Banca de QUALIFICAÇÃO: ROBERTA ARAUJO CAVALCANTE DE MENEZES

Uma banca de QUALIFICAÇÃO de DOUTORADO foi cadastrada pelo programa.
STUDENT : ROBERTA ARAUJO CAVALCANTE DE MENEZES
DATE: 30/09/2021
TIME: 13:00
LOCAL: Sala Virtual
TITLE:

Estudo do efeito da adição de pentóxido de nióbio na microestrutura e propriedades do aço EUROFER processado pela metalurgia do pó

Stud 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, Recycling, 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:

EUROFER is a structural material used in the construction of the ITER nuclear fusion reactor, as it has several properties that make it attractive for this application. However, this material has failures due to creep and swelling when used in temperatures above 500 ºC. Studies were developed to overcome this problem, without harming the properties harm the properties already acquired. The solution found was include the use of hardening by yttrium oxide dispersion hardening (ODS). It is also known that the EUREFER components used in ITER are often manufactured through machining processes, which results in significant chip residue generation. At the same time, interest in studying new chip recycling techniques has been growing in recent years. In this work, pure EUROFER and composite EUROFER-ODS alloys manufactured from EUROFER chip (machinery waste) were analyzed. The behavior of the EUROFER-ODS alloy was also analyzed when niobium pentoxide (Nb₂O₅) was added to steel through powder metallurgy (PM).The EUROFER chips were milled in a high-energy ball mill (HEM) under different times (5h, 10h, and 15h), with the addition of Nb₂O₅ (0%_w., 3%_w., 5%_w. e 7%_w.). Then, they powders were sintered via Spark Plasma Sintering (SPS) and conventional resistive furnace (CRF). The effect of milling times, Nb₂O₅ concentration, and sintering methods were analyzed on the physical, mechanical, and electrical properties of the sintered materials. The results showed that increasing the milling time reduced the average particle size distribution by 57% and improved the sinterability of the milled powders. XRD analyzes suggest the formation of phases like martensite and austenite retained in the sintered via SPS. The microhardness of the alloys obtained from pure EUROFER chips sintered by SPS (≈ 560 HV), were superior to those sintered by CRF (≈ 65 HV) and from the bar as received (410 HV). The addition of Nb₂O₅ in the EUROFER-ODS alloy kept the microhardness of samples sintered via SPS in the same order of magnitude of the bar, but those sintered via FRC had lower values (≈ 78 HV). Furthermore, the densities of samples sintered via SPS were higher than those sintered via CRF. Finally, the general results suggest the powder metallurgy can be an alternative to EUROFER steel chip recycling.

BANKING MEMBERS:
Presidente - 345842 - UILAME UMBELINO GOMES
Interno - 1350249 - RUBENS MARIBONDO DO NASCIMENTO
Externo à Instituição - MARCELLO FILGUEIRA - UENF
Externa à Instituição - MARIA JOSÉ SANTOS LIMA - UFRN