Impact of IN718 bimodal powder size distribution on the performance and productivity of laser powder bed fusion additive manufacturing process

Bimodal powders of IN718 were obtained by adding a fine powder (D10-D90: 6.2-16.9 mu m) to a typical laser powder bed fusion (L-PBF) powder (coarse powder, D10-D90: 26.5-50.5 mu m) in various volume fractions. The fine powder was selected to generate an Alpha (Rosin-Rammler fit parameter) of 3.17 based on literature data and powder availability. The 83.75/16.25 Vol% of coarse/fine blend was chosen for the combination of reduced interparticle spacing/improved particle coordination number while retaining free flowing behavior. A new index, termed Raking Index (R), is defined to incorporate apparent density and Confined Specific Flow Energy as one parameter for assessing rakeability. Our results show that when R > 36 mJ/cm(3) IN718 forms a dense and rakeable powder bed. After L-PBF processing, the use of the 83.75/16.25 blend resulted in 10% increase in process productivity, higher IN718 tensile strength, and reduced mechanical anisotropy. (C) 2020 Elsevier B.V. All rights reserved.