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In-Situ TiC-Fe Deposition on Mild Steel Using a Laser Cladding ProcessEmamian, Ali 26 July 2011 (has links)
The growing interest in increasing the wear resistance and hardness of surfaces that are in contact with abrasives or corrosive materials has inspired the development of several processes for creating protective coatings. In-situ laser cladding is one of the most promising of these processes. It enables the formation of a uniform coating by melting powder to form the desired composition from a pure powder component.
In this research, pure Ti, graphite, and Fe are used for in-situ laser cladding on a steel substrate to form an Fe-TiC metal matrix composite (MMC). The effect of laser parameters on both the quality of the bonding and morphology of the in-situ-formed TiC iron-based composite clad are investigated. Results show that laser parameters play a crucial role in determining the clad quality and clad microstructure. Two combined parameters, effective energy and powder deposition density, are used to study the effect of laser parameters (i.e., laser power, scan speed and powder feed rate) on the clad properties. While results indicate that combined parameters help to determine the quality limit, laser process parameters need to be taken into account in order to study the clad microstructure.
To increase the clad hardness and TiC volume fraction, C:Ti atomic ratio should increase from 45:55 to 55:45, and Fe percentages in the powder composition should decrease from 70 wt% to the 10 wt%. By varying the powder composition, a change in TiC morphology, clad microstructure and clad hardness occurs. The dilution effect is also considered in the interpretation of results.
In order to estimate wear resistance, the ASTM G65-A procedure was selected to perform tests on various clad compositions. An increased wear resistance is seen when the volume fraction of TiC is increased.
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1.3£gm quantum dot-in-a-well laserLin, Ting-Yu 14 July 2011 (has links)
The purpose of this thesis is to fabricate 12-layer In0.75Ga0.25As quantum dot-in-a-well (In0.1Ga0.9As) structures grown by molecular-beam epitaxy (MBE) on GaAs substrate, and analyze the optical properties of laser devices for optical fiber communication systems.
For the laser structures, larger Al content AlGaAs cladding layer enhance the optical confinement, but encounter much challenges to improve the quality. After we simulate and fabricate different Al content laser structures, we find the best cladding layer composition - Al0.2Ga0.8As which performs a best material gain. In the active layer, 12 layers In0.75Ga0.25As quantum dots (QDs) and QDs in a well (DWell) structure, and DWell with Be-doping in the well structure are included in this study. The well structure slows down the hot carriers speed and Be-doping decrease the carrier life time and increases the electron-hole pair recombination rate. We increase the QDs deposition coverage to move the emission wavelength to 1.3£gm, but the high temperature cladding layer growth process indirectly anneal the QDs and result in the emission wavelength blue shift to 1.24£gm.
In the laser fabrication, to transport the light wave in smaller dispersion loss single mode waveguide, wet etching photolithography processes are adapted in this study to fabricate 2£gm width ridge waveguide. The as-cleaved facets are used as Fabry-Perot laser mirrors in ridge waveguide lasers.
Finally, the current density of QD Laser(C528) lasing in CW mode is 581A/cm2, slope efficiency of 510mW/A and maximum power/facet of 65mW are obtained.Then the current density of DWELL+PD Laser(C540) lasing in CW mode is 880A/cm2, slope efficiency of 430mW/A and maximum power/facet of 34mW are obtained.
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Influence of nonstructural cladding on dynamic properties and performance of highrise buildingsPalsson, Hafsteinn 12 1900 (has links)
No description available.
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Three dimensional nonlinear dynamic response of an RC structure with advanced claddingEl-Gazairly, Loai F. 05 1900 (has links)
No description available.
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In-Situ TiC-Fe Deposition on Mild Steel Using a Laser Cladding ProcessEmamian, Ali 26 July 2011 (has links)
The growing interest in increasing the wear resistance and hardness of surfaces that are in contact with abrasives or corrosive materials has inspired the development of several processes for creating protective coatings. In-situ laser cladding is one of the most promising of these processes. It enables the formation of a uniform coating by melting powder to form the desired composition from a pure powder component.
