Authors: Kyle A Rozman Jamie J Kruzic John S Sears Jeffrey A Hawk
Publish Date: 2015/08/29
Volume: 24, Issue: 10, Pages: 3699-3707
Abstract
The fatigue crack growth rates for nickelbased superalloy Haynes 282 were measured at 550 650 and 750 °C using compact tension specimens with a load ratio of 01 and cyclic loading frequencies of 25 and 025 Hz The crack path was observed to be primarily transgranular for all temperatures and the observed effect of increasing temperature was to increase the fatigue crack growth rates The activation energy associated with the increasing crack growth rates over these three temperatures was calculated less than 60 kJ/mol which is significantly lower than typical creep or oxidation mechanisms therefore creep and oxidation cannot explain the increase in fatigue crack growth rates Transmission electron microscopy was done on selected samples removed from the cyclic plastic zone and a trend of decreasing dislocation density was observed with increasing temperature Accordingly the trend of increasing crack growth rates with increasing temperature was attributed to softening associated with thermally assisted cross slip and dislocation annihilation
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