Microsegregation and Precipitates in Inconel 625 Arc Weld Overlay Coatings on Boiler Pipes / Mikrosegregacja I Wydzielenia W Powłokach Ze Stopu Inconel 625 Napawanych Łukowo Na Rury Kotłowe

The aim of this work was to investigate the microsegregation and precipitates formed due to segregation in Inconel 625 arc weld overlay coatings on boiler pipes. Examination of microsegregation and precipitates were carried out by means of a scanning electron microscope (SEM) equipped with an EDS de...

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Bibliographic Details
Published in:Archives of metallurgy and materials 2015-12, Vol.60 (4), p.2599-2606
Main Authors: Rozmus-Górnikowska, M., Blicharski, M.
Format: Article
Language:English
Subjects:
Alloy solidification
Boilers
Carbon nitride
Chromium
Coatings
Corrosion
Dissolution
Electrolytic dissolution
Heat treating
Inconel 625
Investigations
Iron
Laves phase
microsegregation
Molybdenum
Nickel base alloys
Niobium
Pipes
Precipitates
SEM
Solid solutions
Solidification
Solids
Solution strengthening
STEM
Superalloys
TEM
weld overlay
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Summary:The aim of this work was to investigate the microsegregation and precipitates formed due to segregation in Inconel 625 arc weld overlay coatings on boiler pipes. Examination of microsegregation and precipitates were carried out by means of a scanning electron microscope (SEM) equipped with an EDS detector as well as a transmission electron microscope (TEM) equipped with a HAADF (STEM) and an EDS detectors. The presence of precipitations in the weld overlay was also confirmed with X-ray diffraction analysis (XRD) of residue in the form of powder that remained after the electrolytic dissolution of weld overlay matrix. The investigations showed that the interdendritic regions were considerably enriched during microsegregation with Nb, and less so with Mo. The distribution of Cr and Fe in the weld overlay is relatively uniform. The value of the partition coefficient k for Mo and Nb is lower than 1. Therefore, these elements segregate during solidification into the liquid and, once solidification is finished, the interdendritic regions are considerably enriched with these elements. The value of k for Cr, Ni and Fe are only slightly higher than 1. Though the Inconel 625 is a solid-solution strengthened alloy, precipitation of secondary phases occurs in weld overlays. Precipitations were identified as a Laves phase and carbonitrides (Nb, Ti)(C, N).
ISSN:2300-1909
1733-3490
2300-1909
DOI:10.1515/amm-2015-0420