Residual stress and distortion control in wire-arc additive manufacturing process through novel modular substrate

Wire arc additive manufacturing (WAAM) is a proven technology in metal additive manufacturing (AM), which can produce large-scale components at a faster production rate. Since WAAM adopts a welding heat source for metal deposition over the substrate, severe thermal gradients develop around the deposition resulting in residual stresses in the substrate, thereby distorting the substrate. In the case of area filling in metal AM processes, heat accumulation is progressive and a large amount of heat is accumulated at the end of the deposition. This leads to thermal imbalance over the substrate and an increase in the shrinkage forces during cooling, thereby causing higher distortion. This paper mainly deals with the mitigation of distortion in the substrate for area filling caused by the thermal imbalance over the substrate. This thermal imbalance is addressed in two ways; a) by selectively insulating and b) by selectively conducting the heat from the substrate. Simulations are conducted to study the thermal evolution during area filling and counterbalance the heat by insulating and conducting the substrate selectively during experimental deposition. A comparative assessment of distortions of the full conduction, full insulation, selective conduction and selective insulation cases is detailed. The selective thermal management strategy showed lower thermal imbalance over the substrate resulting in lower distortion.