Damage tolerance of wrought alloy 718 Ni- Fe-base superalloy |
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| Authors: | M Chang A K Koul P Au T Terada |
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| Affiliation: | (1) Department of Mechanical and Aerospace Engineering, Carleton University, Ottawa, Canada;(2) Structures and Materials Laboratory, Institute for Aerospace Research, National Research Council of Canada, Ottawa, Canada |
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| Abstract: | The influence of a modified heat treatment (MHT) and the standard heat treatment (SHT) on the damage tolerance of alloy 718
turbine disk material has been studied over a range of temperatures— from room temperature to 650 °. The influence of these
heat treatments on creep, low-cycle fatigue (LCF), notch sensitivity, cyclic stability, and fatigue crack growth rate (FCGR)
properties has been studied. The microstructure developed through the MHT sequence is shown to be damage tolerant over the
temperature range studied. Shot peening leads to a marked improvement in the LCF crack initiation life of the MHT material
relative to the SHT material at 650 °. Serrated grain boundaries formed through controlled precipitation of grain-boundary
5 phase are beneficial to elevated- temperature FCGRs. The S-phase precipitates formed at an angle to the grain boundaries
do not make the material notch sensitive. |
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| Keywords: | Alloy 718 damage tolerance low-cycle fatigue fatigue crack growth rate creep microstructural design serrated grain boundaries crack initiation notch sensitivity 5 phase precipitation |
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