Fatigue Behavior and Life Prediction Model of a Nickel-Base Superalloy under Different Strain Conditions

Abstract

The fatigue behavior of a nickel-base superalloy was investigated under total strain-controlled mode at high temperature. The fatigue life, cyclic stress response behavior and hysteresis loop of the superalloy were investigated under isothermal low cycle fatigue (LCF) conditions. The superalloy exhibited cyclic hardening and softening behaviors during the process of fatigue loading. The hysteresis loop shifted downwards slightly with the increase of the number of cycles. The fatigue life under different strain amplitudes reflects the interactions of dislocations and £ A precipitates at elevated temperature. Three life prediction models to evaluate the fatigue life of the superalloy were evaluated for the LCF tests. The prediction values obtained by Manson-Coffin relationship agree well with the experimental results. The mechanisms of LCF were revealed through the observation of the microstructures by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The main deformation mechanism of the superalloy is the different interactions between dislocations and £ A precipitates.

Low-Cycle Fatigue and Creep-Fatigue Behaviors of a Second-Generation Nickel-Based Single-Crystal Superalloy at 760 °C

“…It was confirmed that with the strain amplitude increasing, the density of dislocation increases, the plastic deformation state and microstructure switch from fully anisotropic to isotropic [15]. The cyclic stress response, including the cyclic hardening and cyclic softening, is related to dislocation or SF which depends on strain amplitude and fatigue testing temperature [25]. Li found that the slip bands can be observed and the movement of dislocation was not homogeneous at 750 °C.…”

Fatigue Behavior of Additively Manufactured IN718 with Columnar Grains

“…A cyclic load was applied to virtual RM samples along the y-axis direction, as shown in Figure 1c. Experimental fatigue test data (i.e., stress-strain data at the first cycle, at half life, and the number of cycles to failure) obtained under strain-controlled conditions for IN718 are available in the literature, [32] which provided information on the fatigue scatter under various loading conditions. Similar to the experimental setup, fully reversed tests (strain ratio R ¼ À1) with different applied strain amplitudes were conducted using the CP model.…”