Build Height Process Control in Directed Energy Deposition

A dimensionless number to predict build height has been developed for the additive manufacturing technique of directed energy deposition (DED). By using the dimensionless number, process parameters including laser power, laser traverse speed, powder flow rate, layer thickness, and hatch spacing can be predicted and optimized. The dimensionless number is a balance of heat input and heat dissipation and provides a window for increased efficiency for build height in the DED process. To validate the prediction, a range of materials were explored. Samples of 316L stainless steel were used to calibrate the process, and in situ alloying of Fe-Ni-Mo-Cr alloys and Mo-Si-B alloys were also fabricated to test the relationships with varied thermophysical property alloy systems. The build height is coupled to the cooling rate, so the technique can be used to tailor dendrite arm spacings and microsegregation. Implications on autonomous control as well as microstructural tailoring will be presented.