Effect of Temperature and Strain Amplitude on Dislocation Structure of M963 Superalloy during High-Temperature Low Cycle Fatigue

Abstract

An investigation was made on the strain-controlled low cycle fatigue (LCF) of a cast Ni-base superalloy M963 over a wide total strain range of 0.15-0.6% at a temperature range from 700 to 950 C in air. Correlations between dislocation structure and the testing temperature and applied strain amplitude were enabled through transmission electron microscopy (TEM) observation. At a low temperature region (700 and 800 C), dislocation shearing 0 precipitates by dislocation pairs and stacking faults at medium and high strain amplitudes, and a well-defined dislocation network at low total strain amplitudes were evident. At a high temperature region (900 and 950 C), dislocations by-passing 0 precipitates was the main deformation mode.

Temperature Effect on Low-Cycle Fatigue Behavior of Nickel-Based Single Crystalline Superalloy

“…The two undergo shearing together by dislocations due to a better coherent relationship, resulting in crystallographic fracture modes consequently. This is in accordance with the substructure deformation in other nickelbase superalloys [11,13,18] , i.e. shearing γ precipitates by dislocation pairs at lower temperature region and by-passing of γ precipitates at higher temperatures.…”

Corporate Effects of Temperature and Strain Range on the Low Cycle Fatigue Life of a Single-Crystal Superalloy DD10

“…It is noted that DD10 shows a decrease in N f with increasing strain amplitude at both temperatures, the same as most nickel-based superalloy [11,[14][15][16][17][18][19][20][21]27]. At all testing strain levels, the values of De p /2 in alloy DD10 are much smaller than De e /2 at both temperatures, indicating that there is no transition fatigue life (N tf ) that De p /2 = De e / 2.…”

“…It is traditionally believed that the fatigue life (N f ) decreases with the increasing total strain amplitude (e total ) under the constant temperature [11,[14][15][16][17][18][19]. However, the temperature dependence of N f also exhibits a strong dependence on e total , and N f of many superalloys does not monotonously decrease with the increasing temperature.…”

The effects of inhomogeneous microstructure and loading waveform on creep-fatigue behaviour in a forged and precipitation hardened nickel-based superalloy

“…Inconel 718 [16,17], M963 nickel-based superalloys [18], modified 9Cr-1Mo steel [17], 304 and 316 stainless steels [17], depended on those three loading waveform…”