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Previous issue date: 2016-05-30 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior (CAPES) / Os materiais cer?micos, tais como a alumina (Al2O3) e o cobalto (Co), apresentam
caracteristicas relevantes para aplica??o como ferramentas de corte, e dentre
estas se destacam a elevada dureza e o alto ponto de fus?o. No entanto, a sua
aplica??o ? limitada pela sua baixa tenacidade e baixa resist?ncia mec?nica. Desta
forma, a fim de aumentar a tenacidade do material, mantendo-se as elevadas propriedades
mec?nicas, alguns metais, como por exemplo, o cobalto (Co), t?m sido
usados na tentativa de se produzir um material mais tenaz. Neste trabalho, estudouse
o efeito da moagem de alta energia e da adi??o de (%p.) Co na densifica??o e
microestrutura, assim como, nas propriedades mec?nicas do composto Al2O3-Co. Os
p?s-particulados (Al2O3 e Co), com percentuais de 5 e 20%p. de cobalto, foram mo?dos
em um moinho planet?rio durante 50 horas, e amostras de p?s foram coletadas
nos intervalos de 2, 10, 15, 20, 30,40 e 50 horas. Os p?s mo?dos foram caracterizados
por difra??o de raios-X (DRX), an?lises particulom?tricas, microscopia eletr?nica
de varredura (MEV); e compactados em uma matriz cil?ndrica sob uma press?o
uniaxial de 100 MPa. Posteriormente, os compactados a verde foram sinterizados
em um forno resistivo nas temperaturas de 1200 a 1500 ?C, por 60 minutos, sob
uma atmosfera de arg?nio com taxa de aquecimento de 10?C/min. Os corpos de
prova sinterizados foram caracterizados por DRX, MEV e energia dispersiva (EDS).
A densidade foi medida usando o m?todo geom?trico (massa/volume), e os melhores
valores foram obtidos para as amostras sinterizadas a temperatura de 1500 ?C,
sendo a densidade relativa igual a 78 %, seguido das sinterizadas a temperaturas de
1350?C e 1300?C, que apresentaram as respectivas densidades 68 %, e 62 %. / Ceramic materials, such as alumina (Al2O3) and cobalt (Co), present characteristics
like high hardness and the high melting point for application as cutting tools.
However, its application is limited because of its low toughness and low mechanical
strength. Thus, in order to increase the toughness and maintaining the high mechanical
properties, some metals such as cobalt (Co) have been used. In this work, the
effect of the high energy milling and different amount of Co on densification, microstructure
and mechanical properties of the Al2O3-Co compound were studied. The
particulate powders (Al2O3 and Co), with 5 and 20 wt% of cobalt, were milled in a
planetary milling for 50 hours, and powder mixture samples were collected at the intervals
of 2, 10, 15, 20, 30, 40 and 50 hours. The milled powders were characterized
by X-ray diffraction (XRD), particulometric analyzes, scanning electron microscopy
(SEM); And compacted in a cylindrical matrix under a uniaxial pressure of 100 MPa.
Subsequently, green compacts were sintered in a resistance furnace at 1200 to 1500
?C with holding time of 60 minutes under an argon atmosphere with a heating rate of
10 ?C/min. The sintered samples were characterized by XRD, SEM and EDS. Density
was measured using the geometric method (mass/volume), and the best values were
obtained for the samples sintered at 1500 ?C with relative density of 78% compared
with sample sintering at 1350 and 1300 ?C which presented relative densities of 68%
and 62% respectively.
| Identifer | oai:union.ndltd.org:IBICT/oai:repositorio.ufrn.br:123456789/23549 |
| Date | 30 May 2016 |
| Creators | Souza, Jos? Leonaldo de |
| Contributors | 45327220478, http://lattes.cnpq.br/8698567925323942, Silva, Ariadne de Souza, 00735940401, http://lattes.cnpq.br/5623381698478389, Ara?jo Filho, Oscar Olimpio de, 40379469472, http://lattes.cnpq.br/6740759499723367, Costa, Francine Alves da |
| Publisher | PROGRAMA DE P?S-GRADUA??O EM ENGENHARIA MEC?NICA, UFRN, Brasil |
| Source Sets | IBICT Brazilian ETDs |
| Language | Portuguese |
| Detected Language | English |
| Type | info:eu-repo/semantics/publishedVersion, info:eu-repo/semantics/masterThesis |
| Source | reponame:Repositório Institucional da UFRN, instname:Universidade Federal do Rio Grande do Norte, instacron:UFRN |
| Rights | info:eu-repo/semantics/openAccess |
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