Unexpected δ-Phase Formation in Additive-Manufactured Ni-Based Superalloy

Y. Idell*, L. E. Levine, A. J. Allen, F. Zhang, C. E. Campbell, G. B. Olson, J. Gong, D. R. Snyder, H. Z. Deutchman

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

51 Scopus citations


An as-built and solutionized Ni-based superalloy built by additive manufacturing through a direct metal laser sintering technique is characterized to understand the microstructural differences as compared to the as-wrought alloy. Initially, each layer undergoes rapid solidification as it is melted by the laser; however, as the part is built, the underlying layers experience a variety of heating and cooling cycles that produce significant microsegregation of niobium which allows for the formation of the deleterious δ-phase. The as-built microstructure was characterized through Vickers hardness, optical microscopy, scanning and transmission electron microscopy, electron back-scattering diffraction, x-ray diffraction, and synchrotron x-ray microLaue diffraction. The isothermal formation and growth of the δ-phase were characterized using synchrotron-based in situ small angle and wide angle x-ray scattering experiments. These experimental results are compared with multicomponent diffusion simulations that predict the phase fraction and composition. The high residual stresses and unexpected formation of the δ-phase will require further annealing treatments to be designed so as to remove these deficiencies and obtain an optimized microstructure.

Original languageEnglish (US)
Pages (from-to)950-959
Number of pages10
Issue number3
StatePublished - Mar 1 2016

ASJC Scopus subject areas

  • Materials Science(all)
  • Engineering(all)


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