Influence of forming directions on surface quality of 316L produced by selective laser melting additive manufacturing

Abstract

Different forming directions have significant impact on surface quality in additive manufacturing. This study is aimed at exploring how different forming directions influence surface quality in additive manufacturing (AM). First, experiments were designed to prepare 316L stainless steel by selective laser melting additive manufacturing (SLAAM) in different forming directions. Moreover, the surfaces of samples manufactured by AM were tested using a three-dimensional (3D) surface profiler and a scanning electron microscope. Furthermore, the surface quality was characterized using four parameters, maximum height, S z ; maximum valley depth, S v; standard deviation of height, S q ; and arithmetic average height, S a. The following results were obtained: (a) different forming directions corresponded closely to upper surface roughness S a values, the values of S a being 7.16 and 8.20 μm, respectively. S a was the smallest among the four parameters; it showed good stability and statistical significance. (b) In the same forming direction, the upper surface roughness values followed the order S z > S v > S q > S a. S z was the largest, exceeding 800 μm; the average value S a was the smallest, reaching 7.36 μm. The values of S q , S z and S v vary when the forming direction changed. Specifically, all of them increased when the forming direction changed from a vertical direction to planar and lateral directions in turn. (c) In different forming directions, the values of S z , S v, S q and S a varied on different surfaces but their variations were basically similar. Meanwhile, the S z , S v, S q and S a values of the free surfaces were at least ten times greater than those of the printed surface. In the SLAAM process, it was necessary to select a forming direction reasonably for parts with different dimensional parameters on each side.