Effect of temperature on fatigue behavior and deformation mechanisms of nickel-based superalloy SU-263

The LCF behavior of SU-263 was investigated at various temperatures (1073, 1123, and 1173 K) and strain amplitudes of ± 0.4 to 0.8% at a constant strain rate of 3 × 10^-3 s⁻¹. The alloy displayed initial hardening followed by extensive cyclic softening until failure. It is observed that the presence of dislocation networks absorbs mobile dislocation, and the shearing of γ′ precipitates were responsible for cyclic softening at 1073 and 1123 K, whereas dissolution of γ′ precipitate and dislocation annihilation were responsible for cyclic softening at 1173 K. At elevated temperatures, the LCF behavior is significantly influenced by time-dependent processes such as dynamic strain aging (DSA), and oxidation. The occurrence of DSA manifests in the form of serrated plastic flow in stress–strain hysteresis loops, reduced half-life plastic strain amplitude, and increased cyclic work hardening. The alloy exhibits linear behavior in the Coffin-Manson (C-M) plot at 1073 and 1173 K. However, the C-M plot shows bi-linear behavior at 1123 K with the corresponding shift in the deformation mechanism at ± 0.5% strain amplitude. This study focuses on understanding the effects of temperature on fatigue behavior and the associated deformation mechanisms by using characterization techniques, such as scanning and transmission electron microscopy.