Quaternary Alloying Effects and the Prospects for a New Generation of Co-Base Superalloys

Hui Yu Yan, Vassili A. Vorontsov, James Coakley, Nicholas G. Jones, Howard J. Stone, David Dye

Research output: Chapter in Book/Report/Conference proceedingChapter

14 Citations (Scopus)


Polycrystalline Co-Al-W alloys with quaternary alloying substitutions have been studied to investigate whether this alloy system might be attractive as an alternative to Ni-base superalloys in high temperature applications. A process route for the alloys was developed and an initial aging heat treatment established. The initial findings indicate that the addition of Ti, Ta and Ni increases the solvus temperature, whereas the addition of Mo lowers it slightly. The addition of Ti, Ta and Ni to the base alloy increased the γ' precipitate size, whereas the addition of Mo had a negligible effect. Diffraction measurements were performed using both X-ray and neutron scattering. Positive lattice misfit values were obtained at both room and elevated temperatures; moreover, the lattice misfit increased with temperature. The thermal expansion coefficient of the γ phase was similar to reference data for Co, whereas the γ' phase had a greater thermal expansion coefficient than the γ phase. Finally, cyclic oxidation experiments have been carried out in air at 800 C°. The CoO scales grown were not protective, and the alloys suffered from spallation during cooling.

Original languageEnglish
Title of host publicationSuperalloys 2012
PublisherJohn Wiley & Sons Inc.
Number of pages10
ISBN (Print)9780470943205
Publication statusPublished - 2 Oct 2012


  • Co3(Al,W)
  • cobalt
  • lattice misfit
  • oxidation
  • solvus
  • superalloys
  • alloys

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