Laser joining processes, such as brazing and welding, are a common application in industry, especially in the automotive industry. These processes are the key to lightweight and efficient design with regard to the automotive industry. There, laser brazing is used mainly for visible joints due to the superior paint adhesion and surface roughness of brazed joints compared to welds. As laser brazing is applied in the automotive industry without using any fluxes or shielding gas, this leads to a difficulty in maintaining and ensuring the quality of brazed joints.

Les maladies neurodégénératives sont en forte progression dans nos sociétés, mais elles sont également mieux connues et mieux soignées. Par exemple, la stimulation cérébrale profonde est de nos jours utilisée pour lutter contre des maladies comme la maladie de Parkinson. Pour cela, un boitier semblable à celui d'un pacemaker, placé sous la clavicule, est habituellement utilisé pour délivrer des impulsions électriques dans des zones spécifiques du cerveau grâce à des électrodes. Afin d'éviter certaines complications, un boitier ultrafin a été imaginé. Il peut être placé directement au niveau du crâne, au plus proche de la zone à traiter. Les matériaux composant ce boitier doivent présenter certaines caractéristiques. Nous avons choisi de travailler avec des feuilles de TA6V et de zircone yttriée et avons réalisé un assemblage hermétique par l'obtention d'une brasure fine en Ti2Ni.Les feuilles de zircone yttriée présentent des propriétés remarquables mais elles sont notoirement dégradées par un vieillissement hydrothermal. Une étude en vieillissement accéléré a été réalisée sur les feuilles de zircone telles que reçues mais également dans des conditions proches de l'utilisation. Le vieillissement mesuré est suffisamment limité pour envisager une utilisation in vivo, avec cependant une réserve concernant les zircones sous-stœchiométriques. Enfin, le profil de vieillissement et sa vitesse de progression ont pu être précisés.L'assemblage TA6V-zircone a été réalisé par brasage réactif in situ via l'apport initial en nickel pur et la création d'un joint de brasage en Ti2Ni. Le système TA6V-Ni-ZrO2 met en jeu plusieurs phénomènes, que nous avons cherché à déconvoluer : diffusion (solide et liquide), formation et croissance d'intermétalliques et réactions d'oxydo-réduction. La croissance des intermétalliques à partir du couple TA6V-Ni a été particulièrement étudiée. Cela a permis de relier certains événements à la température et de préciser les vitesses de croissance du Ti2Ni (selon son état physique). Grâce à l'ensemble des résultats, un procédé de brasage métal-céramique adapté aux matériaux ultrafins a été d'identifié et réalisé sur système avec succès. / Neurodegenerative diseases are increasingly present in our society but they are also better known and treated. For example, deep brain stimulation is nowadays used to treat diseases such as Parkinson disease. For this purpose, a pacemaker-like device localized in the infraclavicular region is commonly used to deliver electrical pulses in concerned area of the brain thanks to electrodes. In order to avoid some complications, an ultrathin housing was designed. It could be directly implanted under the scalp, close to the area to be treated. Materials of the housing have to be display some features. TA6V, yttria-stabilized zirconia sheets and a hermetic brazing with a Ti2Ni joint were selected to develop this housing.Yttria-stabilized zirconia sheets have remarkable properties but they undergo a degradation caused by hydrothermal aging. An accelerated aging study was done on pristine sheets but also under near-reality conditions. The observed aging is sufficiently limited to consider an in vivo application, subject to one reservation for the under-stoichiometric zirconia. Finally, the aging profile and the propagation rate were specified.The TA6V-zirconia joining was obtained by an in situ reactive brazing, thanks to a filler metal in pure nickel and the formation of a Ti2Ni joint. Several phenomena occur in the TA6V-Ni-ZrO2 system, which were separately studied: (solid and liquid) diffusion, formation and growth of intermetallic compounds and redox reactions. The intermetallic compounds growth from the TA6V-Ni couple was studied in detail. Thanks to all of the results, a metal-ceramic brazing process for ultrathin materials was identified and successfully achieved on our system.

