The effect of selective laser melting process parameters and remelting scanning strategy on relative density and surface hardness of stainless steel 316L

Selective laser melting (SLM) process is the foremost metal additive manufacturing (AM) technology that precisely generates complex geometries from CAD files. Mechanical behavior of printed parts is greatly affected by printing parameters and defining the optimal values of the process parameters to enhance the mechanical properties of components is highly regarded. In this work, four different SLM parameters including scanning speed, laser power, hatch spacing and scan pattern angle were applied to manufacture SS316L parts. For investigating the effect of each parameter and their interactions on hardness and relative density, Taguchi L16 orthogonal array was employed. The influence of part geometry and remelting is also evaluated in order to optimize the hardness and relative density of components. The results exhibited that the laser scanning speed was the most predominant SLM parameter for investigated mechanical properties. Analyzing the regression formula obtained from the results showed that the optimum laser energy density resulted in a 0.37% and 5.38% increase compared to the lowest relative density and hardness, respectively. High remelting energy associated with low remelting scanning speed, caused an 8.5% and 17.9% rise in hardness of squares and triangles, respectively; however, it led 12.5% reduction in hardness for circles. Remelting caused a 2.32% reduction, 2.1% increase and 5.3% rise on relative density for circles, squares and triangles, respectively.