Critical assessment of the impact of process parameters on vertical roughness and hardness of thin walls of AlSi10Mg processed by laser powder bed fusion

This work deals with the impact of prominent process parameters in laser powder bed fusion (L-PBF) technique, also called selective laser melting (SLM), on relevant properties of AlSi10Mg such as surface roughness and hardness. More particularly, the influence of scanning strategies, track energy density (TED), and of the offset between the contours and the bulk hatching were scrutinized. Basic thin structures such as single wall tracks (SWT) and ultra thin walls (UTW) were used to isolate the effect of the TED and of the offset between parallel melt pool tracks on the vertical roughness, respectively. It is shown that the TED reduces the level of roughness mostly due to a geometrical effect. The optimum range of TED is shown to be at the beginning of the keyhole conditions, at the expense of the amount of sub-surface porosities and of hardness. Increasing the offset also allows reducing the roughness. Thicker structures with contours and bulk hatching were also used and brought the same conclusions. In this work, low levels of roughness (about 4 mu m) have been obtained on vertical walls without any post-treatment but at the expense of the mechanical properties.