancia electroquímica (EIS) y las curvas de polarización Tafel. A partir de estas técnicas se determinó que el aumento en la densidad de corriente forma películas que incrementan la resistencia a la corrosión. Adicionalmente se modeló el comportamiento electroquímico de las películas producidas y se hizo la correlación con las imágenes obtenidas por microscopia electrónica de barrido (SEM). This paper reports the results of a study about the corrosion electrochemical properties of the porous anodic films grown on aluminium alloys 2024 T3, obtained by DC technique at current densities of 10, 15 and 20 mA/cm2 in an aqueous solution of H2SO4. Materials characterization was carried out using atomic force microscopy (AFM) allowing identify that the increase in the current density produces a greater surface homogeneity and a decrease of average surface roughness. The micro-hardness Vickers measurements determined that the hard anodization layer improves their mechanical resistance related to the substrate. To evaluate the corrosion resistance of the anodic films, the EIS technique and Tafel polarization curves were employed. From these techniques it has been determined that the increase in the current density values forms films that increase the corrosion resistance. In addition the electrochemical behavior of the obtained films was modeled and the correlation with the images obtained by scattering electron microscopy (SEM) was made.

Orientadores: Amauri Garcia, Wislei Riuper Osorio Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica Resumo: Produtores de baterias chumbo-ácido têm modificado os processos de produção e composição química das ligas utilizadas nas grades das baterias com intuito de diminuir o seu peso final, bem como reduzir os custos de produção e também aumentar o ciclo de vida útil e a resistência à corrosão. As morfologias das estruturas de solidificação, caracterizadas principalmente por arranjos celulares e dendríticos, e suas grandezas representadas por espaçamentos celulares e dendríticos controlam a distribuição de soluto, segundas fases dentro das regiões intercelulares ou interdendríticas, que determinam as propriedades finais. O comportamento mecânico e as características estruturais dos componentes de bateria têm papel importante no desempenho das baterias. O presente trabalho pretende contribuir para o entendimento do desenvolvimento microestrutural de ligas diluídas do sistema Pb-Sn (Pb-1,0%Sn e Pb-2,5%Sn) que possuem elevada importância para a indústria na fabricação de componentes de baterias automotivas e estacionárias. Os experimentos de solidificação realizados em dispositivo no qual o calor é extraído somente pelo sistema de resfriamento a água, localizado na base do conjunto lingote/lingoteira (solidificação ascendente). As variáveis térmicas de solidificação foram determinadas a partir do registro de temperaturas de termopares posicionados dentro da lingoteira em diferentes posições em relação à superfície refrigerada do lingote. Amostras das mencionadas ligas Pb-Sn foram utilizadas para analisar as influências das variáveis térmicas de solidificação e da concentração de soluto nas macro e microestruturas resultantes e na resistência mecânica. Foram determinados os limites de resistência à tração e alongamentos específicos em função do espaçamento celular e a influência da microestrutura no comportamento eletroquímico foi avaliada por intermédios dos ensaios de espectroscopia de impedância eletroquímica, extrapolação de Tafel, curvas de polarização e análise por circuito equivalente em solução eletrolítica de ácido sulfúrico. Observou-se que a resistência a corrosão diminui e o limite de resistência a tração aumenta com a diminuição do espaçamento celular. Abstract: Lead-acid batteries manufacturers have modified the manufacturing processes and the chemical composition of alloys used in battery grids in order to decrease their weight as well as to reduce the production costs, and to increase the battery life-time cycle and the corrosion-resistance. The morphological microstructures characterized by cellular and dendritic arrays and its correspondents cellular and dendrite arm spacings control the solute distribution, second phases in the intercellular and interdendritic regions affecting the resulting properties. The mechanical behavior and microstructural characteristics of lead-acid battery components have an important role in the battery performance. The present work aims to contribute to the understanding of the microstructural development of dilute Pb-1,0 wt.%Sn and Pb-2.5 wt.%Sn alloys which are widely applied in the manufacturing of automobile and stationary lead-acid batteries. A water-cooled vertical upward unidirectional solidification system was used to obtain the samples. The experimental set-up was designed in such a way that the heat was extracted only through the water-cooled bottom, promoting upward directional solidification. Thermal readings were obtained by thermocouples positioned at different distances from the heat-extracting surface at the casting bottom. Pb-Sn alloy samples were used to analyze the effects of the thermal solidification variables and solute content on the resulting macro and microstructures and on the mechanical properties. The ultimate tensile strength and the elongation were determined as a function of the cellular arm spacing. The effect of the resulting microstructure on the electrochemical corrosion behavior was also analyzed based on electrochemical parameters, determined by Tafel plots, polarization curves and an equivalent circuit analysis after corrosion tests carried out in a sulphuric acid solution. It was observed that the corrosion resistance decreases and the ultimate tensile strength increases with decreasing cellular spacing. Mestrado Materiais e Processos de Fabricação Mestre em Engenharia Mecânica

