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

10 Citations (Scopus)

Abstract

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.

LanguageEnglish
Title of host publicationSuperalloys 2012
Pages705-714
Number of pages10
DOIs
Publication statusPublished - 2 Oct 2012

Fingerprint

Superalloys
Alloying
Thermal expansion
High temperature applications
Neutron scattering
X ray scattering
Temperature
Precipitates
Substitution reactions
Aging of materials
Diffraction
Heat treatment
Cooling
Oxidation
Air
Experiments

Keywords

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

Cite this

Yan, H. Y., Vorontsov, V. A., Coakley, J., Jones, N. G., Stone, H. J., & Dye, D. (2012). Quaternary Alloying Effects and the Prospects for a New Generation of Co-Base Superalloys. In Superalloys 2012 (pp. 705-714) https://doi.org/10.1002/9781118516430.ch78
Yan, Hui Yu ; Vorontsov, Vassili A. ; Coakley, James ; Jones, Nicholas G. ; Stone, Howard J. ; Dye, David. / Quaternary Alloying Effects and the Prospects for a New Generation of Co-Base Superalloys. Superalloys 2012. 2012. pp. 705-714
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Quaternary Alloying Effects and the Prospects for a New Generation of Co-Base Superalloys. / Yan, Hui Yu; Vorontsov, Vassili A.; Coakley, James; Jones, Nicholas G.; Stone, Howard J.; Dye, David.

Superalloys 2012. 2012. p. 705-714.

Research output: Chapter in Book/Report/Conference proceedingChapter

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AB - 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.

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