The effect of loading mode on fatigue crack initiation of IN718 superalloy

The article deals with the effect of applied fatigue load with different cycle asymmetry parameters R, test temperature and loading frequency on fatigue crack initiation in IN718 superalloy. For this purpose, four sets of experimental samples were produced. The first and second sets of samples with cycle asymmetry parameter R = -1 were subjected to fatigue tests at loading frequency f ≈ 20,000 kHz and ambient temperature, respectively f ≈ 64 Hz and a temperature of 700°C. The third and fourth sets of samples with cycle asymmetry parameter R < 1 with loading frequency f ≈ 150 Hz and ambient temperature, respectively after applying annealing 800°C/72 hours. SEM fractography analysis was performed on all samples to define the fatigue crack initiation mechanism.