Investigation of mechanical properties of 316 l steel samples at slm process with ultrasonic influence

The SLM process is characterized by high crystallization rates and the formation of columnar grain structures. In this work, two fiber lasers were used to reduce the characteristic grain sizes and improve the physical and mechanical properties of the synthesized samples during 3D printing with metal powder of 316 L steel. Along with a continuous ytterbium laser, a quasi-continuous-wave (QCW) laser was used, which varied the repetition rate and duration of signals. Absorption of pulses of the second laser in the near-surface layer of the melt pool led to generation of powerful short ultrasonic pulses in it and, as a consequence of their action, grain refinement in the formed structure of 316 L steel was observed. The average grain size at additional influence of QCW laser decreased from 50 μm to 25 μm. Mechanical testing showed that under certain QCW modes, the ultimate tensile strength increased by ~ 13-15% and the elongation at failure increased from ~ 34% to ~ 40%.