Contour design to improve topographical and microstructural characteristics of Alloy 718 manufactured using electron beam-powder bed fusion

Abstract Additive manufacturing (AM) processes are being frequently used in industry as they allow the manufacture of complex parts and have reduced lead times. Electron beam-powder bed fusion (EB-PBF) as an AM technology is known for its near-net-shape production capacity with low residual stress. However, the surface quality of the manufactured parts is a major obstacle for the wider industrial adoption of this technique, especially when enhanced mechanical performance is taken into consideration. Identifying the origins of surface features such as satellite particles and sharp valleys on the parts manufactured by EB-PBF is important for a better understanding of the process. Moreover, understanding the influence of the contour melting strategy, by altering process parameters, on the surface roughness of the parts and the number of near-surface defects is highly critical. In this study, processing parameters of the EB-PBF process such as scanning speed, beam current, focus offset, and number of contours (one or two) with the linear melting strategy were investigated. A sample manufactured using Arcam-recommended process parameters (three contours with the spot melting strategy) was used as a reference. For the samples with one contour, the scanning speed had the greatest effect on the arithmetical mean height (Sa), and for the samples with two contours, the beam current and focus offset had the greatest effect. For the samples with two contours, a lower focus offset and lower scan speed (at a higher beam current) resulted in a lower Sa; however, increasing the scan speed for the samples with one contour decreased the Sa. In general, the samples with two contours provided a lower Sa (∼22%) but with slightly higher porosity (∼8%) compared to the samples with one contour. Fewer defects were detected with a lower scanning speed and higher beam current. The number of defects and the Sa for the samples with two contours prepared using the linear melting strategy were ∼85% and 16%, respectively, lower than those of samples prepared using the spot melting strategy from the recommended process parameters.