Thermomechanical process modelling and simulation for additive manufacturing of nanoparticle dispersed Inconel 718 alloys: Thermomechanical process modelling and simulation

In this study, a coupled transient thermomechanical finite element model is developed to examine the laser powder bed fusion (L-PBF) process of the Inconel 718 (IN718) and Oxide Dispersion Strengthened (ODS) superalloys (ODS-IN718). The linear isotropic elastic perfectly plastic constitutive model is implemented for the mechanical part whereas all the thermophysical properties are defined as fully temperature dependent. This new model enables three states of the metal including powder, liquid, and solid phases in the continuum-based finite element simulations. Besides, it can meticulously simulate multi-layered samples to assess thermomechanical performance and residual stress between layers. First, benchmark problems are revisited to verify the high accuracy of the present model for predicting transient temperature profile and residual stress accumulation. Then, thermomechanical analysis of a single-track three-layer test case is performed to investigate the L-PBF process of IN718 and ODS-IN718 samples for various laser powers and scan speeds. Also, the thermal characterization of ODS-IN718 samples is experimentally conducted. It is demonstrated that the numerical melt pool dimensions provide good agreement with experiments with an average error of 17% for melt pool dimensions. Moreover, mechanical results reveal that high tensile residual stresses accumulate in the middle part of the track. The manufacturing quality of the IN718 and ODS-IN718 samples are comprehensively compared based on the variations of stress distribution at different layers for different laser scan speeds. Also, the optimal laser scan speed is achieved to minimize the residual stresses for the ODS-IN718 alloy. Overall, ODS-IN718 has a lower residual stress than IN718 especially at lower laser scan speeds due to the enhanced thermomechanical behavior attributed to the change in material properties due to the presence of dispersed particles.