EM - Escola de Minas
URI permanente desta comunidadehttp://www.hml.repositorio.ufop.br/handle/123456789/6
Notícias
A Escola de Minas de Ouro Preto foi fundada pelo cientista Claude Henri Gorceix e inaugurada em 12 de outubro de 1876.
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Resultados da Pesquisa
Item Effect of Nb addition on the machinability of a pearlitic gray cast iron.(2022) Reis, Bárbara Cristina Mendanha; Santos, Anderson Júnior dos; Pereira, Natália Fernanda Santos; Carmo, Denilson José do; Faria, Geraldo Lúcio de; Câmara, Marcelo Araújo; Faria, Paulo Eustáquio de; Abrão, Alexandre MendesDue to its high thermal conductivity, good damping performance and superior machinability, gray cast iron (GCI) has found many applications in the automotive industry. However, this material has given way to other cast irons due to the need for materials with higher mechanical strength and toughness. Actual efforts have been made to reformulate the GCI chemical composition to obtain different microstructures for improving its mechanical properties. In this study, the influence of Nb content on the microstructure and machinability of GCI was investigated when turning under cutting speeds of 240, 360, and 480 m/min, feed rates of 0.25 and 0.50 mm/rev, and using two different chip breaker geometries (Flat Top and GH). The Nb addition decreased the graphite size and refined the pearlitic interlamellar spacing. However, it did not produce significant alteration in the number of eutectic cells and hardness. Regardless of the Nb content, the presence of chip breaker GH and the lower levels of cutting speed and feed rate were associated with superior machinability. The increase in the Nb content in the GCI raised all the components of the machining forces, yet it did not promote significant changes in the chip temperature and decreased the surface roughness after turning.Item Erosion by solid particle impingement : experimental results with cast-iron, laser-treated surfaces.(1997) Costa, Adilson Rodrigues da; Vilar, RuiThe surfaces of cast-iron specimens have been modified by CO2 laser processing in order to enhance their hardness, providing different surfaces for wear behaviour studies. Various laser heat treatmentswere performed in order to generate distinctmicrostruc- tures. Based on previous tests, interaction time and power density usedwere 0.5 s and 0.4 kW/mm2, respectively. Alloyingwith pure Cr allowed microstructure and the chemical composition of the material to be modified in order to attain the desired properties. Chromium^iron carbides, (Cr,Fe)7C3, formed ``in situ'', during laser surface melting, by reaction with carbon of the cast iron, change the wear properties. These carbides were detected by conventional X-ray diffraction. The expected effect of a carbide-rich structure on the erosion behaviour is to decrease themass loss by erosionmechanisms. Erosion was done by SiC erosive blast impin- gement tests. In this method the SiC particles were accelerated in a compressed air stream along a nozzle and projected against the surface to be eroded. After the laser treatment, the erosion behaviour of material was evaluated by measuring the weight loss. The wear test was complemented by SEMmicrostructural observations. Experiments performed in this work show that, in erosion, the mass loss of material does not depend on hardness as proposed by the accepted tribological theories. The worst behaviour was observed for laser-treated surfaces. Embedding of erodent particles plays a decisive role in blast erosion performance of the surfaces studied.