Defects Initiating Fatigue Faults in Granular Alloy EP741NP (Part II)

A three-dimensional reconstruction of the microstructure of the defects associated with the formation of fatigue cracks in samples destroyed during low-cycle fatigued tests has been performed by serial-section focused ion beam tomography. The geometric parameters of defects containing Hf, Nb, Ti, Al, and Ni, identified during 3D reconstruction, were determined. The morphology of individual particles is presented by a set of shapes that form flat (carpet-like) conglomerates up to several tens of microns in size, which cannot be detected by nondestructive testing methods. The revealed morphological features make it possible to propose a complex of measures aimed at increasing the service life of parts made of granulated heat-resistant nickel alloy EP741NP; this is an important practical result.