Peculiarities of formation of defects initiating fatigue faults in granular alloy EP741NP

Abstract

The samples of EP741NP alloy destroyed during fatigue testing were investigated by means of transmission electron microscopy, energy-dispersive X-ray microanalysis and electron diffraction. The composition and crystal structure of defects detected at the boundaries of fatigue cracks were studied in details. It was shown that such defects mainly have the morphology of elongated flat "carpets" containing NiO, CTixNb1–x, amorphous AlOx, HfO2, Al2O3, β-Al2O3, Al2MgO4, Co7Mo6, Co3O4, S4Ti3, NbO2, TiO2, as well as amorphous regions containing C, O, Ca, S, Na and Cl. Assumptions were made about the source and of time formation of the studied defects.