Papers by Keyword: Plasma Sintering

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Authors: T.M.P. Frota, R.A. Brito, Clodomiro Alves Jr., V. Hajek
Abstract: Porous materials are successfully utilized for fabrication of many industrial components such as filters and selflubricating bearings. These products are made by powder metallurgy, where mixtured or prealloyed powders can be used. The aluminum bronze is one of the most wanted due its excellent properties in combination with low cost of the raw materials. In this work, single action compacted (100 MPa) prealloyed aluminum bronze (Cu- 9wt%Al-1wt%Fe) cylinders were sintered using a hollow cathode discharge at temperatures between 400 and 750°C with duration on the isotherm for 12 min. Microstructure changes, homogeneity, porosity and composition were analyzed after the treatment. Sintering below 550° C led to uniform but porous structure. Above 550 °C it was observed a solidified central region and a porous structure that changes slightly through out the cross-section. The diameter of the central region increased with treatment temperature. It is concluded that due to the intense plasma heating and subsequent surface melt formation a mass flow direction to the center of compacts occurred.
Authors: Domingos S. Paulo, Antonio Eduardo Martinelli, Clodomiro Alves Jr., Jorge H. Echude-Silva, C.A.M. Assunção, Michelle P. Távora
Authors: Ariadne de Souza Silva, Edalmy Oliveira de Almeida, Uilame Umbelino Gomes, José F. Silva Jr, Indira Aritana Fernandes de Medeiros
Abstract: Particle reinforced metal matrix composites have received considerable interest over many years and continue still under constant development to gain wider industrial applications. New technique of production of carbetos of refractory metals (WC, NbC, TaC, TaxNby) has been developed, synthesizing nanostructured carbides that show improvement of diverse properties of the materials to the gotten ones for the conventional processes. The properties of sintered composites are determined not only by the nature and quality of the raw materials employed but also by microstructure and porosity resulting from the processing techniques e sintering method. In this study, additions of 20 wt% NbC nanoparticles or micro-particles in the ferrite matrix were performed with the aim of improving the mechanical and use properties. Ancorsteel Fe 1000B powder from Hoengans Corp. was used together with the graphite, and a small amount of Fe3P, to induce liquid phase sintering. NbC nanoparticles or micro-particles were inserted into the Fe 1000B matrix by wet grinding (acetone) in a mill of planetary type of high energy. The angular velocity of the mill was kept constant at 300 rpm with milling time of 10 hours. The composites powders milled were annealed at 900 ° C for 1 hour under flowing hydrogen e argon, and a priori were pressed into cylindrical pellets under 600 MPa and sintered the plasma. Finally, the sintered pellets were evaluated through the testing: SEM, microhardness and density. It was noticeable the behavior of the composites Fe 1000B - NbC was affected by the content of nanoparticles of NbC added as well as by processing parameters, particularly plasma sintering.
Authors: V.J. Batista, M. Mafra, J.L.R. Muzart, Aloísio Nelmo Klein, N. Back
Authors: Domingos S. Paulo, Antonio Eduardo Martinelli, Clodomiro Alves Jr., Jorge H. Echude-Silva, Michelle P. Távora, Rubens Maribondo Nascimento
Abstract: Powdered steel reinforced by NbC dispersed particles was sintered both in resistive furnace at 1180°C or in plasma reactor at 850°C (reference temperature) using heating rates that ranged from 10 to 100°C/min. Fe3P was used as liquid phase sintering additive. The microstructure of the resulting materials was visualized by scanning electronic microscopy. Distinctive microstructural features were observed as a function of the heating source and heating rate. Plasma sintering at rates ~ 30°C/min revealed different microstructural features comparing edge and sample bulk. Homogeneous mixtures of Fe and NbC could be sintered in resistive furnace and plasma reactor using relatively low heating rates. Plasma sintering at 800°C for 1 h (heating rate of 10°C/min) resulted in relative densities of ~ 91% of the theoretical density of the composite. Sintering in resistive furnace for 1150°C resulted in relative densities ~ 94%.
Authors: S.F. Brunatto, Ingeborg Kühn, Aloísio Nelmo Klein, J.L.R. Muzart
Authors: Caubi Ferreira De Souza Jr., Clodomiro Alves Jr.
Authors: Francisco Cruz-Gandarilla, R. Gayosso-Armenta, Miguel Hesiquio-Garduño, J. Gerardo Cabañas-Moreno, Roberto Martínez-Sánchez
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