Navegando por Autor "Pimenta, Jean Senise"
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Artigo Brasagem da zircônia metalizada com titânio à liga Ti-6Al-4V(ABCERAM, 2012-06) Martinelli, Antonio Eduardo; Pimenta, Jean Senise; Buschinelli, Augusto José de Almeida; Nascimento, Rubens Maribondo do; Reisgen, UweZircônia tetragonal estabilizada com ítria foi mecanicamente metalizada com titânio e a condição de molhamento avaliada com as ligas convencionais Ag-28Cu e Au-18Ni. Estas dissolveram o revestimento de titânio para uma completa distribuição deste metal ativo na superfície cerâmica, gerando uma liga ativa in situ e possibilitando adequadas ligações químicas ao metal base na temperatura de união. Os melhores resultados de molhamento foram selecionados para brasagem indireta em forno de alto-vácuo nas juntas ZrO2/Ti-6Al-4V. Testes de detecção de vazamento de gás hélio foram realizados na interface de união das juntas; amostras removidas na seção transversal de juntas estanques foram examinadas por técnicas de análise microestrutural. Formou-se uma camada escura adjacente à cerâmica metalizada, responsável pelo molhamento ocasionado pela liga Ag-28Cu. Entretanto, o uso da liga Au-18Ni resultou em precipitação de intermetálicos e microtrincamento interfacial. Perfis de microdureza através da interface resultante até onde a zircônia mostrou típico escurecimento não indicaram alternância significativa entre medições consecutivas; os resultados dos ensaios de resistência mecânica à flexão-3p foram considerados satisfatóriosArtigo Brazing of metals to zirconia mechanically metallized with titanium(Associação Brasileira de Engenharia e Ciências Mecânicas - ABCM, 2010) Pimenta, Jean Senise; Buschinelli, Augusto José de Almeida; Nascimento, Rubens Maribondo do; Martinelli, Antônio Eduardo; Remmel, JosefThe mechanical metallization is a successful technique at laboratory scale and specially applied to oxide ceramics. Indirect brazing process of zirconia to metals is achieved using active-metal-free filler alloys on previously metallized ceramic. Stabilized zirconia ceramics were mechanically metallized with Ti and wetting conditions evaluated using commercial Ag-Cu and Au-Ni fillers with its respective thermal cycles. Better results were selected for brazing ceramic to metals in a high-vacuum furnace. Reliable vacuum tight ceramic/metal joints were obtained specially using the Ag-28Cu filler for results below 10-8 mbar.l.s-1; samples at the joint cross-section were examined by microstructural analysis techniques and energy dispersive X-ray analysis. Microhardness profiles were made across the joints interface where zirconia undergone a typical darkening effect during brazing. Microstructure at the braze region revealed a dark reaction layer and precipitation zone closely to metallized ceramic surface for zirconia/Ti-6Al4V joints due to chemical interactions between the individual componentsArtigo Brazing of zirconia to titanium using Ag-Cu and Au-Ni filler alloys(Associação Brasileira de Soldagem, 2013-12) Nascimento, Rubens Maribondo do; Pimenta, Jean Senise; Buschinelli, José de Almeida; Martinelli, Antonio Eduardo; Remmel, JosephAdvanced ceramic is usually joined to metal by the well-known direct brazing process, where costly active filler alloys can be considered a limitation. Brazing using active-metal-free filler alloy as insert between the joint components is an attempt to overcome it. The active metal diffusion from the titanium member through the bulk of molten filler to the ceramic was responsible to produce an active filler alloy in loco and promote reduction of the zirconium oxide to improve wetting on the ceramic surface. Unalloyed titanium was joined in a high-vacuum furnace (<3x10-5 mbar) to yttria-tetragonal zirconia polycristals (Y-TZP) and zirconia partially stabilized with magnesia (Mg-PSZ), where commercial fillers Ag-28Cu and Au-18Ni with respective thermal cycles were evaluated. Helium gas leak detection test was performed at the ceramic/metal interface at room temperature; samples from reliable vacuum tight joints were examined by microstructural