Esta avaliação buscou validar a técnica de retrabalho utilizada no processo de fabricação de evaporadores automotivos, onde a falha na operação de brasagem e tratamento térmico é um dos principais motivos para o alto índice de sucata. A técnica de retrabalho consiste em refazer a operação de brasagem e tratamento térmico nos evaporadores que apresentaram falhas no teste de estanqueidade. Os evaporadores foram submetidos ao processo de rebrasagem em forno de brasagem NOCOLOK e o tratamento superficial em forno de tratamento térmico e avaliados por meio de teste de estanqueidade, utilizando-se gás Hélio (He) à pressão de 16bar e ensaio metalográfico comparativo entre peças produzidas com o ciclo normal de brasagem e tratamento térmico e com o ciclo de rebrasagem, avaliando as modificações nas juntas brasadas. Os resultados obtidos nos 05 experimentos demonstraram que houve modificações significativas nas juntas brasadas após os evaporadores terem sidos submetidos ao processo normal de brasagem, seguido de mais 04 ciclos de rebrasagem e tratamento térmico. Portanto, para a fabricação dos evaporadores automotivos fica recomendado a execução de brasagem e no máximo uma rebrasagem, eliminando a possibilidade de execução de novas rebrasagens. / This evaluation sought the validation of the rework technique used in automotive evaporators manufacturing, where this failure on brazing operation is a main reason to high level of scrap. The rework technique consists in redoing the brazing operation and thermal treatment on evaporators which fail the leak test. The evaporators were subjected to rebrazing process in NOCOLOK furnace and surface treatment in thermal treatment furnace and evaluated through leak test device, using Helium (He) at 16bar of pressure and metallographic test to compare normally produced parts with rebrazing ones, evaluating the structural changes of the material. The results got from 05 experiments made showed that there were significant changes in the brazing joint, after the evaporators being subjected to the normal brazing process, followed by 04 more rebrazing cycles and thermal treatment. Therefore, for the automotive evaporators manufacturing the brazing execution is recommended and at the most a rebrazing, eliminating the possibility of execution of new rebrazing.

Este estudo avaliou a precisão de duas técnicas de união, a brasagem e a soldagem a laser, em estruturas metálicas de uma prótese clássica de Brånemark. Dez estruturas fundidas em NiCr foram segmentadas em 4 partes e analisadas no MEV em pontos pré-estabelecidos, vestibular e proximal, totalizando 8 pontos de análise para cada estrutura. Na primeira fase, foi mensurada a fenda marginal existente entre o análogo do implante e o abutment UCLA antes da união destes segmentos através da brasagem e da soldagem a laser. Após esta análise inicial, as 10 estruturas foram divididas aleatoriamente em dois grupos. O grupo que seria unido pelo processo da brasagem, utilizando maçarico gás/oxigênio, apresentou uma fenda marginal média de 5,94µm, já o grupo que seria unido através da soldagem a laser, uma fenda marginal média de 7,22µm. Os segmentos de cada estrutura metálica foram parafusados com 10Ncm aos respectivos análogos da plataforma de trabalho e unidos com resina acrílica Pattern Resin LS (GC America Inc, USA). Após a polimerização da resina, a estrutura foi desparafusada e submetida ao processo da brasagem ou da soldagem a laser e analisada no MEV nas mesmas posições pré-estabelecidas antes da união. Esta análise foi realizada na mesma plataforma de trabalho. Para tal, os quatro parafusos de fixação foram rotacionados até que fosse detectada uma leve resistência. Neste momento, somente o parafuso de uma das extremidades recebeu um torque de 10Ncm e os demais parafusos foram soltos. A média das fendas marginais após o processo da brasagem passou a ser de 18,80µm e a média das fendas marginais após a soldagem a laser passou a ser de 12,38µm. A análise de covariância mostrou que a diferença das fendas depois e antes da união através da brasagem foi maior que a diferença das fendas obtidas através da soldagem a laser (p = 0,001). Apesar da brasagem apresentar uma distorção significativamente maior quando comparada à soldagem a laser, ambas mostraram valores de fenda marginal clinicamente aceitáveis. No entanto, ficou evidente a facilidade de execução da técnica a laser em relação à brasagem, principalmente no que tange ao tempo necessário para a realização de cada uma delas. / In this study we assess precision of two union techniques, brazing and laser welding, in metallic structures of a Brånemark classical prosthesis. Ten structures cast in NiCr were segmented in four parts and analyzed in the SEM in pre-established points, vestibular and proximal, in a total of 8 analysis points for each structure. In this first phase, we measured the marginal fissure between the implant analogous and the UCLA abutment before the union of these segments using brazing and laser welding. After this initial analysis, we randomly divided the ten structures in two groups. The group that would be united by the process of brazing, using gas/oxygen blowpipe, presented an average marginal fissure of 5,94µm and the group that would be united by laser welding, an average marginal fissure of 7,22µm. The segments of each metallic structure were screwed with 10Ncm to the respective analogous of the work platform and united with acrylic resin Pattern Resin LS (GC America Inc., USA). After polymerization of the resin, the structure was unscrewed and submitted to process of brazing or laser welding and analyzed in the SEM in the same positions pre-established before the union. This analysis was made in the same work platform. To do so we rotated the four fixation screws until we felt a light resistance. At this moment, only the screw of one of the edges received a torque of 10Ncm and the other screws were released. The average of the marginal fissures after the brazing process was 18,80 µm and the average of the marginal fissures after the laser welding process was 12,38µm. The analysis of the covariance showed that the difference of the fissures after and before the union using brazing was bigger than the difference of the fissures obtained with the laser welding (p = 0,001). Despite the fact that the brazing presents a distortion significantly bigger when compared to the laser welding, both techniques showed clinically acceptable values of marginal fissures. However, it is clear how easy the execution of the laser technique is in relation to the brazing, mainly in relation to the time that is needed for each technique.

