Banca de DEFESA: EMANOELA PEREIRA DE MATTOS

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
DISCENTE : EMANOELA PEREIRA DE MATTOS
DATA : 25/08/2017
HORA: 09:00
LOCAL: Sala de reuniões do DEMat
TÍTULO:

HIGH TEMPERATURE BRAZING OF LEAN DUPLEX AND DUPLEX STAINLESS STEELS WITH AMORPHOUS NICKEL-BASED FOILS

PALAVRAS-CHAVES:

High temperature brazing, Ni-based amorphous foils, Austenitic stainless steel, Duplex stainless steel, Lean duplex stainless steel, Intermetallics.

PÁGINAS: 140
GRANDE ÁREA: Engenharias
ÁREA: Engenharia de Materiais e Metalúrgica
RESUMO:

Duplex stainless steels, characterized by biphasic microstructure composed of similar fractions of ferrite and austenite, have been expanding their application in several fields, to the detriment of the use of traditional austenitic and ferritic stainless steels, in particular in the chemical and petrochemical industries where they can advantageously meet the requirements of mechanical resistance and corrosion in aggressive media. For fabrication of components with complex geometries and / or with reduced thickness sheets the most indicated processes are solid state diffusion welding and high temperature brazing (BAT) over conventional fusion welding methods. In this context, this work initially describes the results of BAT tests on austenitic stainless steel AISI 316L, exploring the applicability of this technology as an alternative manufacturing route for compact heat exchangers.. In addition, as main objective of the work were evaluated in more detail different brazing systems formed by 3 duplex stainless steels and 5 different nickel-based addition alloys. As base metals were used plates of duplex stainless steels UNS S32101 and UNS S32304 and duplex UNS S32205 and as addition metals, amorphous nickel-based foils with different amounts of alloying elements such as Cr, Fe and in particular the Si metalloids , B, P and C. The brazing process was carried out in a high vacuum atmosphere (10-4 mbar), under temperatures of 1020, 1100 and 1160 ° C for times of 30 minutes and 1 hour. A wedge brazing test at 1020 ° C with subsequent heat treatment (1000 and 1100 ° C for 60 and 120 minutes) was performed for the lean duplex UNS S32101 steel with addition alloy containing P in order to determine the behavior of intermetallics in the joint. The characterization of the brazed joints for the microstructural integrity of the steels, the presence of intermetallic phases in the melting zone and the base metal / metal addition interface was performed by optical microscopy, field emission scanning electron microscopy, dispersive energy spectroscopy, backscattered electron diffraction, X-ray diffraction and Vickers microhardness. The best-performing addition metal is the Si-B addition alloy, with continuous γ-Ni phase brazing and dispersed precipitation of borides and nitrides in the brazing zone. The lean duplex stainless steel UNS S32101 showed a phenomenon of high ferritic grain growth under vacuum at temperature over 1100 C, both on the free surface and at the brazing interface. The influence of the brazing atmosphere on the loss by sublimation of Mn and N, as well as the B content in the occurrence of this effect is discussed.

MEMBROS DA BANCA:
Presidente - 2156996 - AUGUSTO JOSE DE ALMEIDA BUSCHINELLI
Interno - 1350249 - RUBENS MARIBONDO DO NASCIMENTO
Externo ao Programa - 1938946 - NICOLAU APOENA CASTRO
Externo à Instituição - ALOISIO NELMO KLEIN - UFSC
Externo à Instituição - WANDERSON SANTANA DA SILVA - UFSC