doctoralThesis
Estudo da microestrutura e das propriedades do metal duro WC- (Fe-Nb/NbH-C) obtido por moagem de alta energia e spark plasma sintering
Fecha
2022-05-16Registro en:
TAVARES, Matheus de Medeiros. Estudo da microestrutura e das propriedades do metal duro WC- (Fe-Nb/NbH-C) obtido por moagem de alta energia e spark plasma sintering. 2022. 89f. Tese (Doutorado em Ciência e Engenharia de Materiais) - Centro de Ciências Exatas e da Terra, Universidade Federal do Rio Grande do Norte, Natal, 2022.
Autor
Tavares, Matheus de Medeiros
Resumen
The search for alternative binders for hardmetals, also called cemented carbides, has
moved the scientific community. Alternative Fe-based binders have been widely studied
and used in selected applications. An unprecedented addition to this ligand would be the
use of niobium, a metal of high global interest, few explored and abundant in Brazilian
territory. This work aims to investigate the properties of the Fe-Nb/NbH-C system, using
it as an alternative binder to produce WC-(Fe-Nb/NbH-C) cemented carbides. For this
purpose, high energy ring and planetary milling techniques were used, using controlled
atmosphere sintering and spark plasma sintering (SPS) techniques in a sintering
temperature range from 1150ºC to 1450ºC. To evaluate the composition, microstructure
and properties, the ThermoCalc software was used, in addition to the XRD, MO, SEM,
WDS, density, Vickers hardness and fracture toughness techniques. The preliminary
results pointed to planetary mill as the most efficient method for homogenization and
particle size reduction, resulting in samples with better mechanical properties. Controlled
atmosphere sintering for this application proved to be unfeasible, on the other hand, spark
plasma sintering proved to be an efficient method for the production of densified samples.
The sintering temperature of 1250ºC provided the best microstructure and properties
results for all SPS processing conditions. Replacing Nb for NbH, it was possible to obtain
samples with more homogeneous and densified microstructure by reducing the size of the
niobium particles, absence of eta phase, and a remarkable microstructural gradient
formation, as well as hardness values of up to 1620Hv, meaning an increase of
approximately 15% in relation to pure niobium compositions.