High-throughput investigation of laser powder bed fabricated Inconel 718 alloy: Fabrication, microstructure and performance

Additive manufacturing provides a possibility to realize high throughput investigation of material preparation and processing. In order to thoroughly investigate the effect of the key parameters on the soundness, microstructure and mechanical properties of the fabricated parts, sixty three combinations of laser power (twelve levels) and scanning speed (sixteen levels) with fifty eight levels of laser energy densities were realized in a single Inconel 718 alloy bar shaped specimen using the laser powder-bed fusion (L-PBF) technique. The combination of parameters varied from bottom to top of the bar, with each combination repeating every eight layers. Its spatial porosity distribution was measured by the Computed tomography (CT) test; its micro-structure was observed by optical microscope, scanning electronic microscope and EBSD; the microhardness was measured as well. A comprehensive view of the relationship of these parameters and the porosity fraction, melt pool stacking, primary grain arm spacing and microhardness was obtained. Although high laser power and slow scanning speed are helpful to achieve low porosity, but the laser power has more significant effect on the quality of the specimen than the scanning speed. Only if at high levels the volumetric laser energy density could be used as an index to correlate to the quality of the specimen. The processing chart for the guidance of L-PBF was obtained. As the laser power is higher than 140 W and the scanning speed lower than 1000 mm/s, sound specimens would be realized. This method demonstrated the great potential for high throughput investigations of the L-PBF process.