Hold time effects on the low cycle fatigue behaviour of a Nimonic PE-16 superalloy

Creep-fatigue interaction behaviour of a Nimonic PE-16 superalloy has been studied in solution-annealed condition and two double-aged conditions (micr ostructures with gamma' of 18nm and 35nm diameters) at 923 K. Tests were ca rried out over various strain amplitudes with hold times of 1 and 10 min. d uration introduced in peak tension and compression strain. The cyclic stres s response of the alloy was characterized by an initial hardening, a soften ing and a saturation regime. Further, at 923 K, the cyclic stress response was found to increase with increase in the duration of the hold. Tension ho ld was observed to be more damaging than compression hold, and the fatigue life decreased with increase in the duration of the hold in tension. Accele rated intergranular crack initiation and propagation reduced fatigue life u nder hold times in tension. Moreover, oxidation was found to reduce fatigue life under long hold periods.