The role of powder layer thickness on the quality of SLM printed parts

Achieving good mechanical properties as well as the dimensional accuracy and the smooth surface quality of selective laser melting printed parts with minimal post treatments are essential in additive manufacturing. In the present study, Inconel 718 samples with different powder layer thickness (20, 30, 40 and 50 μm) were additively fabricated using 3D Systems ProX-300 machine. The results reveal that the lower the layer thickness, the denser and good dimensional accuracy were achieved. Marginally higher mechanical properties and microhardness were also obtained at the lower thickness while the failure strain was still high. This can be explained through significant change in the microstructure due to different cooling rate and thermal cycles. In addition, the formation of ɤ′ and ɤ″ intermetallic phases, which were well distributed in the matrix and grain boundaries, during heating/cooling, gave rise in the strengths. Fractography shows the plastic deformation band due to work hardening and the crack initiation sites at sub-micro/micro pores, lack of fusion areas and the boundary of unmelted particles. The study would guide engineers balance their options between the production rate and the building parts' quality.