Banca de DEFESA: LUCAS OLIVEIRA SIQUEIRA

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : LUCAS OLIVEIRA SIQUEIRA
DATE: 23/08/2021
TIME: 09:00
LOCAL: Defesa por videoconferência
TITLE:

Brazing of austenitic stainless steel using silver-based filler metals applied to high-pressurized pipes in aircrafts

KEY WORDS:

Oxyacetylene torch brazing; Silver-based filler metal; Stainless steel; Graphene oxide; Microstructural evaluation; Mechanical properties.

PAGES: 99
BIG AREA: Engenharias
AREA: Engenharia Aeroespacial
SUMMARY:

Currently, the transport of passengers on civil commercial aircraft is one of the most common and recurrent ways to travel long distances. However, this activity is carried out at high altitudes, a situation in which the amount of oxygen available in the air becomes insufficient for the maintenance of human action. From there, the aircraft are equipped with oxygen feed systems to supply the needs of this gas required by the lungs. The high-pressure pipes of this system are manufactured in stainless steel and commonly joined by brazing using silver-based filler metals, but studies in the literature about this joining are quite scarce. In this context, this research aims to contribute to the literature by providing relevant microstructural and mechanical information about the joining of 304 stainless steel by brazing with an oxyacetylene torch using silver-based metals with silver content of 25%, 35% and 45%. Furthermore, a new filler metal with low silver content (25%) with addition of graphene oxide is proposed. Visual inspection of the brazed joints indicated that surface preparation greatly affects the formation of cracks and pores in the filler metal region. The flame type test confirmed that the neutral type flame is best suited for brazing stainless steels using silver-based filler metal, providing a greater degree of fill of the brazed joint. The microstructural analysis revealed that the brazed joint with the addition of graphene oxide presented a more homogeneous and refined microstructure compared to the condition without addition of graphene oxide. Furthermore, a microstructural heterogeneity was verified in the brazed joints with 25% and 35% of silver. The Vickers microhardness tests were in agreement with the microstructural analyses, where the graphene oxide brazed joint presented a slightly higher hardness compared to all other filler metal conditions due to the refined microstructure.

BANKING MEMBERS:
Interna - 3100969 - NATHALIA BEZERRA DE LIMA
Externo à Instituição - SERGIO DE TRAGLIA AMANCIO FILHO
Interno - 1132272 - SEVERINO LEOPOLDINO URTIGA FILHO
Presidente - 2154866 - TIAGO FELIPE DE ABREU SANTOS