Banca de DEFESA: ALESSANDRA AGNA ARAÚJO DOS SANTOS

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
DISCENTE : ALESSANDRA AGNA ARAÚJO DOS SANTOS
DATA : 19/10/2017
HORA: 13:30
LOCAL: Sala de aulas do PPGCEM
TÍTULO:

STUDY OF THE SINTERING OF TUNGSTEN CARBIDE USING ALTERNATIVES BINDERS 316L AND FeNi WITH CROMIUM ADDED

PALAVRAS-CHAVES:

Powder metallurgy, hard metal, alternative binders, 316L, FeNi, eta phase, chromium carbide.

PÁGINAS: 128
GRANDE ÁREA: Engenharias
ÁREA: Engenharia de Materiais e Metalúrgica
RESUMO:

Hard metal WC-Co is used in machining, drilling or in the manufacture of cutting tools. Nowadays, 70% of the cutting tools are WC-binder. In production numbers, approximately 40.000 MT tools of WC-binder have been produced worldwide since 2011. Today, more than 90% of all WC-binder uses cobalt as the main binder. The superiority of cobalt in relation to other binders is related to several factors, the main being the width of the carbon window. However, it has been studied for decades by alternative binders due to the scarcity and price of cobalt and mainly by the system WCCo be carcinogenic. The goal of this doctoral thesis was to analyze the sintering of the tungsten carbide with alternative binders (steel 316L, and FeNi with addition of chromium content) and verify if they are viable. Both systems WC-316L (binder content of 5, 7 and 20%) and WC-20%FeNi with addition of chromium (chromium content were added in 0, 5, 10 and 20%) were processed by the Powder Metallurgy, following the steps: preparing of the powders, milling (1h, 24h), isostatic compaction (200 MPa) and vacuum sintering (1400oC/1h). The characterization performed in all the sintered samples were: optical and electron microscopy, x-ray diffraction, magnetic saturation and coercivity, hardness, electrochemical etching, and calculation of the vertical sections of the phase diagrams for the system WC-FeNi with addition of chromium. The results obtained and discussed demonstrate that the binder 316L in hard metal is not a viable, because of the high chromium content in this alloy, that forming complex carbides which weaken the structure. The steel 316L binder in hard metal, regardless of the binder content or carbon content, precipitate eta phase (phase that must be avoided in hard metal). For the FeNi binder with addition of chromium, the results demonstrate that the maximum content of chromium that may be contained in solution is approximately 4% (for a binder content of 20%), FeNi with chromium content above 4% will be precipitated eta phase and other stable chromium carbides, the chromium content above 4% will still drastically reduces the carbon window of the composite, making it practically impossible to avoid eta phase or graphite precipitation.

MEMBROS DA BANCA:
Externo à Instituição - ANGELUS GIUSEPPE PEREIRA DA SILVA - UENF
Externo à Instituição - GILSON GARCIA DA SILVA - IFRN
Externo à Instituição - JOAO BAPTISTA MANUEL - UFRPE
Interno - 1350249 - RUBENS MARIBONDO DO NASCIMENTO
Presidente - 345842 - UILAME UMBELINO GOMES