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).
 M. Montgomery, A.N. Hansson, S.A. Jensen, T. Vilhelmsen, N.H. Nielsen, Materials and Corrosion 62, 1-12 (2011).
 J.N. DuPont, J.C. Lippold, S.D Liser, Welding metallurgy and weldability nickel base alloys, A John Wiley & Sons, INC., Publication, 2009.
 J.F. Lancaster, Metallurgy of welding, Abington Publishing, Cambridge 1999.
 S. Kou, Welding Metallurgy, A John Wiley & Sons, INC., Publication, New Jersey 2003.
 H.R. Zareie Rajani, S.A.A. Akbari Mousavi, F. Madani Sani, Materials and Design 43, 467-474 (2013).
 J.N. DuPont, A. W. Stockdale, A. Caizza, A. Esposito, Welding Journal 92, 218-225 (2013).
 S.W. Banovic, J.N. DuPont, A.R. Marder, Science and Technology of welding and Joining 7, 374-383 (2002).
 M.J. Cieslak. T.J. Headley, T Kollie, A.D. Romig, Metallurgical Transactions A 19A, 1988-2319 (1987).
 M. Rozmus-Górnikowska, M. Blicharski, J. Kusiński, L. Kusiński, M. Marszycki, Archives of Metallurgy 58, 1093-1096 (2013).
 M. Rozmus-Górnikowska, M. Blicharski, J. Kusiński, Metallic Materials 52, 141-147 (2014).
 M.J. Cieslak, T.J. Headley, R.B. Frank, Welding Research Supplement, 473-482 (1989).
 M.J. Cieslak, The metallurgy of alloy 625. Superalloys 718, 625 and Various Derivatives, The Minerals, Metals and Materials Society, Pennsylvania 1991.
 M.J. Cieslak, Welding Research Supplement, 49-56 (1987).
 J.N. DuPont, Metallurgical and Materials Transactions A. 27A, 3612-3620 (1996).
 J.N. DuPont, S.W. Banovic, A.R. Marder, Supplement to the Welding Journal, 125-135 (2003).
 J.N. DuPont, C.V Robino, A.R. Marder, M.R. Notis, Metallurgical and Materials Transactions A. 29A, 2797-2805 (1998).
 C.C Silva, H.C. de Miranda, M.F. Motta, J.P Farias, C.R.M. Afonso, A.J. Ramires, Journal of Materials Research and Technology 2, 228-237 (2013).
 S. Floreen, G.E. Fuschs, W.J. Yang, The metallurgy of alloy 625. Superalloys 718, 625 and Various Derivatives, The Minerals, Metals and Materials Society, Pennsylvania 1991.
 J.N. DuPont, C.V Robino, J.R. Michael, M.R. Notis, A.R. Marder, Metallurgical and Materials Transactions A. 29A, 2785-2796 (1998).
 F. Cortial, J. M. Corrieu, Ch. Vernot-Loier, Heat treatments of weld alloy 625: influence on the microstructure, mechanical properties and corrosion resistance, Superalloys 718, 625 and Various Derivatives. The Minerals, Metals and Materials Society, Pennsylvania (1994).
 M.C. Maguire, J.R. Michael, Weldability of alloy 718, 625 and variants. Superalloys 718, 625 and Various Derivatives, The Minerals, Metals and Materials Society, Pennsylvania (1994).
 M. Rozmus-Górnikowska, Ł. Cieniek, M. Blicharski, J. Kusiński, Archives of Metallurgy 59, 1081-1084 (2014).