Density improvement of metal parts directly fabricated via selective laser melting

In order to improve the density of metal parts fabricated via selective laser melting (SLM), the characteristics of the single-track molten pool were investigated, and the influences of scan speed and laser power on the pool width were discussed, with a direct relation between the width of powder-free region around the molten pool and the molten pool width being summarized. Then, the joint defaults of scan lines during continuous scanning were analyzed. Moreover, according to the forming characteristics of the single-track molten pool, a layer stagger strategy of laser scanning was proposed. Experimental results indicate that, by taking the proposed strategy, the density of metal parts increases to about 100%, the molten pools between inner layers and inter-layers are jointed compactly, and the tensile strength, elongation and micro-Vickers hardness of the parts reach 636 MPa, 15%~20% and 250~285, respectively. It is thus concluded that the proposed layer stagger strategy greatly improves the density and mechanical performance of metal parts fabricated via SLM.