Numerical insights on the spreading of practical 316 L stainless steel powder in SLM additive manufacturing

In powder bed additive manufacturing (3D printing), powder spreading plays a dominant role in determining not only the subsequent process but also the quality/performance of the printed part. Therefore, how to realize a superior powder bed with desired structure and property is of key significance and has been the main concern for researchers and engineers, which needs more in-depth insights and understanding. In this article, the spreading process of 316 L stainless steel powder with continuous size distribution in practical SLM 3D printing was numerically reproduced by discrete element method. The effects of processing parameters on the macro- and microscopic properties of the spread powder beds were systematically investigated. Corresponding dynamics and mechanisms were analyzed. The results show that through comprehensive analyses, the optimal blade velocity and gap height of 0.01 m/s and 3 D (D90) are preferred for the superior powder bed with high packing density and good uniformity. The increasing particle flow instability and motion inertia caused by the high blade velocity as well as the serious wall effect and high jamming probability caused by the low gap height are the main reasons for the decline of the powder bed quality. [Display omitted] •Spreading of 316 L powder used in real SLM process is numerically investigated.•Quantitative macro/micro characterizations are conducted for quality evaluation.•Parametric effects are systematically studied to identify their role in spreading.•Mechanisms from particle motion, forces/stresses, and pore filling are analyzed.