Banca de DEFESA: ROBERTA ARAUJO CAVALCANTE DE MENEZES
Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.STUDENT : ROBERTA ARAUJO CAVALCANTE DE MENEZES
DATE: 29/01/2022
TIME: 08:00
LOCAL: SalaVirtual
TITLE:
Study of the effect of niobium oxide addition on the microstructure and properties of the eurofer steel processed through powder metallurgy
KEY WORDS:
Keywords: EUROFER, Nb2O5, Powder Metallurgy, High Energy Milling, Sintering.
PAGES: 90
BIG AREA: Engenharias
AREA: Engenharia de Materiais e Metalúrgica
SUBÁREA: Metalurgia de Transformação
SPECIALTY: Metalurgia de Pó
SUMMARY:
ABSTRACT
EUROFER is a reduced activity ferritic-martensitic (RAFM) structural steel used for the construction of nuclear fusion reactors. However, when used at temperatures above 500 ºC, this material presents flaws mainly due to creeping and swelling. In this context, studies were developed to solve this problem without compromising the properties already acquired. The solution found was yttrium oxide dispersion strengthened (ODS). Pure EUROFER alloys and innovative EUROFER-ODS composites, obtained from EUROFER chips and niobium pentoxide (Nb2O5), were processed and developed by powder metallurgy (PM) in this work. The manufacturing processes used for obtaining EUROFER powder were also innovative for this steel, as it uses a green route, within mechanisms of self-sustainability and reuse of this material. The pure EUROFER chips were milled in a high energy ball miller (HEM), being studied at different times (5h, 10h, and 15h), and with the addition of Nb2O5(0% w., 3% w., 5% w. and 7 % w.) at the same time intervals. The powders were sintered via Spark Plasma Sintering (SPS) and Conventional Furnace (CF). The effect of varying the milling time and Nb2O5concentration, in addition to the sintering methods, on the physical, mechanical, electrical, and magnetic properties of the sintered materials were analyzed. The results have shown that, increasing the milling time, has reduced the average particle size distribution by 57%, improving the sinterability of the milled powders. XRD analyzes suggested the formation of martensite and austenite phases retained in the sintered samples obtained via SPS. The microhardness of the alloys obtained from pure EUROFER chips sintered by SPS (≈ 560 HV), were superior to those sintered by CF (≈ 65 HV) and the raw material's (410 HV). The addition of Nb2O5 in the EUROFER-ODS alloy maintained the microhardness of the SPS sintered samples in the same proportion of the raw material. However, the CF sintered samples showed lower microhardness values (≈ 78 HV). Furthermore, the densities of samples sintered via SPS were higher than those sintered via CF. Therefore, the results have showed that this new manufacturing method for the raw material is promising for the development of these new materials.
BANKING MEMBERS:
Interno - 1350249 - RUBENS MARIBONDO DO NASCIMENTO
Interno - 345842 - UILAME UMBELINO GOMES
Externo ao Programa - 350830 - JOSE HUMBERTO DE ARAUJO
Externo à Instituição - ANGELUS GIUSEPPE PEREIRA DA SILVA - UENF
Externa à Instituição - MARIA JOSÉ SANTOS LIMA - UFRN