Engenharia de Materiais
URI permanente desta comunidadehttps://repositorio.fei.edu.br/handle/FEI/17
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2 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.
- Effects of milling time on microstructure and mechanical properties of composite WC-(Fe3Al-B) consolidated by spark plasma sintering(2017-11-08) YBARRA, L. A. C.; CHIMANSKI, A.; PEREIRA, G. J.; MACHADO I. F.; YOSHIMURA, H. N.© 2017 Trans Tech Publications, Switzerland.Cobalt is widely used to produce WC-Co hard metals, but this binder has problems of shortage and unstable price. In this work, cobalt was replaced by an iron aluminide intermetallic binder. WC-10%(Fe3Al-3%B) composite was prepared by vibration milling of WC, Fe, Fe-B, and Al powders and sintered by spark plasma sintering (SPS) at 1150 °C for 8 min under 30 MPa. The milling time was 0.17, 12, 25 and 50 h. The SPS was efficient to consolidate the composite resulting in relative density of ~98% or higher. With increasing milling time, Vickers hardness (HV30) of composite increased from 12 to 14 GPa due to the enhanced homogeneity of microstructure, while the fracture toughness, KIc, determined by an indention fracture method using Shetty equation, remained constant at around 9.1 MPa.m1/2.