Navegando por Autor "Klein, A. N."
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Artigo Brazing Al2O3 to sintered Fe-Ni-Co alloys(Springer, 1999-12) Nascimento, Rubens Maribondo do; Martinelli, Antonio Eduardo; Bushinelli, Augusto José de Almeida; Klein, A. N.Active metal brazing has been widely used to join ceramics to metals, as sound joints are usually achieved in a single step process without special equipment. However, residual stresses may be a potential problem especially upon joining ceramics to alloys with relatively high thermal expansion coefficients. This work investigates the brazing behavior of Alumina (Al2O3) to a sintered Fe-Ni-Co alloy, specially designed to match its coefficient of thermal expansion to that of the ceramic counterpart. The results indicate the presence of an interfacial zone whose microstructure depends on the filler alloy employed. A relationship was established between the microstructure of the interface and the flexural strength of the jointsArtigo Plasma nitriding of surface Mo-Enriched sintered iron(Hindawi, 2011-08-09) Bendo, T.; Pavanati, H. C.; Klein, A. N.; Martinelli, Antonio Eduardo; Maliska, A. M.Plain iron samples produced by powder metallurgy were submitted to a single thermal cycle involving plasma-assisted sintering and simultaneous surface alloying with Mo followed by nitriding using a plasma reactor. The microstructural characterization of the samples was carried out by optical and scanning electron microscopy in addition to X-ray diffraction. Microhardness tests were also performed. EDX line profiles of the concentration of Mo from the surface to the bulk of the sintered samples showed that the alloying element diffused down to depths of about 25 μm under the sintering conditions applied. A significant increase in microhardness was observed for samples enriched with Mo and subsequently nitrided. This behavior was attributed to the precipitation of nitrides and the presence of Mo in solid solution