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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Thermal Debinding of Metal Injection Molded Parts with an Agar-Gel Binder System

Li, Xiaoyun 09 1900 (has links)
This thesis is missing page 48, all other copies of this thesis are missing the page as well. -Digitization Centre / Metal injection molding (MIM) employs the advantages of injection molding and powder metallurgy and provides a high productivity means to form intricate, low-cost, high performance metal parts. One of the most unique characteristics of MIM is the binder system and the consequent debinding step, which is considered to be major process improvement barrier in the MIM process. A MIM part with a thick section suffers from a long debinding cycle and it is difficult to avoid defects. Therefore, it is always of interest to find out a method to quickly debind a thick part without defects. PowderFlo® feedstock combines metal powder with an aqueous agar-gel binder system and requires simple air-drying followed by thermal debinding. However, previous studies on this agar-gel binder feedstock mainly focus on sintering, while the debinding step has lacked sufficient attention. A debinding study on agar-gel binder system is conducted in the present project. The metal compacts are formed via compression molding and injection molding, followed with thermal debinding in order to understand the effects of process parameters on debinding with respect to thickness to determine a good debinding schedule. The thickness transition between thick and thin section is particularly important in the debinding to find a protocol to make parts with both thick and thin sections. Thermal debinding experiments show that the initial heating rate is the most significant factor due to it may cause visible defect directly and an increase of initial and secondary heating rates may retard binder removal. The air-drying time has less influence on binder extraction for thicker section. Extending the holding time for water and polymer removal is beneficial to obtain better dimensional control. The overall debinding process parameters have larger effects on thicker parts. For the thickness transition, it is suggested to avoid the combination of too thin and too thick section, increase the joint area, and provide uniform packing during molding. / Thesis / Master of Applied Science (MASc)
2

Estudos para obtenção da liga NiTi pelo processo de moldagem de pós por injeção

Luna, Wilberth Harold Deza January 2008 (has links)
Os avanços da moldagem de pós por injeção – MPI – associados às excelentes propriedades da liga NiTi abrem novas possibilidades em diferentes áreas da engenharia. A MPI é um processo de fabricação que facilita a elaboração de diversos componentes, podendo-se obter peças de geometrias complexas a um menor custo. O NiTi ou Nitinol® é uma liga que pertence ao grupo dos chamados materiais inteligentes, por ter propriedades como memória de forma e superelasticidade, além disso, essa liga é um material biotolerante por ter titânio na sua composição. O objetivo deste trabalho é estabelecer os parâmetros para a produção de Nitinol® pelo processo MPI visando à confecção de implantes de fixação óssea. Assim, com o objetivo de melhorar o desempenho do processo MPI, este estudo utiliza diferentes cargas injetáveis (feedstock), modificando quantidades de pó na carga injetável e também modificando cada um dos componentes do ligante (binder), de modo a determinar aquela que permite a melhor extração do polímero, corrigindo assim uma das principais fontes de contaminação. A extração química e térmica do ligante é uma etapa também estudada na pesquisa, nessa etapa é analisada a influência da morfologia dos pós na contaminação final das amostras, já que a quantidade de polímero restante após a extração do ligante reagirá diretamente com a matéria prima (Ni – Ti). São estabelecidos ciclos de temperatura para a sinterização da liga. / Advances in Powder Injection Molding (PIM), allied to the great properties of NiTi alloy, offer new possibilities on different areas of engineering. MIP is a process that makes the factory of many compounds easier, allowing to make pieces with complex geometry in minor cost. NiTi or Nitinol® is an alloy that belongs to the “smart materials”, because it has properties as shape memory and superelasticity. Besides, this alloy has good biotollerance because of the titanium. This research means to establish parameters to the production of Nitinol® by PIM process, for bone implants. Therefore, to improve the PIM process, this study applies different feedstock, changing amounts of powder of the injection and also changing each of the components of the binder, in order to determine which one allows the best extraction of the polymer correcting one of prime sources of contamination. Chemical and thermal extraction of the binder was also studied on this research, analyzing the influence of the morphology of the powder on the final contamination of the samples, since the polymer that was left after the binder extraction will react directly with the prime material (Ni-Ti). Temperature cycles are established to the sintering of the alloy.
3

