On the Influence of Nb/Ti Ratio on Environmentally-Assisted Crack Growth in High-Strength Nickel-Based Superalloys

Research output: Contribution to journalArticlepeer-review


  • A. A.N. Németh
  • D. J. Crudden
  • V. Kuksenko
  • C. H. Liebscher
  • D. E.J. Armstrong
  • A. J. Wilkinson
  • R. C. Reed

Colleges, School and Institutes

External organisations

  • University of Oxford
  • Max-Planck-Institut für Eisenforschung


The effect of Nb/Ti ratio on environmentally-assisted crack growth of three prototype Ni-based superalloys is studied. For these alloys, the yield strength is unaltered with increasing Nb/Ti ratio due to an increase in grain size. This situation has allowed the rationalization of the factors influencing damage tolerance at 700 °C. Primary intergranular cracks have been investigated using energy-dispersive X-ray spectroscopy in a scanning transmission electron microscope and the analysis of electron back-scatter diffraction patterns. Any possible detrimental effect of Nb on the observed crack tip damage due to Nb-rich oxide formation is not observed. Instead, evidence is presented to indicate that the tertiary γ′-precipitates are dissolving ahead of the crack consistent with the formation of oxides such as alumina and rutile. Our results have implications for alloy design efforts; at any given strength level, both more and less damage-tolerant variants of these alloys can be designed.


Original languageEnglish
Pages (from-to)1-15
Number of pages15
JournalMetallurgical and Materials Transactions A: Physical Metallurgy and Materials Science
Early online date11 May 2018
Publication statusE-pub ahead of print - 11 May 2018