Título: | EFFECTS OF PRECIPITATION PROCESSES INDUCED BY ORDERING REACTIONS IN A NICKEL BASE SUPERALLOY (59-23 CR-16 MO) | |||||||
Autor: |
ERIKA SANTANA MOTA NICOLETTI |
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Colaborador(es): |
FATHI AREF IBRAHIM DARWISH - Orientador IVAN GUILLERMO SOLORZANO NARANJO - Coorientador |
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Catalogação: | 29/JUN/2004 | Língua(s): | PORTUGUESE - BRAZIL |
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Tipo: | TEXT | Subtipo: | THESIS | |||||
Notas: |
[pt] Todos os dados constantes dos documentos são de inteira responsabilidade de seus autores. Os dados utilizados nas descrições dos documentos estão em conformidade com os sistemas da administração da PUC-Rio. [en] All data contained in the documents are the sole responsibility of the authors. The data used in the descriptions of the documents are in conformity with the systems of the administration of PUC-Rio. |
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Referência(s): |
[pt] https://www.maxwell.vrac.puc-rio.br/projetosEspeciais/ETDs/consultas/conteudo.php?strSecao=resultado&nrSeq=5105&idi=1 [en] https://www.maxwell.vrac.puc-rio.br/projetosEspeciais/ETDs/consultas/conteudo.php?strSecao=resultado&nrSeq=5105&idi=2 |
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DOI: | https://doi.org/10.17771/PUCRio.acad.5105 | |||||||
Resumo: | ||||||||
The nickel base superalloy, 59-23Cr-16Mo, was developed in
the nineties and has since been used in chemical and
petrochemical industries as well as in equipment for
environmental control. The alloy has, occasionally, been
presenting problems of pit corrosion in the heat affected
zones (HAZ) of welded joints. With the purpose of
elucidating the mechanisms associated with precipitation
processes, specimens were taken from the as-received alloy
and submitted to isothermal aging at two different
temperatures of 700 and 900oC, for time intervals varying
from 1 to 100 hours. A study of the microstructural
evolution accompanying the aging treatment was then
conducted by means of X-ray diffraction, optical and
scanning electron microscopies, making use of the energy
dispersion spectroscopy (EDS) and electron back scattering
diffraction (EBSD) techniques. Conventional and high
resolution electron microscopies were also used as
additional tools in order to follow the nanoescale
precipitation processes. The mechanical behavior of the
alloy in its different microstructural conditions was
evaluated by means of uniaxial tensile tests as well as by
microhardness measurements. Variations in electrical
resistivity accompanying microstructure evolution were
followed and electrical resistivity of a TIG welded joint
was mapped. The results obtained have indicated the
presence of {1, 1/2, 0} reflections in the diffraction
patterns of the majority of the microstructures in
question. Such reflections, which are typical of short
range ordered (SRO) state, indicate that the alloy is prone
to precipitation mechanisms via ordering reactions,
involving atomic stacking on {4,2,0} planes. A large
population of nanoprecipitates, referring to the Ni2(Mo,Cr)
phase, was detected in all of the microstructural
conditions considered in this work. In addition, the aged
specimens were also found to contain microscale Ni2(Mo,Cr)2
particles formed at the grain boundaries via ordering
reactions occurring preferentially in the grain boundary
area. The mechanical behavior of the aged alloy is strongly
related to the precipitation of this microscale phase,
which governs the ductility level as well as the transition
in the fracture mode from intragranular to intergranular.
Finally, the electrical resistivity variation within the
HAZ was not associated with microstrutural alterations and
therefore was attributed to variations in the quantity
of the short range ordered structures.
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