Estudos para obtenção da liga NiTi pelo processo de moldagem de pós por injeção

Luna, Wilberth Harold Deza January 2008 (has links)
Os avanços da moldagem de pós por injeção – MPI – associados às excelentes propriedades da liga NiTi abrem novas possibilidades em diferentes áreas da engenharia. A MPI é um processo de fabricação que facilita a elaboração de diversos componentes, podendo-se obter peças de geometrias complexas a um menor custo. O NiTi ou Nitinol® é uma liga que pertence ao grupo dos chamados materiais inteligentes, por ter propriedades como memória de forma e superelasticidade, além disso, essa liga é um material biotolerante por ter titânio na sua composição. O objetivo deste trabalho é estabelecer os parâmetros para a produção de Nitinol® pelo processo MPI visando à confecção de implantes de fixação óssea. Assim, com o objetivo de melhorar o desempenho do processo MPI, este estudo utiliza diferentes cargas injetáveis (feedstock), modificando quantidades de pó na carga injetável e também modificando cada um dos componentes do ligante (binder), de modo a determinar aquela que permite a melhor extração do polímero, corrigindo assim uma das principais fontes de contaminação. A extração química e térmica do ligante é uma etapa também estudada na pesquisa, nessa etapa é analisada a influência da morfologia dos pós na contaminação final das amostras, já que a quantidade de polímero restante após a extração do ligante reagirá diretamente com a matéria prima (Ni – Ti). São estabelecidos ciclos de temperatura para a sinterização da liga. / Advances in Powder Injection Molding (PIM), allied to the great properties of NiTi alloy, offer new possibilities on different areas of engineering. MIP is a process that makes the factory of many compounds easier, allowing to make pieces with complex geometry in minor cost. NiTi or Nitinol® is an alloy that belongs to the “smart materials”, because it has properties as shape memory and superelasticity. Besides, this alloy has good biotollerance because of the titanium. This research means to establish parameters to the production of Nitinol® by PIM process, for bone implants. Therefore, to improve the PIM process, this study applies different feedstock, changing amounts of powder of the injection and also changing each of the components of the binder, in order to determine which one allows the best extraction of the polymer correcting one of prime sources of contamination. Chemical and thermal extraction of the binder was also studied on this research, analyzing the influence of the morphology of the powder on the final contamination of the samples, since the polymer that was left after the binder extraction will react directly with the prime material (Ni-Ti). Temperature cycles are established to the sintering of the alloy.
4

Estudos para obtenção da liga NiTi pelo processo de moldagem de pós por injeção

Luna, Wilberth Harold Deza January 2008 (has links)
Os avanços da moldagem de pós por injeção – MPI – associados às excelentes propriedades da liga NiTi abrem novas possibilidades em diferentes áreas da engenharia. A MPI é um processo de fabricação que facilita a elaboração de diversos componentes, podendo-se obter peças de geometrias complexas a um menor custo. O NiTi ou Nitinol® é uma liga que pertence ao grupo dos chamados materiais inteligentes, por ter propriedades como memória de forma e superelasticidade, além disso, essa liga é um material biotolerante por ter titânio na sua composição. O objetivo deste trabalho é estabelecer os parâmetros para a produção de Nitinol® pelo processo MPI visando à confecção de implantes de fixação óssea. Assim, com o objetivo de melhorar o desempenho do processo MPI, este estudo utiliza diferentes cargas injetáveis (feedstock), modificando quantidades de pó na carga injetável e também modificando cada um dos componentes do ligante (binder), de modo a determinar aquela que permite a melhor extração do polímero, corrigindo assim uma das principais fontes de contaminação. A extração química e térmica do ligante é uma etapa também estudada na pesquisa, nessa etapa é analisada a influência da morfologia dos pós na contaminação final das amostras, já que a quantidade de polímero restante após a extração do ligante reagirá diretamente com a matéria prima (Ni – Ti). São estabelecidos ciclos de temperatura para a sinterização da liga. / Advances in Powder Injection Molding (PIM), allied to the great properties of NiTi alloy, offer new possibilities on different areas of engineering. MIP is a process that makes the factory of many compounds easier, allowing to make pieces with complex geometry in minor cost. NiTi or Nitinol® is an alloy that belongs to the “smart materials”, because it has properties as shape memory and superelasticity. Besides, this alloy has good biotollerance because of the titanium. This research means to establish parameters to the production of Nitinol® by PIM process, for bone implants. Therefore, to improve the PIM process, this study applies different feedstock, changing amounts of powder of the injection and also changing each of the components of the binder, in order to determine which one allows the best extraction of the polymer correcting one of prime sources of contamination. Chemical and thermal extraction of the binder was also studied on this research, analyzing the influence of the morphology of the powder on the final contamination of the samples, since the polymer that was left after the binder extraction will react directly with the prime material (Ni-Ti). Temperature cycles are established to the sintering of the alloy.
5

