Prediction of Ni-based alloy microstructure in wire arc additive manufacturing from cellular automata model

Abstract

Wire Arc Additive manufacturing (WAAM) process is a class of directed energy deposition processes with wire feedstock. The process enables a higher build rate than the powder-based additive process and integrates multiple custom wire feedstock to induce spatial variation of microstructure and composition. The lower speed employed in WAAM reduces the cooling rate and resultant residual stress compared to the powder bed fusion process. The systematic epitaxy across the layer creates a directional/columnar microstructure for Ni-superalloy. Here, we report cellular automata model development to predict the microstructure evolution with surface and bulk nuclei for single track and multiple layers. The cellular automata model was developed to account for secondary element addition, predict segregation, local melting, and latent heat release, as well as predict crystallographic texture/Euler angles from orientation information. We experimentally validated the layer-level microstructure and texture from SEM and EBSD, respectively, and found agreement with the CA model developed.