La biocompatibilidad de los metales utilizados en implantología está íntimamente relacionada con las características superficiales de los implantes tanto desde un punto de vista químico como topográfico. El objetivo de este trabajo es aplicar varios tratamientos superficiales al acero inoxidable 316 L y caracterizar, posteriormente, la superficie físico-químicamente. La superficie pulida de varios discos de acero 316 L fue tratada mediante los procesos de: granallado, variando el tamaño y la naturaleza de la partículas proyectadas, y anodizado electroquímico. Con el fin de caracterizar las superficies obtenidas con cada tratamiento se observó la morfología superficial mediante Microscopia Electrónica de Barrido e Inteferometría Óptica y se evaluó el efecto de dichos tratamientos en la resistencia a la corrosión y en la liberación de iones níquel y cromo mediante ensayos in vitro. Los resultados revelaron que el tratamiento de granallado permite obtener un amplio rango de rugosidades incrementando el área real hasta un 54% pero disminuyendo ligeramente la resistencia a la corrosión del material. El proceso de anodizado prácticamente no tuvo efectos en la topografía sin embargo redujo considerablemente la resistencia a la corrosión del metal. Todos los tratamientos estudiados disminuyeron ligeramente la liberación de iones cromo y níquel.

Aluminium smelting is a high temperature electrometallurgical process, which suffers considerable inefficiencies in power utilization and equipment maintenance. Aluminium smelting cell works in the extreme environments that contain extraordinarily aggressive gases, such as HF, CO and SO2. Mild steel used as a structural material in the aluminium industry, can be catastrophically corroded or oxidized in these conditions. This project was mainly concerned with extending the lifetime of metal structures installed immediately above the aluminium smelting cells. An aluminium-rich coating was developed on low carbon steel A06 using pack cementation technique. Yttria (Y2O3) was also used to improve the corrosion resistance of coating. Kinetics of the coating formation were studied. XRD, FESEM and FIB were employed to investigate the phase constitution and the surface morphology. Together with other potentially competitive materials, aluminium-rich coating was evaluated in simulated plant environments. Results from the long time (up to 2500h) isothermal oxidation of materials at high temperature (800ºC) in air showed that the oxidation resistance of coated A06 is close to that of stainless steel 304 and even better than SS304 in cyclic oxidation tests. Coated A06 was also found to have the best sulfidation resistance among the materials tested in the gas mixture contains SO2 at 800ºC. Related kinetics and mechanisms were also studied. The superior corrosion resistance of the coated A06 is attributed to the slow growing alpha-Al2O3 formed. Low temperature corrosion tests were undertaken in the gas mixtures containing air, H2O, HCl and SO2 at 400ºC. Together with SS304 and 253MA, coated A06 showed excellent corrosion resistance in all the conditions. The ranking of the top three materials for corrosion resistance is: 253MA, coated A06 and SS304. It is believed that aluminised A06 is an ideal and economical replacement material in the severe corrosive aluminium smelting cell environment.

The corrosion resistance of two commercially available SiC filter materials coated with Mg-doped Al₂ TiO₅ and (Ca 0.6.6' Mg0.52) Zr₄P₆O₂₄ (CMZP) was investigated in high-temperature high pressure (HTHP) alkali-steam environments. Coated specimen properties, including cold and hot compressive strengths, bulk density, apparent porosity, permeability, and weight change, detected after exposure to 92% air-S% steam 10 ppm Na at 8OO°C and 1.8 MPs for 500 h were compared with those of uncoated specimens. Procedures for applying homogeneous coatings of Mg-doped Al₂ TiO₅ and CMZP to porous SiC filters were established and coating of the materials was successfully accomplished. Efforts to stabilize the Al₂ TiO₅ coating composition at elevated temperature were successful. Coatings show promise for providing improved corrosion resistance of the materials in pressurized fluidized bed combustion (PFBC) environments as evidenced by higher compressive strengths exhibited by coated SiC specimens than by uncoated SiC specimens following HTHP alkali-steam exposure. Master of Science

The corrosion resistance of chemically modified β-eucryptite (Li0.41Mg0.035AlP0.52Si0.480₄) having low expansion anisotropy and a near zero coefficient of thennal expansion was evaluated. Samples were exposed to aqueous hydrochloride acid at temperatures up to 100°C and environments containing sodium sulfate up to l000°C. The corrosion resistance was characterized by dilatometry, scanning electron microscopy, X-ray diffraction, energy dispersive x-ray analysis, weight variations, and mechanical properties variations. The results show that modified β-eucryptite is more severely corroded than commercial lithium-alumina-silicate glass-ceramics when exposed to these environments. Aqueous HCI removes AIP04 from modified β-eucryptite leaving a very porous structure. Molten salt corrodes modified β-eucryptite by penetration of sodium and sulfur which form an alkali melt under the surface. The modulus of rupture and the Young's modulus are reduced by both types of corrosion. Master of Science