Etude, caractérisations et développement de mélanges de polymères biosourcés chargés de poudre d'Inconel 718 pour l'élaboration de composants et micro-composants via moulage par injection de poudres métalliques / Development and characterisation of biosourced polymers binders load with Inconel 718 powder to produce components and micro components by metal injection moulding process

Royer, Alexandre 24 November 2016 (has links)
Ces travaux de thèse concernent l’étude du comportement thermo-physique de mélanges de polymères biosourcés chargés de poudre d’Inconel 718 mis en forme par Moulage par Injection de poudre Métallique. Des matériaux et procédés innovants pouvant permettre une amélioration du procédé ont été étudiés. L’utilisation de polyéthylène glycol (PEG), choisi pour ses propriétés de solubilité dans l’eau, et de polymères biosourcés, pour diminuer l’impact environnemental, ont été choisi. Les nuances de polymères biosourcés ont été choisies adaptées aux conditions du procédé de moulage par injection, il s’agit d’acide polylactique et de polyhydroalcanoates. De même, l’utilisation du CO2 à l’état supercritique comme solvant, a pour objectif de diminuer le temps de déliantage ainsi que d’augmenter la qualité des composants réalisés. Les résultats obtenus ont montré une dégradation du PEG et de l’acide stéarique lors des cycles de mélangeage de de moulage par injection dans les conditions d’utilisation des polymères biosourcés. L’utilisation des mélanges chargés composés de polymères biosourcés ont permis d’améliorer l’homogénéité des composants injectés, mais ont engendré des défauts lors de l’étape de déliantage. Ces défauts ont pu être éliminés par l’utilisation de CO2 à l’état supercritique comme solvant du PEG. Ce dernier procédé a permis une diminution importante du temps de déliantage ainsi qu’une amélioration de la qualité des composants finaux. Les composants densifiés possèdent les propriétés mécaniques correspondantes à l’Inconel 718. / The works done during this PhD focuses on the study of the thermo-physical behavior of bio sourced polymer blends loaded with Inconel 718 powder (feedstock) to be shaped by the Metal Injection Molding process (MIM). First, a review of the researches related to the MIM process was conducted to identify innovative materials and processes that can improve the MIM process. Thus, the use of polyethylene glycol (PEG), selected for its properties of solubility in water, and bio sourced polymers, in order to reduce the environmental impact, were selected. The bio sourced polymers have been selected in accordance with the conditions of the injection molding process, and the choice was made to use polylactic acid (PLA) and polyhydroalkanoates (PHA and PHBV). Similarly, the supercritical CO2 as solvent was chosen to reduce the time of binder removal as well as increasing the quality of components produced. Thermo-physical, mechanical and rheological characterizations were made to determine the behavior of the different feedstock formulations. The results showed a degradation of the PEG and of the stearic acid under the conditions of use of the biopolymers, during the mixing and the injection stages. The use of feedstock made of bio sourced polymers have improved the homogeneity of the injected components, but they have generated defects during the debinding step. These defects have been eliminated by the use of CO2 in the supercritical state as solvent of the PEG. This method has significantly decrease the time of binder removal and improved the quality of the final components. Finally, densified components have the mechanical properties corresponding to Inconel 718.
6

