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COB8 RELAÇÃO ENTRE LIMITE DE RESISTÊNCIA A FADIGA E LIMITE DE RESISTÊNCIA A TRAÇÃO DE MATERIAIS SINTERIZADOS
Ernani Sales Palma
Departamento de Engenharia Mecânica - UFMG, Av. Antonio Carlos, 6627 - Campus Pampulha, 31.260-901 - Belo Horizonte-MG
E-Mail:ernani@vesper.demec.ufmg.br
The influence of porosity on the relationship S N /s RES for sintered iron and steels are investigated. Data are presented for tensile and fatigue properties in the porosity range 3-14%, in the as sintered conditions. It is observed that the relationship S N /s RES decreases by increasing porosity. This becomes more evident in the sintered steels than in iron. Finally, with exception of Fe, it was shown that experimental results do not fit in the results obtained from a empirical equation take of literature.
COB362 NITROCEMENTAÇÃO POR PLASMA DE FERRO PURO SINTERIZADO / PLASMANITROCARBURIZING OF PURE SINTERED IRON
Elenice C. Borba, Ana M. Maliska, Antônio R. de Souza & Aloísio N. Klein
LABMAT/ Laboratório de Materiais - Depto de Engenharia Mecânica / UFSC, CEP 88015-100, Florianópolis, SC - BRAZIL
Fone: (55) 048 231 9268 - Fax: (55) 048 234 0059, http:/www.labmat.ufsc.br
E-mail: elenice@labmat.ufsc.br, E-mail: ana@labmat.ufsc.br, E-mail: rogerio@labmat.ufsc.br, E-mail: klein@labmat.ufsc.br
The microstructure of the material produced by powder metallurgy in presence in the nitrocarburizing atmosphere is investigated. In order to study the influence of the amount of carbon in the atmosphere for the formation of the treated layer, sintered powdered iron was nitrocarburized in 90N 2 - 10 H 2 atmosphere containing CH 4 in the range from 1 up to 2%. The formation of the surface layer was analysed by plasma nitrocarburizing of pure sintered iron. The samples were treated at 3 Torr, 540 and 570°C, during 1-3 hours, using a dc discharge. The nitrocarburezed layers were examined by standard optical and scanning electron microscopy (SEM), X-ray diffraction and electron probe microanalyse (EPMA). Results have shown that the thickness of compound layer is very sensitive to the temperature rises, with microtructural modification. It was also detected a micropore formation in the outermost compound layer as a result of increasing treatment time.
Keywords: Nitrocementação por plasma, Sinterização, Fase-e, carbonitreto/ Plasma nitrocarburizing, Sintering, Phase-e, carbonitrites
COB608 PROCESSO DE OBTENÇÃO DE COMPOSTOS INTERMETÁLICOS DE Ti E Al UTILIZANDO ONDAS DE CHOQUE / PROCESS OF OBTANING INTERMETALLIC COMPOUNDS OF Ti AND Al BY USING SHOCK WAVES
Arnaldo Ferreira e João Edison Minnicelli
Departamento de Engenharia Mecânica e de Materiais, Instituto Militar de Engenharia - IME.
Praça General Tibúrcio 80, 22290-270, Praia Vermelha, Rio de Janeiro, RJ - Brasil
Elemental powders of Ti and Al were mixtured and, by employing the flyer plate technique, experiments were performed in order to determine the threshold chemical reaction between the powders, and to obtain compacts that allow to characterize the reagents compacted by shock wave. Different proportional mixtures between Ti and Al were used, as an attempt of obtaining improved reactions and better compaction of the materials. The experimental parameter that was varied was explosive quantity, increasing the amount of energy imparted to the powder material. The intermetallic compound TiAl was also mecanically mixtured with Ti and Al powders, in order to compare the compacted material. Analysis by X-Ray diffraction and Scanning Electron Microscopy were performed to determine the chemical changes during the compression by shock waves. Successful consolidation was obtained and was comproved by strong bonding between individual particles. The main parameter that is significant during the process of chemical reaction and the experimental results are presented and discussed.
Keywords: Dynamic Consolidation; Shock Waves; Shock-Induced Chemical Reactions; Ondas de Choque; Metalurgia do Pó.
