Dislocation Densities and Velocities within the γ Channels of an SX Superalloy during In Situ High-Temperature Creep Tests

Abstract

The high-temperature creep behavior of a rafted [001] oriented AM1 Ni-based single crystal superalloy was investigated during in situ creep tests on synchrotrons. Experiments were performed at constant temperatures under variable applied stress in order to study the response (plastic strain, load transfer) to stress jumps. Using two different diffraction techniques in transmission (Laue) geometry, it was possible to measure the average lattice parameters of both the γ matrix and the γ′ rafts in the [100] direction at intervals shorter than 300 s. The absolute precision with both diffraction techniques of the constrained transverse mismatch (in the rafts’ plane) is about 10−5. After stress jumps, special attention is given to the evolution of plastic strain within the γ channels. The relaxation of the Von Mises stress at leveled applied stress shows evidence of dislocation multiplication within the γ channels. From the analysis, we showed an interaction between plastic stress and dislocation density of the γ phase.

Defect Creation in the Root of Single-Crystalline Turbine Blades Made of Ni-Based Superalloy

“…Therefore, it is necessary to test for defects in the root layers located in the vicinity of the plane of the S–R connection and to analyze how they were created. The density of dislocations and vacancy-type defects are important for creep processes in Ni-based single-crystalline superalloys [19].…”

Variation of Crystal Orientation and Dendrite Array Generated in the Root of SX Turbine Blades

“…The best method for such studies is the X-ray diffraction topography with the use of a divergent beam emitted from a microfocus X-ray tube and covering the whole sample surface that oscillates during exposure. By this method, a large area (from a dozen to several dozen cm 2 ) of the blade with very low disorientation (arc minutes), as well as with the high disorientation (arc degrees), can be visualized in single topogram, which cannot be realized by other diffraction methods (e.g., EBSD or Berg-Barrett topography) [22,23]. In addition, the X-ray diffraction topography method allows analyzing the creation of the dendrite array during the dendrites' lateral growth in blades [19].…”