Engenharia de Materiais
URI permanente desta comunidadehttps://repositorio.fei.edu.br/handle/FEI/17
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4 resultados
Resultados da Pesquisa
- Effects of hydrogen content in nitrogen-based sintering atmosphere on microstructure and mechanical properties of Fe-0.3%C-0.1%B alloy(2014-10-05) LOBERTO, A.; DA SILVA, M. D. C. A.; AMBROZIO FILHO, F.; DE FLORIO, D. Z.; YOSHIMURA, H. N.© (2014) Trans Tech Publications, Switzerland.For the sintered materials, the mechanical properties are strongly dependent on the density of the final product. A substantial reduction of the porosity can be achieved using additives in the powder mixture which promote the formation of a liquid phase during sintering. Boron is a potential liquid phase promoter in ferrous alloys, when sintering is carried out using hydrogen or argon atmospheres. These atmospheres, however, are costly, and the use of nitrogen containing low content of hydrogen could be beneficial. In this study the effects of 10 to 50% hydrogen in nitrogen atmosphere on the microstructure and mechanical properties of a Fe-0.3%C-0.1%B alloy sintered at 1120 and 1250°C were investigated. Boron addition increased the sintered densities, but lowered the transverse rupture strength and hardness in relation to the control alloy (Fe-0.3%C). No significant differences were observed among the samples sintered in different atmospheres for each alloy. Nitrogen containing up to 50% hydrogen atmosphere is not suitable to sinter Fe-C alloy containing boron since it lowers the mechanical properties with the formation of fragile boron nitride precipitates at the grain boundaries and lower perlite fraction.
- Aisi 310 stainless steel formed by gelcasting: An alternative manufacturing method(2020-10-05) RODRIGUES, O. L. F.; NEVEZ, M. D. M.; F. S. Ortega© 2020 Trans Tech Publications Ltd, Switzerland.This work evaluates the microstructure and the yield strength under compression at room temperature and at 800°C of specimens prepared with AISI 310 stainless steel powder (D50 = 10 µm), manufactured by gelcasting. Parts were vacuum sintered in a single batch at 1280°C. At room temperature, specimens presented average yield strength of 270 MPa, and at 800°C, 105 MPa. Microstructure analysis involved the measurement of grain size along the vertical axis of cylindrical specimens, with special attention to the effect of particles settling, and was conducted using scanning electron and optical microscopy, and X-ray diffraction. Settling effect was assessed considering the position where the specimen was taken and was negligible: both density and yield strength did not vary significantly along the vertical axis.
- Gelcasting of stainless steel powder: An alternative to injection molding(2010) Ortega F.S.; Oliveira R.L.S.; Plinio Jr. M.C.; Nobrega B.N.The gelcasting process is a forming technique originally developed for the shaping of advanced ceramics into final products in attempts to overcome some of the limitations of conventional forming techniques used in powder metallurgy. It is based on preparing a high solids loading suspension of powder dispersed in an aqueous organic monomers solution, which is poured into a mold and gelled through a chemically initiated polymerization. This work describes the gelcasting of HK-30 stainless steel, a type of powder commonly processed by injection molding. Large (70 x 30 mm) and geometrically complex green compacts with outstanding form retention and stability were obtained. Sintered parts showed good surface finishing and reached 96% of theoretical density, yield strength of 418.5 MPa, and ultimate strength of 701.5 MPa. These results compare favorably with those typically obtained through conventional powder injection molding of HK-30 feedstocks. They support the growing view that gelcasting may soon become an industrial, low cost alternative for near net shaping metallic powders into small or large parts with complex geometries © (2010) Trans Tech Publications.
- Processing of AISI M2 HSS with addition of NbC by mechanical alloying using two different types of attritor mills(2010) De Araujo Filho O.O.; Das Neves M.D.M.; Gonzalez C.H.; Urtiga Filho S.L.; Ambrozio Filho F.The processing of a molybdenum AISI M2 high speed steel with the addition of NbC (6% in mass) by a Powder Metallurgy technique of Mechanical Alloying is the aim of this work. Mechanical Alloying (MA) has been used primarily for particle size reduction, to its present status as an important method for the preparation of either materials with enhanced physical and mechanical properties or, indeed, new phases, or new engineering materials. In this work, niobium carbide (NbC) was added to the AISI M2 HSS powders by Mechanical Alloying technique in two different types of attritor mills and the materials which resulted were characterized by means of SEM plus EDS. The powders were processed in a horizontal attritor Zoz mill and in a vertical attritor mill developed in our laboratory. The parameters of milling were distinct and the results of the processing were compared. © (2010) Trans Tech Publications.