Banca de DEFESA: CLEBER DA SILVA LOURENÇO

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
STUDENT : CLEBER DA SILVA LOURENÇO
DATE: 25/09/2023
TIME: 08:00
LOCAL: Sala Virtual
TITLE:

 

Study of the partial substitution of the Co binder with Nb in hard metal  prepared via HEM and sintered in conventional furnace, high vacuum, and spark plasma sintering (SPS)



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:

Hard metal, also known as cemented carbide, is a widely used material in various applications such as turning, milling, and drilling. The most commonly used hard metal consists of a major hard phase of WC (tungsten carbide) and a minor metallic binder phase of Co (cobalt), usually making up less than 25% by mass. However, although the use of Co as a binder results in improved mechanical properties for the cemented carbide, the scientific community has been seeking a partial or complete substitute for this binder due to its toxicity and scarcity. In light of this, this research aimed to evaluate the possibility of partially replacing Co with Nb (niobium). For this purpose, composite powders of WC-10%Co, WC-2.5%Nb-7.5%Co, and WC-5%Nb-5%Co were prepared using wet high-energy milling (HEM) 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 via 30-hour WHEM were also sintered using two distinct routes to achieve better properties for the hard metal. In the first route, the milled powders were compacted at 250 MPa and sintered in high vacuum (10-4 torr) at a temperature of 1550°C. In the second route, the powders were sintered using spark plasma sintering (SPS) at a temperature of 1300°C. The starting powders, milled powders, and sintered samples were characterized using field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), and energy-dispersive spectroscopy (EDS). Particle size distribution measurements were also conducted for the powders. The density of the sintered samples was determined using the Archimedes' method. Additionally, Vickers microhardness measurements were carried out on the sintered samples. The results revealed that the HEM process efficiently promotes phase homogenization and particle size reduction,  facilitating the sintering process of the composite powders. The SPS technique for the 30-hour milled powders proved to be more effective in enabling the partial substitution of Co with Nb, resulting in a relative density of 84.23% for the cemented carbide WC-5%Co-5%Nb.

 

COMMITTEE MEMBERS:
Presidente - 345842 - UILAME UMBELINO GOMES
Interna - 3352345 - MARIA JOSE SANTOS LIMA
Externo ao Programa - 1674707 - MARCO ANTONIO MORALES TORRES - UFRNExterna à Instituição - ARIADNE DE SOUZA SILVA
Externo à Instituição - NAILTON TORRES CAMARA - IFRN
Externo à Instituição - RAFAEL ALEXANDRE RAIMUNDO - UFPB
Notícia cadastrada em: 25/08/2023 10:46
SIGAA | Superintendência de Tecnologia da Informação - (84) 3342 2210 | Copyright © 2006-2024 - UFRN - sigaa13-producao.info.ufrn.br.sigaa13-producao