One of the many promising applications of metal/ceramic joining is in biomedical implantable devices. This work is focused on vacuum brazing of C.P titanium to 96% alumina ceramic using pure gold as the filler metal. A novel method of brazing is developed where resistance heating of C.P titanium is done inside a thermal evaporator using a Ta heating electrode. The design of electrode is optimized using Ansys resistive heating simulations. The materials chosen in this study are biocompatible and have prior history in implantable devices approved by FDA. This research is part of Boston Retinal implant project to make a biocompatible implantable device (www.bostonretina.org). Pure gold braze has been used in the construction of single terminal feedthrough in low density hermetic packages utilizing a single platinum pin brazed to an alumina or sapphire ceramic donut ( brazed to a titanium case or ferrule for many years in implantable pacemakers. Pure gold (99.99%) brazing of 96% alumina ceramic with CP titanium has been performed and evaluated in this dissertation. Brazing has been done by using electrical resistance heating. The 96% alumina ceramic disk was manufactured by high temperature cofired ceramic (HTCC) processing while the Ti ferrule and gold performs were purchased from outside. Hermetic joints having leak rate of the order of 1.6 X 10-8 atm-cc/ sec on a helium leak detector were measured. Alumina ceramics made by HTCC processing were centreless grounded utilizing 800 grit diamond wheel to provide a smooth surface for sputtering of a thin film of Nb. Since pure alumina demonstrates no adhesion or wetting to gold, an adhesion layer must be used on the alumina surface. Niobium (Nb), Tantalum (Ta) and Tungsten (W) were chosen for evaluation since all are refractory (less dissolution into molten gold), all form stable oxides (necessary for adhesion to alumina) and all are readily thin film deposited as metals. Wetting studies are also performed to determine the wetting angle of pure gold to Ti, Ta, Nb and W substrates. Nano tribological scratch testing of thin film of Nb (which demonstrated the best wetting properties towards gold) on polished 96% alumina ceramic is performed to determine the adhesion strength of thin film to the substrate. The wetting studies also determined the thickness of the intermetallic compounds layers formed between Ti and gold, reaction microstructure and the dissolution of the metal into the molten gold.