In this research, pure Ti, graphite, and Fe are used for in-situ laser cladding on a steel substrate to form an Fe-TiC metal matrix composite (MMC). The effect of laser parameters on both the quality of the bonding and morphology of the in-situ-formed TiC iron-based composite clad are investigated. Results show that laser parameters play a crucial role in determining the clad quality and clad microstructure. Two combined parameters, effective energy and powder deposition density, are used to study the effect of laser parameters (i.e., laser power, scan speed and powder feed rate) on the clad properties. While results indicate that combined parameters help to determine the quality limit, laser process parameters need to be taken into account in order to study the clad microstructure.
To increase the clad hardness and TiC volume fraction, C:Ti atomic ratio should increase from 45:55 to 55:45, and Fe percentages in the powder composition should decrease from 70 wt% to the 10 wt%. By varying the powder composition, a change in TiC morphology, clad microstructure and clad hardness occurs. The dilution effect is also considered in the interpretation of results.
In order to estimate wear resistance, the ASTM G65-A procedure was selected to perform tests on various clad compositions. An increased wear resistance is seen when the volume fraction of TiC is increased.
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Stiffening effect of cladding on light-weight structures /Lawrence, S. J. January 1972 (has links) (PDF)
Thesis (M.Eng.Sc.)--University of Adelaide, Dept. of Civil Engineering, 1974. / "January 1972." Includes bibliographical references.
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Desenvolvimento de processos de reciclagem de cavacos de Zircaloy via refusão em forno elétrico a arco e metalurgia do pó / Development of processes for zircaloy chips recycling by electric arc furnace remelting and powder metallurgyPEREIRA, LUIZ A.T. 21 January 2015 (has links)
Submitted by Claudinei Pracidelli (cpracide@ipen.br) on 2015-01-21T10:18:45Z
No. of bitstreams: 0 / Made available in DSpace on 2015-01-21T10:18:45Z (GMT). No. of bitstreams: 0 / Tese (Doutorado em Tecnologia Nuclear) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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Laser cladding surface treatment for enhancement of mechanical propertiesYang, Wen Fu January 2003 (has links)
Thesis (MTech (Mechanical Engineering))--Peninsula Technikon, 2003 / Systematic laser cladding experiments were performed using a mixture of a Nickel
base alloy powder mixed with tungsten carbide powder (percentage contents of
tungsten carbide from 10% to 40%) on EN8 steel substrate with pre-placed powder
method. Laser cladding of the Nickel base alloy powder + 50% tungsten carbide
powder on EN9 steel substrate was performed with powder injection method as well.
A Finite Element Method for calculating the surface temperature distribution was
used to help prediction of temperature distribution laser cladding results. Composition
of cladding materials was designed; a sticking agent was chosen for the pre-placed
powder method. Clad coatings were obtained for different process parameters for
laser cladding, and a detailed study of the affects of these parameters has been carried
out.
The characteristic microstructure and properties of the clad layers and interface were
investigated by using an optical microscope, a micro hardness tester and a makeshift
wear test. A comprehensive review is presented on the dilution of the coating and the
typical problems experienced with the coating substrate interface.
The results show that microstructure of clad layers comprise three zones: the cladding
layer, bonding zone and heat-affected zone. The results showed that tungsten carbide
particles increased the hardness and wear resistance as expected. Wear resistance of
laser cladding coating is 3.5 times than that of substrate. The micro hardness range of
the cladding layer is from RV 981.5 to RV 1187, which is 2-3 times than that of
substrate. The micro hardness varies from cladding coating to transition layer then to
heat affected zone and substrate along a gradient.