COB1020 ESTUDO DA DENSIFICAÇÃO DO AÇO INOXIDÁVEL 316L SINTERIZADO EM REATOR DE PLASMA / DENSIFICATION STUDIES OF 316L STAINLESS STEEL SINTERED IN A PLASMA REACTOR
Vilson João Batista, Jorge Hebert Echude Silva, Márcio Mafra, Joel Louis Rene Muzart, Aloísio Nelmo Klein
LABMAT - Pós Graduação em Engenharia Mecânica - UFSC,CEP. 88040-900, Florianópolis, SC, (vilson@labmat.ufsc.br), (echude@matrix.com.br), (mafra@labmat.ufsc.br), (joel@labmat.ufsc.br), (klein@labmat.ufsc.br).
This study shows the consolidation behavior of AISI-316L Stainless Steel sintered in a plasma reactor. Three thermal cycles were followed varying the sintering temperature and time.The final densities obtained here for the 316L- SS sintered by this novel technique were equal or higher than the densities of known steels sintered by conventional routes. Nevertheless, plasma sintering allows a better atmosphere control, as well as energy saving, since only the sintering parts are heated up by the ionized plasma. The main results include densities of the order of 7.39; 7.43 and 7.64 g/cm3 for sintering conditions of 1050 ° C and 1150 ° C during 60 min., and 1270 ° C during 150 min.
Keywords: Plasma; Sinterização, Processo / Plasma; Sintering; Process.
COB1045 COMPORTAMENTO À TRAÇÃO DE FERRO E AÇO SINTERIZADOS NITRETADOS POR PLASMA - PARTE II /TENSILE BEHAVIOR OF PLASMA-NITRIDED SINTERED IRON AND STEEL - PART II
Helio de Brito Costa, Ingeborg Kühn A. & Antonio Rogério de Souza
LABMAT - Depto de Engenharia Mecânica - CTC - UFSC
Caixa Postal 476 / 88040-900 Florianópolis, SC, Brasil, e-mail: <helio@labmat.ufsc.br>,<ingeborg@emc.ufsc.br>
The micromechanisms involved in the tensile fracture of sintered materials submitted to thermochemical treatments have as yet not been clearly established. For this purpose, a scanning-electron fractographic analysis was performed on tension-ruptured sintered specimens of iron and low-alloy molybdenum steel, either nonnitrided or previously plasma nitrided. In order to investigate the effect of some typical microstructures, three different treatment atmospheres were employed, the nitrogen content being varied and a carbon-bearing component being introduced. Results show that nitriding generally favors the operation of fracture micromechanisms of low energy absorption in the near-surface regions. The nature of these mechanisms, their frequency, location and extent, depend on the base material, nitriding atmosphere and, in some cases, also on local porosity features.
Keywords: Plasma Nitriding, Sintered steel, Sintered Iron, Tensile Test, Fracture Micromechanisms.
Nitretação por Plasma, Aço Sinterizado, Ferro Sinterizado, Ensaio de Tração, Micromecanismos de Fratura.
COB1046 COMPORTAMENTO À TRAÇÃO DE FERRO E AÇO SINTERIZADOS NITRETADOS POR PLASMA - PARTE I / TENSILE BEHAVIOR OF PLASMA-NITRIDED SINTERED IRON AND STEEL - PART I
Helio de Brito Costa, Ingeborg Kühn A. & Antonio Rogério de Souza
LABMAT - Depto de Engenharia Mecânica - CTC - UFSC, Caixa Postal 476 / 88040-900 Florianópolis, SC, Brasil
e-mail: <helio@labmat.ufsc.br>,<ingeborg@emc.ufsc.br>
Strength and ductility properties of sintered iron and low-alloy molybdenum steel in four different conditions, one nonnitrided and three nitrided under different gas mixtures (nitogen volume fraction: low - 5% N2 ; medium - 25% N2 ; and high - 75% N2 with added 1,25% CH4 - nitrocarburizing mixture) were evaluated. An increase in strength and a decrease in ductility properties were generally observed in the nitrided conditions as compared to the nonnitrided one, and were also related to the increase of the nitrogen content in the nitriding gas mixture. This behavior was correlated with the microstructural features and the microhardness profiles of the nitrided layers produced by the different treatment conditions under investigation.
