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Metallurgical and Materials Transactions A

, Volume 49, Issue 9, pp 3838–3853 | Cite as

An Abrupt Transition to an Intergranular Failure Mode in the Near-Threshold Fatigue Crack Growth Regime in Ni-Based Superalloys

  • J. Telesman
  • T. M. Smith
  • T. P. Gabb
  • A. J. Ring
Topical Collection: Superalloys and Their Applications
  • 280 Downloads
Part of the following topical collections:
  1. Third European Symposium on Superalloys and their Applications

Abstract

Cyclic near-threshold fatigue crack growth (FCG) behavior of two disk superalloys was evaluated and was shown to exhibit an unexpected sudden failure mode transition from a mostly transgranular failure mode at higher stress intensity factor ranges to an almost completely intergranular failure mode in the threshold regime. The change in failure modes was associated with a crossover of FCG resistance curves in which the conditions that produced higher FCG rates in the Paris regime resulted in lower FCG rates and increased ∆Kth values in the threshold region. High-resolution scanning and transmission electron microscopy were used to carefully characterize the crack tips at these near-threshold conditions. Formation of stable Al-oxide followed by Cr-oxide and Ti-oxides was found to occur at the crack tip prior to formation of unstable oxides. To contrast with the threshold failure mode regime, a quantitative assessment of the role that the intergranular failure mode has on cyclic FCG behavior in the Paris regime was also performed. It was demonstrated that even a very limited intergranular failure content dominates the FCG response under mixed mode failure conditions.

Notes

Acknowledgment

This work supports the objectives and goals of NASA’s Advanced Air Transportation Technology Project funded by the Aeronautics Research Mission Directorate.

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Copyright information

© This is a U.S. government work and its text is not subject to copyright protection in the United States; however, its text may be subject to foreign copyright protection 2018

Authors and Affiliations

  • J. Telesman
    • 1
  • T. M. Smith
    • 1
  • T. P. Gabb
    • 1
  • A. J. Ring
    • 1
  1. 1.NASA Glenn Research CenterClevelandUSA

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