Metallurgical and Materials Transactions A

, Volume 33, Issue 6, pp 1681–1687 | Cite as

Environmentally assisted, sustained-load crack growth in powder metallurgy nickel-based superalloys

  • Zhifan Huang
  • Carl Iwashita
  • Irene Chou
  • Robert P. Wei


To examine the influence of niobium (Nb) on sustained-load crack growth (SLCG) in oxygen, three powder metallurgy (P/M) nickel-based superalloys, with nominal compositions similar to IN100, but with 0, 2.5, and 5 wt pct of Nb, are used. These alloys are gamma-prime (γ’) strengthened and have comparable volume fractions (53 vol pct) of γ’ precipitates. The SLCG experiments are conducted in high-purity oxygen and argon at 873, 923, and 973 K. The environmental cracking sensitivity (ECS) for the alloys with 2.5 and 5 wt pct of Nb is consistent with that of INCONEL 718 and supports the previously identified role of Nb-rich carbides in enhancing crack growth. The susceptibility of the Nb-free alloy to oxygen, however, is much greater than expected. The apparent activation energy for crack growth in oxygen was found to depend on stress-intensity-factor (K) levels for the Nb-containing alloys and ranged from about 320 to 260 kJ/mol for K levels of 35 to 60 MPa√m. It was nearly independent of K at about 250 kJ/mol for the Nb-free alloy. The results are discussed in terms of the rate-controlling process and of the mechanism for crack-growth enhancement.


Material Transaction Crack Growth Rate Apparent Activation Energy Representative Transmission Electron Microscopy Micrographs Enhance Crack Growth 
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Copyright information

© ASM International & TMS-The Minerals, Metals and Materials Society 2002

Authors and Affiliations

  • Zhifan Huang
    • 1
  • Carl Iwashita
    • 2
  • Irene Chou
    • 3
  • Robert P. Wei
    • 4
  1. 1.Eastman KodakRochester
  2. 2.LSI LogicMilpitas
  3. 3.Applied MaterialsSanta Clara
  4. 4.the Department of Mechanical Engineering and MechanicsLehigh UniversityBethlehem

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