Conformação de pó de aço inoxidável através do processo de injeção à baixa pressão / The low pressure injection molding of stainless steel metallic powder

Ikegami, Rogério Akihide 15 September 2000 (has links)
Metalurgia do pó é o uso de metais na forma de pó para a manufatura de produtos. Pós metálicos são combinados (misturados) e compactados em um molde. O material compactado recebe um tratamento térmico ou é sinterizado em um ambiente controlado para a união das partículas para formar um produto denso e resistente. Injeção de pós metálicos tem se destacado mundialmente na produção de componentes de pequenas dimensões e formas complexas em substituição a fundição sob pressão e a sinterização convencional. Atualmente a injeção de pós metálicos está se tornando uma opção competitiva relativamente à peças fundidas, forjadas, usinadas e estampadas. O presente trabalho revisa as técnicas de injeção de pós metálicos e aplica o processo de injeção à baixa pressão utilizando pó de aço inoxidável 316L com granulometria fina (15 &#956m). Os produtos injetados, uma vez extraídos o VO e sinterizados, foram submetidos à ensaios de tração, dureza e micrográficos. Os resultados obtidos são apresentados e discutidos. O trabalho, para a sua viabilização, incluiu a reforma de uma injetora de bancada à baixa pressão e a construção de moldes de injeção. / Powder metallurgy is the use of metals in the powder form for the manufacture of products. Metallic powders are combined (mixed) and compacted in a die. The compacted material receives a thermal treatment or it is sintered in an controlled atmosphere for the particle binding to form a dense and resistant product. lnjection of metallic powders has if globally highlighted in the production of components of small dimensions and complex forms in substitution the pressure casting and the conventional sintering. Nowadays the injection of metallic powders is becoming relatively a competitive option than casting, forging, machining and stamping. The present work revises the techniques of injection of metallic powders and it applies the injection process to the low pressure using powder of stainless steel 316L with fine granulation (15 &#956m). The injected products, once debinded and sintered, were submitted to tensile test, hardness and micrography. The results are presented and discussed. In this work, included the reform of a low pressure injection machine and construction of injection dies.
7

Conformação de pó de aço inoxidável através do processo de injeção à baixa pressão / The low pressure injection molding of stainless steel metallic powder

Rogério Akihide Ikegami 15 September 2000 (has links)
Metalurgia do pó é o uso de metais na forma de pó para a manufatura de produtos. Pós metálicos são combinados (misturados) e compactados em um molde. O material compactado recebe um tratamento térmico ou é sinterizado em um ambiente controlado para a união das partículas para formar um produto denso e resistente. Injeção de pós metálicos tem se destacado mundialmente na produção de componentes de pequenas dimensões e formas complexas em substituição a fundição sob pressão e a sinterização convencional. Atualmente a injeção de pós metálicos está se tornando uma opção competitiva relativamente à peças fundidas, forjadas, usinadas e estampadas. O presente trabalho revisa as técnicas de injeção de pós metálicos e aplica o processo de injeção à baixa pressão utilizando pó de aço inoxidável 316L com granulometria fina (15 &#956m). Os produtos injetados, uma vez extraídos o VO e sinterizados, foram submetidos à ensaios de tração, dureza e micrográficos. Os resultados obtidos são apresentados e discutidos. O trabalho, para a sua viabilização, incluiu a reforma de uma injetora de bancada à baixa pressão e a construção de moldes de injeção. / Powder metallurgy is the use of metals in the powder form for the manufacture of products. Metallic powders are combined (mixed) and compacted in a die. The compacted material receives a thermal treatment or it is sintered in an controlled atmosphere for the particle binding to form a dense and resistant product. lnjection of metallic powders has if globally highlighted in the production of components of small dimensions and complex forms in substitution the pressure casting and the conventional sintering. Nowadays the injection of metallic powders is becoming relatively a competitive option than casting, forging, machining and stamping. The present work revises the techniques of injection of metallic powders and it applies the injection process to the low pressure using powder of stainless steel 316L with fine granulation (15 &#956m). The injected products, once debinded and sintered, were submitted to tensile test, hardness and micrography. The results are presented and discussed. In this work, included the reform of a low pressure injection machine and construction of injection dies.
8

