Single crystal PWA 1483 superalloy: Dislocation rearrangement and damping phenomena

Abstract

a b s t r a c tThe structural stability of the single-crystal PWA 1483 superalloy has been investigated by internal friction (IF) and dynamic modulus measurements from room temperature to 1073 K. The examined samples were in the solubilized state.The vibrating reed technique with electrostatic excitation and frequency modulation detection of flexural vibrations has been employed. Frequency was ∼350 Hz.IF spectra recorded in successive test runs on the same samples show a Q −1 maximum (M1) above 623 K, whose intensity and position change from one run to another; in correspondence with M1 the modulus undergoes a slow decrease followed by a sudden increase. Sometimes another maximum (M2) has been observed at lower temperature (∼523 K).After each run the values of the modulus and of Q −1 change indicating that a progressive irreversible transformation occurs. Damping phenomena have been attributed to the rearrangement of dislocation structures in the disordered matrix. This rearrangement modifies the density and the average distance of pinning points. This explanation is supported by transmission electron microscopy (TEM) observations.

Evaluation of Structural Stability of Materials through Mechanical Spectroscopy: Four Case Studies

“…These results, illustrated in Figure 4a, are compatible with an irreversible microstructural transformation taking place in successive steps giving rise to Q −1 maxima [11]. When the transformation has been completed, the structure is stable and the maxima are no more observed.…”

Welding of IN792 DS superalloy by electron beam

“…Ni‐based superalloys are widely used in the components (disks and blades) of aeronautic engines and gas turbines operating at the highest temperatures . Their microstructure mainly consists of cuboidal shaped particles of the ordered γ'‐phase embedded in the disordered γ‐phase matrix . During the service life, the mechanical parts made of superalloys operate under high stress and temperature in a quite aggressive environment, therefore, sometimes surface cracks form leading to sudden rupture.…”

“…[1,2] Their microstructure mainly consists of cuboidal shaped particles of the ordered γ'-phase embedded in the disordered γ-phase matrix. [3] During the service life, the mechanical parts made of superalloys operate under high stress and temperature in a quite aggressive environment, therefore, sometimes surface cracks form leading to sudden rupture. Because these mechanical components are extremely expensive, their repairing by welding is more advantageous than replacement; however, it is not an easy task.…”

Relation between the microstructure and microchemistry in Ni‐based superalloy

“…Ni‐based superalloys are employed in hot parts, such as disk and blades, of gas turbines and aeronautical engines. For their applications at high temperature, the mechanical and microstructural stability is of the utmost importance …”

“…For their applications at high temperature, the mechanical and microstructural stability is of the utmost importance. [1][2][3][4] The microstructure of single crystal Ni-based super-alloys consists in ordered g′ precipitates Ni 3 (Ti,Al) L1 2 coherently embedded in the solid solution g matrix. [5] The g′ particles, with a roughly cubic shape, are arranged along the <001> directions and are separated by narrow g channels.…”