Abstracts Book - IMRC 2018

• SD7-O001 Invited Talk
ELECTRON MICROSCOPY CHARACTERIZATION OF SUPERDUPLEX
STAINLESS STEEL 2507 WITH FRAGILIZATION THERMAL
TREATMENT
Alberto Ruiz 1 , Victor Sayil López Álvarez 1 , Gildardo Gutiérrez Vargas 1 , Reyes-Gasga Jose 2
1 Universidad Michoacana de San Nicolás de Hidalgo, Instituto de Investigación en Metalurgia y
Materiales, Mexico. 2 Universidad Nacional Autónoma de México, Instituto de Física, Mexico.
Stainless steels are iron-based alloys with more than 10.5% wt of chromium. The
chromium amount in these alloys is important because it causes good corrosion
resistance due to the thin film of chromium oxide (Cr 2 O 3 ) produced in oxidizing
environments. Stainless steels with around 30 %wt of chromium are named
super duplex. The main limitation of duplex stainless steels for application in the
industry is the embrittlement they present when working inside extreme
environments or exposed to temperatures between 280 and 500 ºC.
Fragilization occurs mainly in the ferrite phase (α phase) due to the spinodal
decomposition in alloys with a high chromium content.
The structural and chemical analysis of super duplex steel UNS S32750 (SAF
2507) by electronic diffraction and electron microscopy is presented in this work.
The chemical analysis was performed by characteristic x-ray spectroscopy (EDS)
and x-ray diffraction. In addition to the sample worked at room temperature
(control sample), the samples were subjected to an ex-situ thermal treatment of
aging at 475 °C, which modified their mechanical properties and microstructure
through embrittlement. The samples were hold at this temperature for 300 h
and 1000 h, respectively.
The internal structure of the steel grains is of ferrite and austenite phases. A
high density of dislocations was observed in the control sample, which
decreased after the thermal treatment. In the 300 h and 1000 h samples the
results indicate a significant change in the microstructure of the steel, mainly in
the ferrite phase, where the secondary phase alfa prima (α) is precipitated.
Depending on the residence time at 475 °C, the shape of precipitates changes
spherical to needle.
Acknowledgment:
We thank to M. Sc. J. A. Rodríguez Torres and Eng. Francisco Solorio IIMM-
UMSNH, and Dr. S. Tehuacanero-Cuapa, Eng. S. Tehuacanero Nuñez and Mr.