The project elaborated in frame of engineering studies of the subject M-STG Mechanical Engineering describes elementary methods of joining in the automotive industry. Moreover, it inquires into optimization of laser brazing on the back cover ŠKODA Superb. During the optimization of the process six samples were designed, and the adjustment of the brazing parameters were performed. Consequently, the samples were evaluated by tensile and metallographic tests. Finally, EDS analysis was performed and visual assessment as well.

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In der vorliegenden Arbeit wird ausgehend vom Stand der Wissenschaft und Technik für Ver-fahren und Werkstoffe des Titanlötens das Kaltgasspritzen in seiner Eignung als Vorbelo-tungsprozess beim löttechnischen Fügen von Titanlegierungen untersucht und qualifiziert. Die Parameter des Beschichtungsvorgangs werden dabei mit den resultierenden Schichtgefügen und späteren Lötergebnissen korreliert, wodurch eine Bewertung ermöglicht und ein Beitrag zum Verständnis der Mechanismen einer spritztechnischen Vorbelotung geliefert wird. Es werden dabei sowohl materialografische als auch mechanische Charakterisierungen durchge-führt. Ergänzt werden die Arbeitspunkte durch eine hochauflösende TEM-Untersuchung der Grenzfläche von kaltgasgespritzten Zink-Schichten und Aluminium-Substraten, die der Über-prüfung theoretischer Erkenntnisse zum Haftungsmechanismus kaltgasgespritzter metallischer Schichten auf Leichtmetallsubstraten dient. Die Arbeit schließt mit einer Diskussion und Fol-gerung und gibt Empfehlungen für weiterführende Forschungen auf diesem Gebiet. / The present work qualifies the cold gas dynamic spray process (CGS) as a process for the application of braze filler coatings onto titanium alloy substrates. The work program results from needs and problems that were identified in the state-of-the-art of science and technology. The parameters of the coating process are correlated with the resulting coating microstruc-tures and the posterior brazing results. Materialographic and mechanic characterisations of the filler coatings and braze seams are carried out. Thereby, an evaluation of the braze filler ap-plication by cold gas spraying is permitted. In addition, high-resolution TEM investigations within the interfaces of a cold sprayed zinc coating and an aluminium base material proof the theory of the bonding mechanisms of CGS coatings on light weight metals. The work dis-cusses the achieved results and gives an outlook to continuative investigations in this field of science.

Für den Prozeß des Fügens von Keramik bzw. Keramik mit Metall ergeben sich zahlreiche Probleme, die aus den Eigenschaften der Keramik und den Eigenschaftsdifferenzen zwischen Keramik und Metall resultieren. Unterschiedliche physikalische und mechanische Werkstoffkennwerte bewirken ein zumeist hohes Eigenspannungsniveau des Verbundes, welches in Verbindung mit dem spröden Bruchverhalten keramischer Materialien deren Fügbarkeit verhindert oder einschränkt. Als aussichtsreicher Ansatz bietet sich die Eigenschaftsanpassung des Aktivlotes durch dessen Modifikation mit verstärkenden Materialien an. Es wird ein Konzept für die Herstellung und den Einsatz verstärkter Aktivlote vorgestellt. Theoretische Grundlagen werden durch die Berechnung der Eigenschaften derartiger Lote auf der Basis bewährter Methoden der Verbundwerkstofftheorien geschaffen. Die Simulation mechanisch-thermischer Eigenschaften von Lötverbindungen mit verstärkten Aktivloten unter Einsatz der Methode der finiten Elemente dient dem Erfassen des Spannungsverhaltens. Richtlinien für die Wahl geeigneter Verstärkungskomponenten werden festgelegt. Es wird ein Überblick über geeignete Herstellungsmethoden, deren praktische Realisierung und die Wechselwirkung mit dem Prozeß des Aktivlötens gegeben. Die Bewertung von Aktivlötverbindungen mit verstärkten Loten im Vergleich zu herkömmlichen Verfahren wird auf Grundlage der Ergebnisse von Festigkeitsuntersuchungen vorgenommen.