Modeling and control of remelting in high-energy beam additive manufacturing

Abstract

Increasing demand for high-quality additive manufactured parts in the aerospace, automotive, medical, and oil and gas industries requires careful control of the part microstructure, residual stress, and density homogeneity. In order to improve part quality, partial remelting of the as-built material during subsequent beam scans is desirable. Here, we make use of computer simulations to explicitly study remelting in laser- or electron beam-melting additive manufacturing. By explicitly implementing phase transformations between the powder, the liquid, and the bulk, we track the amount of material that is subject to remelting. The influence of the beam parameters, such as the beam size, scan speed and power, are investigated and both the cases of an exponential as well as a linear beam absorption profile are considered. We find that, at constant beam cross section, there is an optimal beam shape for remelting. Further, we show how the optimal shape changes when the scan speed is changed and in this case interlayer remelting is also specifically addressed. Calculations are presented for the model case of AISI 316L stainless steel but can be extended to a wide class of metals.