Fatigue Characterization and Modeling of Additively Manufactured Hastelloy-X Superalloy

Quasi-static and fatigue behavior of laser powder-bed fusion Hastelloy X (LPBF-HX) specimens were studied. Tension–compression asymmetry was evaluated through a wide range of plastic strains. LPBF-HX specimens are not showing loading direction dependency during monotonic tension and compression tests at low plastic strains. LPBF-HX showed primary hardening under cyclic loading, followed by softening at high strain amplitudes in fully reversed strain-controlled fatigue tests. As the later softening masks the primary hardening, the half-life cyclic stress–strain curve coincides with the monotonic stress–strain curve. Various strain- and energy-based fatigue models were calibrated using the experimental strain-life data and were utilized to predict the fatigue life under different loading conditions with mean stresses. The Jahed–Varvani and Smith–Watson–Topper models showed good results. A fatigue design curve with 95% reliability and 90% confidence level was also constructed using the approximate Owen tolerance limit.[graphic not available: see fulltext]