Precontouring as a Tool to Improve the Laser Powder Bed Fusion Printability of Inconel939 Thin Walls

This work investigates the influence of adding a contour scan prior to hatching (precontouring) on the printability of Inconel 939 thin-wall sections produced by laser powder bed fusion. Walls with thicknesses ranging from 500 to 1500 mu m, manufactured with two hatch scanning parameter sets that give rise to different microstructures and very high density in bulk samples of the same alloy, are investigated. It is shown that, while the texture as well as the grain size and shape is only influenced moderately by the contour scanning strategy, precontouring does lead to a significant reduction of the melt pool depth, an effect that is increasingly pronounced with decreasing wall thickness. This work highlights the role of the precontour scan as a heat sink, shifting the normalized enthalpy input toward lower values and thus limiting the accumulation of excess heat. Precontouring is put forward as a scanning strategy to improve the manufacturability of thin sections.