Estudo da microestrutura dos aços inoxidáveis austeníticos AISI 316L e 317L soldados pelo processo TIG
Tipo
Dissertação
Data de publicação
2019-02-01
Periódico
Citações (Scopus)
Autores
Pereira, Karla Guimarães Santos
Orientador
Terence, Mauro César
Título da Revista
ISSN da Revista
Título de Volume
Membros da banca
Massi, Marcos
Monteiro, Waldemar Alfredo
Monteiro, Waldemar Alfredo
Programa
Engenharia de Materiais e Nanotecnologia
Resumo
Stainless steels were developed in the beginning of the 20th century and have been constantly
improved since then. As other metal alloys, stainless steels are classified according to the
chemical composition Austenitic stainless steels represent 2/3 of the world's stainless steel
production due to their resistance to corrosion, oxidation, hot mechanical strength, workability
and weldability. These properties are obtained by the addition of different alloying elements.
In industry, the welding process is one of the most applied in austenitic stainless steels. Both
the alloying elements and the different processes have a direct influence on the microstructure
of the steel. The austenitic stainless steels present predominantly austenitic microstructure, but
during solidification this structure is altered due to the formation of delta ferrite, derived from
the segregation of stabilizing elements of the ferrite. The quantification of delta ferrite is
extremely important for properties related to ductility, crack susceptibility and mechanical
resistance. In addition, intermetallic phases, such as sigma, precipitates from the delta ferrite .
There are several types of reagents used to perform chemical / electrolytic etching to reveal
these phases in the microstructure. This work studied a methodology for the microstructural
characterization of AISI 316L and AISI 317L austenitic alloys, welded by the GTAW process
and submitted to heat treatments with different times, in order to reveal δ ferrite and
intermetallic phases, sigma ( σ), chi (χ) and the Laves phase (η). AISI 316L and AISI 317L
alloys were selected because they are characteristics for applications requiring high corrosion
resistance. Both AISI 316L and AISI 317L alloys were solubilized at 1080 ° C with different
times. Samples of both materials were analyzed in the base metal and in the weld metal, in the
condition of welding and without heat treatment. According to Vander Voort electrolytic
etching using the reactants in the proportions: 10% of oxalic acid, 10% KOH and 20% NaOH,
all subjected to a voltage of 6V for 60s, reveal ferrite δ and some intermetallic phases such as
sigma phase. In addition, a study on pitting corrosion was carried out by the potentiodynamic
cyclic polarization method. It was concluded as well as the bibliographical references that the
presence of intermetallic phases directly affects the resistance to pitting corrosion. The samples
without heat treatment presented higher percentage of delta ferrite and were more resistant to
pitting corrosion.
Descrição
Palavras-chave
corrosão por pite , fases intermetálicas , aço inoxidável
Assuntos Scopus
Citação
PEREIRA, Karla Guimarães Santos. Estudo da microestrutura dos aços inoxidáveis austeníticos AISI 316L e 317L soldados pelo processo TIG. 2019. 151 f. Dissertação (Mestrado em Engenharia de Materiais e Nanotecnologia) - Universidade Presbiteriana Mackenzie, São Paulo.