analysis techniques and energy dispersive X-ray analysis at the joint cross-section. Tight joints were produced with eutectic Ag-Cu filler, revealing an intermetallic layer and a dark reaction layer near the ceramic surface; titanium diffusion was efficient for superficial chemical interactions between individual components. Brazing joints were also tested using three-point flexure testingDissertação Estudo da influência da temperatura de brasagem nas uniões zircônia/aço inox 304 utilizando metalização mecânica(Universidade Federal do Rio Grande do Norte, 2014-07-30) Carneiro, Jaciane Moraísa; Nascimento, Rubens Maribondo do; ; http://lattes.cnpq.br/8671649752936793; ; http://lattes.cnpq.br/1220495103623444; Buschinelli, Augusto José de Almeida; ; http://lattes.cnpq.br/9684649153800847; Pimenta, Jean Senise; ; http://lattes.cnpq.br/4118125609778962; Pereira, Jorge Carlos Lopes Brás Silva; ; http://lattes.cnpq.br/0732639595855805Interfaces metal/cerâmica zircônia/aço inox processadas via brasagem vêm sendo utilizadas devido a sua combinação de propriedades tais como: estabilidade em altas temperaturas, elevada resistência à corrosão e boas propriedades mecânicas. Contudo, alguns pares apresentam problemas a nível da interface, como trincas, fissuras e porosidades, contribuindo assim para a deterioração do par metal/cerâmica, podendo até conduzir à ruptura total da interface. Esses defeitos na interface podem estar associados a uma seleção menos criteriosa dos parâmetros de brasagem para cada sistema. No presente trabalho utilizou-se a união entre zircônia (Y-TZP e Mg PSZ) com aço inox 304. Essas junções foram metalizadas mecanicamente com Ti e brasadas em diferentes ciclos térmicos utilizando liga de adição Ag-Cu. Microscopia Eletrônica de Varredura (MEV) com microanálise por espectroscopia de Energia Dispersiva (EDS) e teste de flexão em 3 pontos foram empregadas para investigar as propriedades da união zircônia/aço. Os resultados revelaram que para menores temperaturas de brasagem houve uma melhor resistência a flexão e camadas de reação mais homogêneas entre a liga de adição e os pares metal/cerâmica. Ficou também comprovado a ativação in situ da liga de adição AgCuArtigo Joining of zirconia mechanically metallized with titanium(ABCERAM, 2010-07) Pimenta, Jean Senise; Buschinelli, Augusto José de Almeida; Nascimento, Rubens Maribondo do; Martinelli, Antônio Eduardo; Remmel, JosefDirect brazing is a well-known technique for joining ceramics either themselves or to metals, whereby the required costly active filler alloys are considered a handicap of this process. In this work the indirect brazing of zirconia to zirconia mechanically metallized with Ti was successfully achieved using conventional filler alloys. The mechanical metallization specially applied to oxide ceramics is a successfully technique that was patented by Forschungszentrum Juelich, Germany, and it has been the subject of applied researches in the last 10 years. This particular metallization is made at room temperature with low cost production and is environmentally safe. Partially stabilized zirconia with yttria was mechanically metallized with Ti and wetting conditions were evaluated using Ag-28Cu and Au-18Ni fillers. These conventional fillers dissolve part of the Ti-coating becoming on-site at brazing temperature an active filler alloy which reacts with the zirconium oxide to improve wetting on the ceramic surface. Better results were selected for brazing tests in a high-vacuum furnace (< 3×10-5 mbar). Helium gas leak detection was made at the ceramic/ceramic interface at room temperature; samples from reliable vacuum tight joints were examined by microestructural analysis and linescan technique by energy dispersive X-ray analysis in its cross-section. Microhardness profiles were made across the joint interface where zirconia undergone darkening after brazing process. Sound brazed joints were produced even when just one ceramic surface of the joint assemble was previously metallized, due to titanium diffusion from the metallized ceramic surface to the other ceramic side at the joint assemble