JOM

, Volume 66, Issue 12, pp 2495–2501

A New Polycrystalline Co-Ni Superalloy

  • M. Knop
  • P. Mulvey
  • F. Ismail
  • A. Radecka
  • K. M. Rahman
  • T. C. Lindley
  • B. A. Shollock
  • M. C. Hardy
  • M. P. Moody
  • T. L. Martin
  • P. A. J. Bagot
  • D. Dye
Article

DOI: 10.1007/s11837-014-1175-9

Cite this article as:
Knop, M., Mulvey, P., Ismail, F. et al. JOM (2014) 66: 2495. doi:10.1007/s11837-014-1175-9

Abstract

In 2006, a new-ordered L12 phase, Co3(Al,W), was discovered that can form coherently in a face-centered cubic (fcc) A1 Co matrix. Since then, a community has developed that is attempting to take these alloys forward into practical applications in gas turbines. A new candidate polycrystalline Co-Ni γ/γ′ superalloy, V208C, is presented that has the nominal composition 36Co-35Ni-15Cr-10Al-3W-1Ta (at.%). The alloy was produced by conventional powder metallurgy superalloy methods. After forging, a γ′ fraction of ~56% and a secondary γ′ size of 88 nm were obtained, with a grain size of 2.5 μm. The solvus temperature was 1000°C. The density was found to be 8.52 g cm−3, which is similar to existing Ni alloys with this level of γ′. The alloy showed the flow stress anomaly and a yield strength of 920 MPa at room temperature and 820 MPa at 800°C, similar to that of Mar-M247. These values are significantly higher than those found for either conventional solution and carbide-strengthened Co alloys or the γ/γ′ Co superalloys presented in the literature thus far. The oxidation resistance, with a mass gain of 0.08 mg cm−2 in 100 h at 800°C, is also comparable with that of existing high-temperature Ni superalloys. These results suggest that Co-based and Co-Ni superalloys may hold some promise for the future in gas turbine applications.

Copyright information

© The Minerals, Metals & Materials Society 2014

Authors and Affiliations

  • M. Knop
    • 1
  • P. Mulvey
    • 1
  • F. Ismail
    • 1
  • A. Radecka
    • 1
  • K. M. Rahman
    • 1
  • T. C. Lindley
    • 1
  • B. A. Shollock
    • 1
    • 2
  • M. C. Hardy
    • 3
  • M. P. Moody
    • 4
  • T. L. Martin
    • 4
  • P. A. J. Bagot
    • 4
  • D. Dye
    • 1
  1. 1.Department of MaterialsRoyal School of Mines, Imperial College LondonLondonUK
  2. 2.WMG, University of WarwickCoventryUK
  3. 3.Rolls-Royce plcDerbyUK
  4. 4.Department of MaterialsUniversity of OxfordOxfordUK

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