What is it about?

Ni-based superalloy (IN-718) was tested at 500 °C under operational loading condition. The experiments were also performed in samples subjected to overload and overtemperature. The experiments have shown that a pre-condition of 1% strain at 700 °C would increase the fatigue life of the IN-718 at 500 °C by four times, when compared to pristine tested samples. The present results bring up the potential of improving this material fatigue performance, opening the need to further investigate the microstructure as the precondition is applied.

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Why is it important?

The results have shown that the pre-condition applied in the specimen increased the fatigue life by approximately four times, supporting the assumption that high strain associated with high temperature may reduce the effect of strain localizations, which would increase the fatigue life under lower stress levels.

Perspectives

In a next step, digital image correlation (DIC) or equivalent process could be used to measure localized strain in the area of interest to follow the slip lines at microscopic scale. Moreover, mapping of this area must be done by Electron Backscattering Diffraction (EBSD) to confirm the lattice orientations. Another important investigation would include TEM to identify if the mesoscale cubic slip plane activity, if present in IN-718, followed the zig-zag mechanism as presented by Bettge and Österle (1999), or if any signs of dislocation climb is present at elevated temperatures. In addition, different levels of pre-load condition and temperature may be tested to optimize the gain in fatigue life.

Alberto Mello
Embry-Riddle Aeronautical University

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This page is a summary of: The Effect of Pre-Thermal and -Load Conditions on IN-718 High Temperature Fatigue Life, Open Journal of Applied Sciences, January 2022, Scientific Research Publishing, Inc,,
DOI: 10.4236/ojapps.2022.123028.
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