Investigating the Effect of Heat Transfer on the Homogenity in Microstructure and Properties of Inconel 718 Alloy Fabricated by Laser Powder Bed Fusion Technique

Laser Powder Bed Fusion (LPBF) of metallic components is associated with microstructure and inhomogeneity of properties in the fabricated components. In a recent work by the authors, a novel technique of considering a border surrounding the main part during the LPBF fabrication is proposed to address the issue of inconsistency in microstructure across the cross section of LPBF-fabricated parts. This study, on the other hand, aims to investigate the effect of such border on the microstructure homogeneity along the build direction of LPBF-fabricated parts. For this purpose, a cubic sample surrounded by a cubic border was fabricated to control the rate of heat transfer and then improve the microstructure across the cross section. Also, a sample with identical dimensions and the same process parameters was printed without border as a reference to be compared. To investigate the variation of the properties along the build direction, microstructure and hardness results were compared between areas near and away the substrate for both samples. For the area away from the substrate, in both samples, a deeper pool, less surface porosity, and higher Vickers hardness was observed compared to the area near the substrate. It was found out that, regardless of the focused area, the sample fabricated with border possesses deeper pools, higher level of density as well as higher hardness value. However, in term of homogeneity along the build direction, no significant improvement was observed for the sample fabricated with the cubic border.