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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
Article

Abstract

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.

Keywords

Material Transaction Crack Growth Rate Apparent Activation Energy Representative Transmission Electron Microscopy Micrographs Enhance Crack Growth 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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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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