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Previous issue date: 2017-10-11 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior (CAPES) / Metal duro do tipo WC-Co ? utilizado na usinagem, perfura??o e ou fabrica??o de
ferramentas de corte. Atualmente, 70% das ferramentas de corte s?o carbetos do tipo WCligante.
Em n?meros de produ??o, aproximadamente 40,000 MT de ferramentas ? base
de WC foram produzidas mundialmente desde 2011. Hoje, mais de 90% da produ??o de
todo o metal duro, do tipo WC-ligante, utiliza o cobalto como ligante principal. A
superioridade do cobalto em rela??o a outros ligantes est? ligada a v?rios fatores, sendo
o principal a largura da janela de carbono no diagrama de fase. As pesquisas por ligantes
alternativos que possam vir a substituir ao menos de forma parcial o cobalto s?o de
extrema import?ncia, devido: ? escassez e pre?o do cobalto e principalmente pelo sistema
WC-Co ser carcinog?nico. O objetivo da referida tese de doutorado foi analisar a
viabilidade do uso dos ligantes alternativos 316L e FeNi com adi??o de cromo no WC.
Ambos os sistemas WC-316L (teores de ligante de 5, 7 e 20%) e WC-20%FeNi com
adi??o de cromo (em 5, 10 e 20%) foram processados pela rota de metalurgia do p?,
seguindo as etapas: prepara??o das misturas, moagem (1h, 24h), compacta??o uniaxial
(200 MPa) e sinteriza??o a v?cuo (1400oC/1h). As caracteriza??es realizadas em todas as
amostras sinterizadas foram: microsc?pia ?tica e eletr?nica, difra??o de raios x, satura??o
magn?tica e coercitividade, dureza, ataque qu?mico eletrol?tico. Foi realizado c?lculos das
sec??es verticais dos diagramas de fase para o sistema WC-FeNi com adi??o de cromo.
Os resultados obtidos e discutidos demonstram que o ligante 316L n?o ? uma alternativa
viav?l em metal duro devido conter elevado teor de cromo. O ligante alternativo 316L
quando sinterizado com carbeto de tungst?nio sempre precipitar? fase eta, fato que
inviabiliza sua aplica??o como ligante alternativo em WC. Para o ligante FeNi com adi??o
de cromo, os resultados demonstram que o m?ximo teor de cromo que pode estar contido
em solu??o em WC, de forma que n?o haja precipita??o de carbeto de cromo ? de
aproximadamente 4%. A adi??o de cromo acima de 4% em solu??o, leva ? precipita??o
de carbetos complexos de cromo, e ainda reduz drasticamente a janela de carbono do
comp?sito. / Hard metal WC-Co is used in the machining, drilling and or manufacturing of cutting
tools. Currently, 70% of the cutting tools are WC-binder carbides. In production numbers,
approximately 40,000 MT of WC-binder tools have been produced worldwide since
2011. Today, more than 90% of all WC-binder production uses cobalt as the main binder.
The superiority of cobalt over other binders is linked to several factors, the main being
the width of the carbon window in the phase diagram. The search for alternative binders
that may at least partially replace cobalt is of extreme importance due to the scarcity and
price of cobalt and especially the WC-Co system being carcinogenic. The goal of this
doctoral thesis was to analyze the feasibility of using alternatives binders 316L stainless
steel and FeNiCr alloy, in tungsten carbide. Both system WC-316L (5, 7 and 20% of
binder contents) and WC-20%FeNi with addition of chromium (in 5, 10 and 20% in
solution) were processed by powder metallurgy route following the steps: preparation of
the mixtures, milling (1h, 24h), compaction uniaxial (200MPa) and vacuum sintering
(1400oC/1h). The all samples were characterized by optical and electron microscopy, xray
diffraction, magnetic saturation and coercivity, hardness and electrolytic etching. The
calculation of vertical sections of the phase diagrams for the system WC-FeNiCr was
made. The results obtained and discussed demonstrate that the binder 316L, is not a viable
alternative in hard metal because it contains high chromium content. The binder 316L
when sintered with tungsten carbide will always precipitate eta phase, which makes its
application as an alternative binder in WC impossible. For the binder FeNiCr, the results
demonstrate that the maximum content of chromium that may be contained in solution in
tungsten carbide that there is no precipitation of chromium carbide is approximately 4%.
The addition of chromium above 4% in solution leads to the precipitation of chromium
complex carbides, and further drastically reduces the carbon window of the composite.
| Identifer | oai:union.ndltd.org:IBICT/oai:repositorio.ufrn.br:123456789/24639 |
| Date | 11 October 2017 |
| Creators | Santos, Alessandra Agna Ara?jo dos |
| Contributors | 05012180410, Silva, Angelus Giuseppe Pereira da, 30814111491, Silva, Ariadne de Souza, 00735940401, Silva, Gilson Garcia da, 56634161453, Manuel, Jo?o Baptista, 63728460478, Gomes, Uilame Umbelino |
| Publisher | PROGRAMA DE P?S-GRADUA??O EM CI?NCIA E ENGENHARIA DE MATERIAIS, UFRN, Brasil |
| Source Sets | IBICT Brazilian ETDs |
| Language | Portuguese |
| Detected Language | English |
| Type | info:eu-repo/semantics/publishedVersion, info:eu-repo/semantics/doctoralThesis |
| 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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