Banca de QUALIFICAÇÃO: CLEBER DA SILVA LOURENÇO

Uma banca de QUALIFICAÇÃO de DOUTORADO foi cadastrada pelo programa.
STUDENT : CLEBER DA SILVA LOURENÇO
DATE: 30/01/2023
TIME: 13:30
LOCAL: Remoto
TITLE:

Partial replacement of the Co ligand by Nb in carbide (WC-(10-X)%pC0%XpNb (X=0; X=2.5; X=5)) prepared via HEBM and sintered in high vacuum and by plasma pulse


KEY WORDS:

carbide, binder, partial replacement, high energy ball milling and sintering


PAGES: 90
BIG AREA: Engenharias
AREA: Engenharia de Materiais e Metalúrgica
SUBÁREA: Metalurgia de Transformação
SPECIALTY: Metalurgia de Pó
SUMMARY:

Carbide is a material widely used in various applications such as turning, milling and drilling. The carbide most used is made up of a major hard phase of WC and a minor metallic binder of Co, normally less than 25% by mass. However, although the use of Co as a binder results in better mechanical properties than cemented carbide, the scientific community has been looking for a partial or total substitute for this binder due to its toxicity and scarcity. As a result, this research seeks to evaluate the possibility of a partial replacement of Co by Nb. For this purpose, composite powders of WC-10%pCo, WC-2.5%pNb7.5%pCo and WC-5%pNb5%pCo were prepared by high-energy grinding (HEM) in a wet medium for 2, 15 and 30 hours. The milled powders were compacted at 250 MPa and subsequently sintered in a conventional resistive furnace at 1450 °C and 1550 °C. The powders processed through HEBM for 30 hours were also sintered by two different routes that make it possible to obtain carbide with better properties. For the first route, the milled powders were compacted to 250 MPa and sintered in high vacuum (10-4 toor) at a temperature of 1550 °C. The second route was the plasma pulse sintering (SPS) process at a temperature of 1300 °C. The starting powders, milled and sintered samples were characterized by scanning electron microscopy (SEM-FEG), x-ray diffraction (XRD), energy dispersive spectroscopy (EDS) and the powders were also characterized by measurements of particle size analysis. The density of the sintered samples was determined by the Archimedes method. Also, the Vickers microhardness was measured in the sintered samples. The results revealed that the HEBM process is efficient to promote the phase homogenization process and reduce the particle size, favoring the sintering process of the composite powders. The SPS technique of milled powders for 30 hours proved to be more efficient in enabling the partial replacement of Co by Nb, leading to obtaining a relative density of 84.23% for the cemented carbide of WC-5%Co5% Nb.


COMMITTEE MEMBERS:
Presidente - 345842 - UILAME UMBELINO GOMES
Externa à Instituição - ARIADNE DE SOUZA SILVA
Externa à Instituição - MARIA JOSÉ SANTOS LIMA
Externo à Instituição - NAILTON TORRES CAMARA
Notícia cadastrada em: 25/01/2023 12:03
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