Effects of Pulsed Laser Repetition Rate and Duty Cycle on Heat-Affected Zone Narrowing in Laser Powder Bed Fusion of 316L Stainless Steel

Laser Powder Bed Fusion (L-PBF) is a type of metal additive manufacturing process. It has attracted increasing interest over the past few decades. L-PBF systems typically use continuous wave (CW) emission. Recently, pulsed wave (PW) emission has been introduced in order to have better control of the heat-affected zone (HAZ) and potentially enhance spatial resolution. Generally, the PW emission involves the laser temporal profile that can be modulated by such as pulse durations, duty cycles, and pulse repetition rates (PRR). Nevertheless, based on a literature survey, the systematic investigation of pulsed wave (PW) emission in the L-PBF process, which changes the laser temporal profile by adjustment of the pulsed laser parameters has scarcely been examined. The determination of suitable pulsed laser parameters needs to be employed in order to achieve these good attributes of PW emission to obtain the final part with high quality. Hence, this work investigates the effects of modifying the pulsed laser parameters on single track formation in AISI 316L pulsed L-PBF using numerical simulation with Flow-3D AM Software. The simulation cases used different pulse durations, duty cycles, and pulse repetition rates (PRR) while the layer thickness, scanning speed and laser power were kept constant. The key results demonstrate that increasing the PRR by four times while maintaining a constant Linear Energy Density (LED) reduced the width of the 700 K isotherm HAZ by 7%, highlighting the role of PRR in minimizing thermal diffusion. Furthermore, increasing the duty cycle while keeping the PRR and pulse period constant resulted in a smoother surface finish, as evidenced by a reduction in surface roughness (Ra) to less than 4 µm, compared to typical Ra values of 5–12 µm in CW L-PBF systems. This change also resulted in a wider HAZ, emphasizing the trade-off between surface finish and thermal diffusion. The findings from this study provide insights for optimizing processing parameters in L-PBF with PW emission, enabling the production of parts with finer geometries and enhanced surface quality.