Weldability testing to understand composition effects on eutectic backfilling in Ni-30Cr alloys

  • R. A. WheelingEmail author
  • J. C. Lippold
Research Paper


Using Ni-30 wt% Cr in nuclear power reactors requires compatible fillers to ensure reliable welded joints. The high chromium content provides resistance to stress corrosion cracking (SCC), and niobium (Nb) additions have been made to Ni-30Cr filler metals to provide resistance to ductility dip cracking (DDC). Previous work suggested that increasing Nb from 2–4 to 6–8 wt% reduces cracking susceptibility due to crack healing supported by eutectic backfilling. Additional reduction in solidification cracking is realized when Mo additions are made in conjunction with the higher Nb levels. Based on qualitative evidence that the composition of the eutectic liquid changes grain boundary wetting characteristics and promotes backfilling, the current study was designed to quantify this behavior using a Varestraint-M test (adaptation of the original Varestraint test). The results suggest that when the Nb-rich eutectic also contains Mo, the liquid is more effective in wetting grain boundaries and promoting backfilling. This change in backfilling behavior is attributed to grain boundary wetting variability based on eutectic composition. A better fundamental understanding of the effect of Mo on grain boundary wetting of the Nb-rich eutectic phase will potentially facilitate the development of filler metals that rely on eutectic healing (or backfilling) to provide resistance to solidification cracking.


Alloy 690 Eutectic backfilling Crack healing Solidification cracking Ni-30Cr 



The lead author (RW) would like to thank the Graduate School at the Ohio State University for providing a fellowship during the first year of graduate studies and to the Department of Energy (DOE) Nuclear Engineering University Program (NEUP) for providing continuing support through an NEUP Fellowship. Fellow graduate students are recognized for discussion regarding guidance with experimental techniques. We also thank Ed Pfeiffer, support staff in the Welding Engineering Program at OSU, for his dedication and commitment to the development of a safe and sustainable research environment.


  1. 1.
    Kiser SD, Zhang R, Baker BA (2008) A new welding material for improved resistance to ductility dip cracking. Special Metals Welding Products Company and Huntington. Alloys/Special Metals Corporation, NC, USA and WV, USAGoogle Scholar
  2. 2.
    Lippold JC, Kiser SD, DuPont JN (2009) Welding metallurgy and weldability of nickel base alloys. Wiley, NobokenGoogle Scholar
  3. 3.
    McCracken S (2015) Dissimilar metal weld issues and repair strategies in the nuclear industry. Electric Power Research InstituteGoogle Scholar
  4. 4.
    Ramirez AJ, Sowards JW, Lippold JC (2006) Improving the ductility-dip cracking resistance of Ni-base alloys. J Mater Process Technol 179:212–218CrossRefGoogle Scholar
  5. 5.
    Bollinghaus T, Herald H, Cross C (2008) Hot cracking phenomena in welds II. Springer, BerlinCrossRefGoogle Scholar
  6. 6.
    Kazuyoski S, Bunda K, Ogiwara H, Nishimoto K (2012) Hot cracking susceptibility of commercial alloy 52 filler metals in multipass welding of alloy 690. In: DebRoy T, David SA, DuPont J et al (eds) Trends Weld. Res. Proc. 9th Int. Conf. ASM International, pp 322–329Google Scholar
  7. 7.
    Borland JC (1960) Generalized theory of super-solidus cracking in welds and castings. Br Weld J 7:508–512Google Scholar
  8. 8.
    Wheeling RA, Lippold JC (2016) Solidification cracking susceptibility of Ni-30Cr weld metals with variable niobium and molybdenum. Weld J 95:229–238sGoogle Scholar
  9. 9.
    Wheeling RA, Lippold JC (2016) Characterization of weld metal microstructure in a Ni-30Cr alloy with additions of niobium and molybdenum. Mater Charact 115. CrossRefGoogle Scholar
  10. 10.
    Lundin CD, Chou CPD, Sullivan CJ (1980) Hot cracking resistance of austenitic stainless steel weld metals increasing Mn and Mo content and avoiding multiple thermal cycles on. Weld Res Suppl:226s–232s. CrossRefGoogle Scholar
  11. 11.
    Wheeling RA, Lippold JC (2016) Effect of composition on grain boundary wetting characteristics in Ni-30Cr weld metal. Weld World 61:315–324. CrossRefGoogle Scholar
  12. 12.
    Savage WF, Lundin CD (1965) The Varestraint test. Weld J 44:433s–442sGoogle Scholar
  13. 13.
    Savage WF, Lundin CD (1966) Application of the Varestraint technique to the study of weldability. Weld J 45:497s–503s.Google Scholar
  14. 14.
    Lingengelter AC (1972) Varestraint testing of nickel alloys. Weld J:430s–4362sGoogle Scholar
  15. 15.
    Lin W, Lippold JC, Baeslack WA III (1993) An evaluation of heat-affected zone liquation cracking susceptibility, Part I: Development of a method for quantification. Weld J N Y 72:135s–153sGoogle Scholar

Copyright information

© International Institute of Welding 2019

Authors and Affiliations

  1. 1.Welding Engineering ProgramThe Ohio State UniversityColumbusUSA

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