Process development and optimization towards binder jetting of Vanadis 4 Extra

Jain, Jivesh January 2022 (has links)
Additive manufacturing (AM) has experienced significant growth and development in recent years, owing to the ability to produce complex parts using a wide range of materials with relative ease. Powder bed-based metal AM has been at the forefront of this growth, even reaching the point where parts can be manufactured for end-use applications. Binder jetting (BJ) is one such technique where a liquid binder is selectively deposited on powder layers to create a green body which is then densified using sintering. The aim of this work was to use binder jetting to produce parts using Vanadis 4 Extra, a highly alloyed cold-work tool steel produced by Uddeholm AB for applications involving high demand on abrasive wear. Optimization of the densification parameters, which included debinding atmosphere, debinding temperature, sintering atmosphere, sintering temperature, and sintering time, to achieve full density parts was carried out as the first phase. It was found that the sintering atmosphere and time had the most significant impact on the density of the samples while the debinding atmosphere heavily impacted the C residue from the binder. In the second phase, samples were produced using the optimized parameters for mechanical analysis, which included analyses of the surface roughness and the wear resistance of the binder jetted samples against the conventionally produced samples. The surface roughness was in line with the data presented in literature for binder jetted samples. The binder jetted samples produced during this work exhibited better wear resistance than the conventionally produced samples, with the samples post-processed using hot isostatic pressing showing even better wear resistance. One possible explanation is the diffusion of N from the sintering atmosphere into the samples, leading to the conversion of carbides to carbonitrides and even nitrides. However, further investigation is needed in order to confirm this theory.
9

Experimental investigation and numerical simulation of thermal debinding and sintering processes in powder injection moulding. / Expérimentation et simulation numérique du déliantage thermique et de la densification des composants obtenus par moulage par injection de poudres.

Mamen, Belgacem 10 December 2013 (has links)
L'étape de déliantage est une étape importante et parfois critique pour le procédé Moulage par Injection des Poudres. A cet effet, des analyses thermogravimétriques (TGA) ont été réalisées pour bien comprendre les mécanismes du déliantage thermique sous atmosphère imposée (Argon). Les méthodes de Kissinger et Ozawa ont été utilisées, en se basant sur les résultats des analyses thermogravimétriques, afin d’estimer les paramètres cinétiques nécessaires pour la simulation numérique, notre modèle se propose de décrire les phénomènes physiques liés à la dégradation du polymère, le transfert de chaleur de la déformation du composant pendant le déliantage thermique.La deuxième partie de la thèse est dédiée à la compréhension des mécanismes et du comportement du fritage des composants en tungstène sous une atmosphère d’hydrogène jusqu’à une température de 1 700°C. Des appareils expérimentaux, ont été mis en place afin de constituer une base de données physiques nécessaire pour l’identification des différents paramètres. L’identification de l’ensemble des lois de comportement a été réalisée en prenant en compte les spécificités physiques des poudres utilisées. Un modèle de comportement de type thermo élasto-viscoplastique est formulé pour représenter la loi de densification par diffusion solide, puis appliqué pour les différentes tailles de poudres de tungstène. La dernière étape consiste à valider des simulations numériques avec ABAQUS pour une meilleure détermination des densités et des retraits finaux des composants injectés. / Thermal debinding is one of the most important steps In Powder Injection Moulding process. Thermogravimetric analyses (TGA) are employed to analyze the physics and kinetics of thermal debinding behaviour under argon atmosphere. The Kissinger and Ozawa method have been used to estimate the kinetic parameters from thermogravimetric experiments. To set up the numerical simulations of thermal debinding stage using finite element method, a coupled mathematical has been developed. The basic steps of the proposed model consist to solve the following sequences of coupled problems: themal degradation of binder coupled with heat transfer and deformation phenomena by finite element method using Comsol Multiphysics software.In the second part of this thesis, sintering behaviour of tungsten powders injection moulded component, under pure hydrogen atmosphere at temperature up to 1700°C. The experimental tests are used to determine the material parameters in the parameters in the viscoplastic constitutive law, which is incorporated with the identified parameters in order to simulate the final shrinkages and densities of tungsten injection moulded components during the sintering process. Comparison between the numerical simulations results and experimental ones, in term of shrinkages and sintered densities, shows a good agreement.
10

