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Previous issue date: 2017-07-28 / As propriedades ?nicas do comp?sito de matriz met?lica de cobre (Cu) refor?ada
por dispers?o de part?culas de carboneto de tungst?nio (WC) s?o de grande import?ncia
para v?rias aplica??es industriais, devido a sua excelente resist?ncia sob alta temperatura,
boa resist?ncia ? corros?o e ? fratura. O comp?sito Cu-WC ? quimicamente
e termicamente est?vel, al?m de possuir excelentes propriedades de condutividade
t?rmica e el?trica. Tais caracter?sticas o tornam um promissor material para fabrica??o
de contato el?trico de alta pot?ncia, eletrodos para soldagem, condutores de campo
magn?tico pulsado, dispositivos de gerenciamento t?rmico e el?trico. Este trabalho
investiga o efeito da moagem de alta energia na densifica??o e microestrutura dos
comp?sitos WC-20%Cu e WC-18%Cu-2%Nb, bem como a influ?ncia da adi??o do
ni?bio como inibidor de crescimento de gr?o. O efeito da press?o de compacta??o e da
temperatura de sinteriza??o dos p?s preparados por moagem e mistura mec?nica na
densidade tamb?m foram estudados. P?s de WC, Cu e Nb, na raz?o de 80, 20 e 2 por
cento em massa, respectivamente, foram preparados por moagem e, tamb?m, por
mistura mec?nica. A moagem dos p?s comp?sitos foi realizada a seco sob atmosfera
ambiente com um recipiente e bolas de metal duro em um moinho attritor. Os p?s foram
mo?dos a 900 rpm durante 90 minutos e sob uma raz?o de massa p? para bolas de
1:100. Compactos de p?s com forma cil?ndricas foram prensados a 200, 400 e 600
MPa em uma matriz de a?o uniaxial de 8 mm de
di?metro. Os corpos verdes foram sinterizados nas temperaturas de 1030 ?C e 1150 ?C
por 60 min. em forno tubular resistivo sob atmosfera de nitrog?nio. A microestrutura dos
corpos sinterizados foi analisada por microscopia eletr?nica de varredura. Para analisar
a presen?a de impurezas nos p?s elementares e mo?dos, an?lises qu?micas de FRX e
EDS foram realizadas. A an?lise de DRX foi usada para detectar as fases presentes.
Uma significativa diminui??o dos cristalinos e amorfiza??o das fases Cu e WC foi
exibida pelos p?s mo?dos. Assim como, um menor tamanho de gr?o foi alcan?ado
pelas microestruturas sinterizadas dos p?s comp?sitos Cu-WC com adi??o de Nb. Os
compactos de p?s submetidos a maior press?o de compacta??o e temperatura de
sinteriza??o tamb?m alcan?aram as maiores densifica??es. / The unique properties of copper metal matrix composite reinforced by dispersion
tungsten carbide particles (WC) are of great importance for several industrial applications,
due to their excellent high temperature strength and good corrosion and fracture
resistance. This composite is chemically and thermally very stable at high temperatures,
as well as having excellent thermal and electrical conductivity properties. These
promising features make for the manufacture of high-power electrical contact parts,
welding electrodes, magnetic field conductors, thermal and electrical management devices.
This work investigates the effect of high energy milling on the densification and
microstructure of the composites WC-20% Cu and WC-18% Cu-2% Nb as well
as an influence of the addition of niobium as a grain growth inhibitor. The effect of the
compacting pressure and the sintering temperature of the powders prepared by milling
and mechanical mixing in the density were also studied. WC, Cu and Nb powders in the
ratio of 80, 20 and 2 percent by mass, respectively, were prepared by milling and also
mechanical mixing. The powder mixture were mechanically alloyed in a attritor ball mil in
a dry environment. The powders were milled at 900 rpm, with a mass to powder ratio of
1: 100 balls for 1.5 hours, and pressed at 200, 400 and 600 MPa in a uniaxial matrix with
8mm diameter. The green bodies were sintered at temperatures of 1030 ?C and 1150 ?
C for 60 min in a resistive tubular oven under a nitrogen atmosphere. A microstructure
of sintered bodies for analysis by scanning electron microscopy. To analyze a presence
of impurities in the initial powder and the as-milled powders, chemical analyzes
of XRF and EDS were performed. A XRD analysis was used to detect as structure
of crystalline. Amortization of the Cu and WC phases occurred, with a decrease in
the crystalline phase due to milling, and inhibition of grain growth, both at temperatures,
in the samples with Nb. Higher compaction pressure and higher sintering temperature
show better results for densification of the material.
| Identifer | oai:union.ndltd.org:IBICT/oai:repositorio.ufrn.br:123456789/24841 |
| Date | 28 July 2017 |
| Creators | Coelho, Renan S?vio de Almeida |
| Contributors | 45327220478, Silva, Ariadne de Souza, 00735940401, Silva, Gilson Garcia da, 56634161453, Gomes, Uilame Umbelino, 05012180410, 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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