Energy input effect on morphology and microstructure of selective laser melting single track from metallic powder

Process parameters of selective laser melting affect the response of a powder–substrate system and, therefore, the geometry and microstructure of the manufactured parts. The experiments were carried out at fixed values of laser power (50 W), spot diameter (70 μm) and powder layer thickness (80 μm). In this research, influence of the energy input parameters (80–900 °C preheating temperature and 0.08–0.28 m/s laser scanning speed) on microstructure and geometry of single tracks fabricated of stainless steel grade 316L powder was analysed. Both factors were found statistically significant with regard to their influence on the remelted depth and the primary cell spacing in the colonies observed in the tracks cross-sections. More specifically, the contact angle and track height were controlled by the preheating temperature, and track width and contact zone characteristics were governed by the laser scanning speed. Because of the threshold behaviour of these two factors, values starting with 700 °C and 0.24 m/s were found not optimal and causing instability and balling effect. Conclusions regarding the selection of process parameters for the formation of tracks with the desired geometry and microstructure were formulated based on statistical analysis of the experimental data.