The role of tool path on microstructure uniformity in large-format additive manufacturing: integrated thermo-metallurgical-mechanical approach

Directed energy deposition (DED) of large metal components has clear potential to revolutionise supply chains in several sectors, including marine & offshore and oil & gas. To insert this technology in production, ensuring part quality and consistency is of primary importance. However, such insertion is hindered by bottleneck issues arising from the manufacturing process, including part distortion and non-uniform mechanical properties. To address this important industrial need, an integrated thermo-metallurgical-mechanical numerical model capable of directly reading the robot tool-path (g-code) as well as the component shape, is here developed in-house and tailored to steel EH36, which is of particular relevance to the marine, offshore and oil & gas sectors. The model computes temperature at part scale, microstructure (phase fraction distribution) and residual stress and distortion, where each step of the chain is informed by the previous one. After demonstrating the framework on a single bead and thin wall geometries, the framework is applied to investigate the role of tool path in printing a more complex geometry. The presented framework allows to digitally correlate part design, process parameters, and tool path with microstructure distribution, residual stresses, and distortion, supporting digital process development in DED of large metal components.