Microstructural Impact on Fatigue Crack Growth Behavior of Alloy 718

Christian Gruber, Peter Raninger, Jürgen Maierhofer, Hans Peter Gänser, Aleksandar Stanojevic, Anton Hohenwarter, Reinhard Pippan

Research output: Contribution to journalArticleResearchpeer-review


Alloy 718 for forged parts can form a wide range of microstructures through a variety of thermo-mechanical processes, depending on the number of remelting processes, temperature and holding time of homogenization annealing, cogging and the number of forging steps depending on the forming characteristics. In industrial practice, these processing steps are tailored to achieve specific mechanical and microstructural properties in the final product. In the present work, we investigate the dependence of the threshold of stress intensity factor range ∆Kth on associated microstructural elements, namely grain size and distribution. For this purpose, a series of tests with different starting microstructures were performed at the falling stress intensity factor range, ∆K, and a load ratio of R = 0.1 to evaluate the different threshold values. Fracture initiation and crack propagation were analyzed afterward using scanning electron microscopy of the resulting fracture surfaces. In order to obtain comparable initial conditions, all specimens were brought to the same strength level by means of a two-stage aging heat treatment. In the future, this knowledge shall be used in the context of simulation-aided product development for estimating local fatigue crack propagation properties of simulated microstructures obtained from forging and heat treatment modeling.
Original languageEnglish
Article number710
Number of pages14
Issue number5
Publication statusPublished - 21 Apr 2022

Bibliographical note

Publisher Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland.


  • alloy 718
  • fracture surface
  • microstructure
  • threshold of stress intensity factor range
  • threshold value

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