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Desenvolvimento de processos de reciclagem de cavacos de Zircaloy via refusão em forno elétrico a arco e metalurgia do pó / Development of processes for zircaloy chips recycling by electric arc furnace remelting and powder metallurgyPEREIRA, LUIZ A.T. 21 January 2015 (has links)
Submitted by Claudinei Pracidelli (cpracide@ipen.br) on 2015-01-21T10:18:45Z
No. of bitstreams: 0 / Made available in DSpace on 2015-01-21T10:18:45Z (GMT). No. of bitstreams: 0 / Reatores PWR empregam, como combustível nuclear, pastilhas de UO2 acondicionadas em tubos de ligas de zircônio, chamados de encamisamento. Na sua fabricação são gerados cavacos de usinagem que não podem ser descartados, pois a reciclagem deste material é estratégica quanto aos aspectos de tecnologia nuclear, econômicos e ambientais. As ligas nucleares têm altíssimo custo e não são produzidas no Brasil, sendo importadas para a fabricação do combustível nuclear. Neste trabalho são abordados dois métodos para reciclar os cavacos de Zircaloy. No primeiro, os cavacos foram fundidos utilizando um forno elétrico a arco para obter lingotes. O segundo usa a técnica da metalurgia do pó, onde os cavacos foram submetidos à hidretação e o pó resultante foi moído e isostaticamente prensado e, a seguir, sinterizado a vácuo. A composição química, as fases presentes e a dureza no material foram determinadas. Os lingotes foram tratados termicamente e laminados, sendo que as microestruturas foram caracterizadas por microscopia óptica e eletrônica de varredura. Os resultados para ambos os métodos mostraram que a composição do Zircaloy reciclado cumpre as especificações químicas e apresentaram microestrutura adequada para uso nuclear. Os bons resultados do método de metalurgia do pó sugerem a possibilidade de produzir pequenas peças, como as tampas do encamisamento - end-caps, usando a sinterização no formato quase final (near net shape). / Tese (Doutorado em Tecnologia Nuclear) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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ANÁLISIS MICROESTRUCTURAL DE RECUBRIMIENTOS COMPUESTOS DE CARBURO DE TITANIO Y MATRIZ DE TITANIO DEPOSITADOS POR LÁSERCandel Bou, Juan José 09 March 2012 (has links)
Las aleaciones de titanio poseen una excelente resistencia mecánica específica combinada con una gran resistencia a la corrosión y oxidación. No obstante, su comportamiento frente al desgaste es pobre y limita su uso en muchas aplicaciones para la industrial naval, aeronáutica y petroquímica.
En este trabajo se propone utilizar el recubrimiento por laser o "laser cladding" para depositar capas de material compuesto de matriz de Ti6Al4V reforzado con diferentes contenidos en peso de partículas cerámicas duras de carburo de titanio (TiC) con el fin de mejorar el comportamiento frente al desgaste.
Se trata de un trabajo experimental complejo ya que el titanio posee una enorme reactividad con la atmosfera que dificulta enormemente su procesado por láser. Por este motivo, se ha diseñado una tabla de experimentación que permite estudiar el procesado por laser en varias etapas de complejidad creciente para analizar el efecto de las variables por separado.
La experimentación de ha dividido en cuatro etapas: primero se analiza el efecto de las variables de procesado por laser para recubrir Ti6Al4V con polvo de Ti6Al4V y obtener la ventana de procesado, luego se ha estudiado el efecto de la adición de diferentes fracciones de TiC y se han fabricado recubrimientos por solape de cordones, tercero se caracteriza el comportamiento frente a desgaste en seco para determinar las condiciones óptimas de procesado, finalmente se estudia en profundidad las transformaciones metalúrgicas que ocurren en los recubrimientos considerados como óptimos con el fin de proponer posibles mejoras.
Los resultados experimentales muestran que el procesado por laser de titanio requiere un estudio completo para optimizar las condiciones de procesado. Solo mediante un plan de experimentos adecuado ha sido posible triplicar la productividad del proceso y obtener recubrimientos de Ti6Al4V libres de defectos como grietas, poros y oxidación. En este sentido, el uso de helio como gas de
protección supone una ventaja absoluta frente al argón por su mayor potencial de
ionización para evitar la formación de plasma. / Candel Bou, JJ. (2012). ANÁLISIS MICROESTRUCTURAL DE RECUBRIMIENTOS COMPUESTOS DE CARBURO DE TITANIO Y MATRIZ DE TITANIO DEPOSITADOS POR LÁSER [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/14983 / Palancia
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