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: Contribution to conferenceProceedingpeer-review

21 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
Number of pages10
Publication statusPublished - 1 Dec 2012
Event12th International Symposium on Superalloys, Superalloys 2012 - Seven Springs, PA, United States
Duration: 9 Sep 201213 Sep 2012


Conference12th International Symposium on Superalloys, Superalloys 2012
Country/TerritoryUnited States
CitySeven Springs, PA


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

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