Herstellung und Eigenschaften neuartiger, metallischer Polyederzellstrukturen

Reinfried, Matthias 01 November 2010 (has links) (PDF)
Das Ziel der vorliegenden Arbeit ist es, die technologischen Schritte für die Herstellung eines geschlossenzelligen metallischen Werkstoffs aus Stahl zu untersuchen. Das Eigenschaftsbild dieses neuartigen zellular aufgebauten Werkstoffs soll umfassend beschrieben und mit bereits existierenden Werkstoffkonzepten verglichen werden. Die Grundidee für die Herstellung einer geschlossenzelligen Struktur bildet die Kombination der Technologie zur Herstellung von metallischen Hohlkugeln und Hohlkugelstrukturen mit dem Herstellungsprozesses für Partikelschäume aus expandierbarem Polystyrol (EPS). Dazu ist es notwendig zunächst Grünkugeln herzustellen, wie bei der Technologie der Hohlkugeln, wobei jedoch ein treibmittelhaltiges EPS zum Einsatz kommt, das mit einer Beschichtung aus Metallpulver und Binder versehen wird. Anschließend sollen die Grünkugeln in einer geschlossenen Form zum expandieren gebracht werden. Dazu wird, wie bei der Partikelschaumtechnologie für Teile aus expandierbarem Polystyrol (EPS), Wasserdampf verwendet. Der durch den Temperaturanstieg und das Treibmittel der EPS-Partikel in den Grünkugeln entstehende Innendruck führt zum Aufschäumen und zur Expansion jeder Grünkugel. In der Folge ändert jede Kugel ihre Form so lange, bis sie mit allen Nachbarn einen flächigen, stabilen Kontakt bildet. Der auf diesem Weg erzeugte Grünkörper kann dann entformt und getrocknet werden. Wie bei der Hohlkugeltechnologie muss nachträglich das EPS durch die thermische Entbinderung entfernt und das Metallpulverskelett zu dichten Zellwänden gesintert werden. Für die Umsetzung dieser Idee ist es erforderlich, ein geeignetes Bindersystem für die Metallpulver-Binder-Beschichtung zu entwickeln, welches die Formänderung während des Schäumprozess unbeschädigt übersteht, sowie den Schäumprozess entsprechend anzupassen. Damit wäre die Möglichkeit gegeben, einen geschlossenzelligen metallischen Werkstoff herzustellen. Er würde die Vorteile einer geschlossenzelligen Struktur und die Materialvielfalt der pulvermetallurgischen Technologie der Hohlkugelherstellung (insbesondere in Bezug auf Stähle und andere höherschmelzende Werkstoffe) miteinander verbinden. In Vorversuchen wurde bereits gezeigt, dass die der Arbeit zugrunde liegenden Ideen realisierbar sind. Mit der vorliegenden Arbeit wird jedoch erstmals die vollständige Kette der technologischen Schritte hinsichtlich der relevanten Einflussgrößen untersucht, wobei großen Wert auf eine Umsetzbarkeit auch im industriellen Maßstab gelegt wird. Für den praktischen Einsatz des geschlossenzelligen Metallschaums sind seine mechanischen Kennwerte, sowie die sie beeinflussenden Herstellungsparameter von grundlegender Bedeutung. Dazu soll die Charakterisierung der zellularen Struktur und des Gefüges des Zellwandmaterials erfolgen. Hauptsächlich soll das Verformungsverhalten mit Hilfe von Druckversuchen untersucht werden. Die Festigkeitskennwerte, das Energieabsorptionsvermögen und die Steifigkeit des zellularen Werkstoffes sind weitere zu untersuchende Kenngrößen. Anhand der Ergebnisse wird eine Einordnung gegenüber dem Stand der Technik der Metallschäume vorgenommen.

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