Effects of Cr on the properties of multicomponent cobalt-based superalloys with ultra high γ’ volume fraction

Ding Wen Chung, Jacques P. Toinin, Eric A. Lass, David N. Seidman, David C. Dunand*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

9 Scopus citations

Abstract

Chromium is known to confer oxidation resistance on Co-based superalloys. Herein we studied the influence of Cr concentration on the properties of a Co-based superalloy, Co–30Ni–11Al–2Ti-5.5W-2.5Ta-0.1B (at.%), with high γ’-volume fractions (up to 98%). Additions of 4, 8, or 12 at.% Cr decreased the γ’-solvus temperature and the γ’-volume fraction, while also reducing the mean radius of γ’-particles. Synchrotron X-ray diffraction and atom-probe tomography confirmed that Cr reduces the lattice parameter misfit by altering the partitioning behavior of W between the γ- and γ’-phases. Concomitantly, an increase in Cr content significantly improved the oxidation resistance of the alloy. The results indicate that 4 at.% Cr is sufficient to decrease the oxidation rate by two orders of magnitude. A creep study at 850 C revealed that Cr does not affect adversely the creep performance in high γ’-volume fraction Co-based superalloys, but the tendency toward γ’ rafting changes with Cr concentration. Compared to Ni3Al intermetallic compounds, the alloys with high γ’-volume fraction studied exhibited a significantly higher creep resistance. This may be attributed to the increase in antiphase boundary energy caused by the addition of Cr, Ti, or Ta, and significant solid-solution hardening in the Co-based intermetallic γ’-phase.

Original languageEnglish (US)
Article number154790
JournalJournal of Alloys and Compounds
Volume832
DOIs
StatePublished - Aug 15 2020

Keywords

  • Cobalt-based superalloys
  • Creep
  • Lattice parameter misfit
  • Oxidation
  • Partitioning

ASJC Scopus subject areas

  • Mechanics of Materials
  • Mechanical Engineering
  • Metals and Alloys
  • Materials Chemistry

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