Effect of 316L stainless steel powder size distribution on selective laser melting process

The product quality of selective laser melting (SLM) is closely related to the alloy powder size distribution. The small voidage of fine-sized alloy powder bed is beneficial to improve the density of SLM product. While, the fine-sized alloy powder would result in the poor powder spreading uniformity in the SLM equipment, which leads to the formation of holes in the SLM product. In this work, the 316L stainless steel powder was prepared by a vacuum atomization furnace and sieved into a coarse-sized distribution and a fine-sized distribution. Then, the coarse-sized powder and the fine-sized powder are mixed according to different ratios. The results show that, under the condition of same SLM parameters, the density and strength of the SLM sample gradually decrease, with the increasing amount of fine-sized powder. The main reason for this phenomenon is that the fine-sized powder, with the large specific surface, is easy to bond with the coarse-sized powder. It reduces the fluidity of powder, resulting in the pores and cracks during the SLM layering process. Furthermore, the addition of fine-sized powder to the coarse-sized powder results in a decrease in the elongation of SLM sample. However, with the increase of the addition amount of the fine-sized powder, the residual stress is released due to the formation of a large number of cracks and pores, so that the elongation of SLM sample is slightly increases.