Process chain simulation of laser powder bed fusion including heat treatment and surface hardening

Abstract

Additive manufacturing (AM) has enabled the creation of geometrically complex parts for a range of industries. However, the nature of AM often requires multiple post processing techniques to be carried out to reach the desired material properties or required surface finish. This often involves heat treatment (HT), shot peening (SP) or laser shock peening (LSP). To date, hardly any process chain modelling has been carried out on manufacturing applications with AM. This investigation focuses on the finite element (FE) modelling of the complete manufacturing process chain of an AM impeller made of IN718, including the AM, HT, LSP and SP processes. The particular AM process applied to build the impeller is laser powder bed fusion (L-PBF). Each FE process is validated individually against experimental data before being applied to the impeller process chain. The validated data from each process is mapped to the next process in the chain to investigate the combined effects of manufacturing and post processing techniques. Results have shown that high tensile residual stresses induced by AM can be reduced by approximately 75% by applying HT. SP and LSP processes can further modify remaining tensile residual stresses after HT by inducing a layer of compressive stresses at the surface. In summary, this research work has demonstrated that the simulation of AM process chains using finite element techniques is sufficiently mature to support the product and process development of industrial AM components.