Abstract
Fatigue strength of Ni base superalloy IN 713LC was experimentally determined at 800°C in air using load controlled cycling with tensile mean stress. The constant fatigue life diagram has been constructed with particular attention to the influence of small stress amplitudes at high mean stresses. The mechanism of Stage I initiation of fatigue cracks, the role of casting defects and cavities and their effect on the fatigue strength have been discussed.

Key words
IN 713LC, high-cycle fatigue, constant fatigue life diagram, fatigue crack initiation

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