Advanced Electron Microscopy and Microcomputed Tomography Analysis of Single‐Crystal Ni‐Base Superalloys After Short‐Term Multiaxial Creep

This study extends the findings of Cao et al. (2020) on the creep rupture behavior of circular double‐notch tensile (CDNT) specimens of the Ni‐base superalloy single‐crystal ERBO‐1, where a triaxial stress state governs. Additional creep tests are conducted at 950 °C and 400 MPa on specimens loaded in [001], [110], and [111] directions and interrupted after 80 h. Complementary characterization methods, including electron backscattered diffraction, focused ion beam‐scanning electron microscopy tomography, scanning transmission electron microscopy, and microcomputed tomography, were used to study the formation of topologically close‐packed phase (TCP)‐phase particles and micropores. Early creep failure of the [110] specimen is caused by a critical alignment of micropores, a higher resolved shear stresses acting on a higher number of dislocations in the γ and γ′ phases, and higher volume fraction of TCP‐phase particles. After 80 h, the [111] specimen shows significantly more localized deformation and a 1.4 times higher displacement than the [001] and [110] specimens. The [110] specimen shows distinct local misorientations from the mean orientation of the order of up to 2°. The findings provide a deeper understanding of the microstructural factors that influence creep behavior and rupture life in CDNT specimens of single‐crystal Ni‐base superalloys.