Keywords: Plasma Nitriding, Sintered steel, Sintered Iron, Mechanical Properties.
Nitretação por Plasma, Aço Sinterizado, Ferro Sinterizado, Propriedades Mecânicas.
COB1050 DESENVOLVIMENTO DE LIGAS SINTERIZADAS À BASE DE FERRO, FÓSFORO E NÍQUEL PARA APLICAÇÕES DE ENGENHARIA / DEVELOPMENT OF PHOSPHORUS AND NICKEL, IRON BASED SINTERED ALLOYS TO APPLY IN ENGINEERING
Paulo Junho de Oliveira, Júlio Navarro Santos & Edmilson Otoni Corrêa
Departamento de Engenharia Mecânica, Escola Federal de Engenharia de Itajubá - EFEI
CEP 37500-000 Av. BPS, 1303, Pinheirinho, Itajubá, Brasil - E-mail: navarro@iem.efei.rmg.br
In this work the possibility of sintering of iron based alloys with variable contents of nickel and the content of phosphorus kept constant in 0,5% has been examined. This investigation has the aim of developing iron based alloys for use in engineering where the introduction of nickel and phosphorus in a matrix of iron produces materials with a more adequate density and improved strength . The absence of carbon has the objective to make these products be recompactable, with the advantage of na improved final density and a better dimensional control. This fact can avoid the inconvenient of an excessive fragility and abrasivity that could be caused by the simultaneous presence of carbon and phosphorus. The mechanical properties of the mentioned alloys were analyzed . By these results, it was show that, despite the presence of porosity, a reasonable compromise between hardness and tensile strength was obtained and this was better performed for alloys with a nickel content of 4% and 5% .
Keywords: desenvolvimento, ligas ferrosas sinterizadas, Propriedades mecânicas.
Development, iron based sintered alloys, mechanical properties
COB1461 PROCESSAMENTOS ALTERNATIVOS PARA A OBTENÇÃO DE PASTILHAS SUPERCONDUTORAS DO SISTEMA (Bi,Pb):Sr:Ca:Cu:O / ALTERNATIVE PROCESSING TO OBTAIN SUPERCONDUCTING PELLETS OF THE (Bi,Pb):Sr:Ca:Cu:O SYSTEM
DAYSE I. DOS SANTOS & ELISABETE AP. A . RUBO
Departamento de Física, Faculdade de Ciências - UNESP Campus Bauru
CAIXA POSTAL 369 - CEP 17033-360 Bauru - SP - Brasil
E-mail : DAYSE@AZUL.BAURU.UNESP.BR
This work is about the obtaintion and characterization of samples of the Bi:Pb:Sr:Ca:Cu:O ceramic system. The powder was prepared by two processes: oxide/carbonate mixture and oxalate coprecipitation. These two processes were used in order to stablish the most favorable process to the 110 K phase formation. The characterization techniques were Inductively Coupled Plasma, Sedigraphy, X-ray diffraction and scanning electron microscope. The sinterization was made by conventional and an alternative techniques. The alternative one consists in applying an electrical current simultaneously to the temperature action. The expectation was that this technique would accelerate the reactions and, consequently, to promote higher volume fraction of the 110 K phase. The pellets were structural, electrical and magnetically characterized by X-ray diffraction, SEM, electrical resistivity and magnetic susceptibility. In the analysis of the electrical and structural characterization of the pellets made by both processing methods, we could not find any difference between them. But, the magnetization measurements indicated that there are numerous phases with critical temperatures bellow 110 K, in addition to a higher fraction of 2223 phase, in the pellet made by coprecipitation of oxalates. The alternative sintering process promoted only some alterations in the behavior of the electrical resistivity as a function of the temperature.
Keywords: Ceramic Superconductors, superconductor pellets, chemical process, Bi:Sr:Ca:Cu:O.
Supercondutores cerâmicos, pastilhas supercondutoras, processo químico, Bi:Sr:Ca:Cu:O.