Exploring mechanical response and fatigue properties of laser powdered-bed fusion IN718 superalloy: Crystal plasticity modeling and defect-based life prediction

The mechanical response and fatigue properties of laser powdered-bed fusion IN718 superalloy were explored experimentally and numerically. Firstly, uniaxial fatigue testing was conducted to investigate failure mechanisms under two stress ratios in the high-cycle and very high-cycle regimes, for the as-built and solution aging conditions. The fracture surfaces reveal the competing crack nucleation behaviors driven by manufacturing or crystallographic defects. Furthermore, solution aging significantly improves fatigue life compared to as-built conditions, demonstrating higher fatigue lives under similar stress levels. Secondly, crystal plasticity finite element (CPFE) modeling was employed to develop a statistically representative volume element, enabling evaluation of the local stress and strain distributions with and without pores under cyclic loading. In addition, model parameters were calibrated using experimental stress–strain data, emphasizing the precision and validity of the proposed model. The computational results show that softened grains oriented 45° to the loading direction exhibit greater deformation. Moreover, the accumulated plastic strain increases as the loading cycles progress. Finally, a fatigue life prediction model was developed, considering the sensitivity of crack nucleation to manufacturing and crystallographic defects, along with CPFE results, showing good consistency between experimental and predicted fatigue lives across different stress levels in high-cycle and very high-cycle regimes.