Experimental study of effects of main process parameters on porosity, track geometry, deposition rate, and powder efficiency for high deposition rate laser metal deposition

Laser metal deposition (LMD) is an additive manufacturing process. Although much research regarding effects of process parameters on deposition quality has been conducted in recent decades, the studies in this field are still lacking for high deposition rates (>0.3 kg/h) LMD. Most of the previous investigations were based on traditional LMD process, characterized by a low deposition rate (<0.3 kg/h). This paper presents a pilot study to find the answer on the effects of main process parameters on track dimensions and process characteristics in high deposition-rate LMD. Inconel 718 (IN718) powder was used as additive material. Chemical composition, porosity, shape, and morphology of the used powder were analyzed to ensure that the necessary specifications are met. Based on a high deposition-rate LMD process, which has a deposition rate of approximately 2 kg/h, experiments were designed and carried out on a dedicated high deposition-rate LMD experimental setup. Furthermore, effects of main process parameters (laser power, scanning speed, and powder mass flow) on porosity, track geometry, deposition rate, and powder efficiency were investigated. It is found that track porosity decreases with an increase of laser powder or a decrease of powder mass flow; the consistency of cross-sectional porosity is relative poor if laser powder is insufficient or powder mass flow is excessive. The transition between substrate surface and track surface becomes smoother with increasing laser power, increasing scanning speed or decreasing powder mass flow. Deposition rate and powder efficiency keep relatively constant after a significant increase with increased laser power until a certain threshold, but they are not correlated with scanning speed. Deposition rate increases whereas powder efficiency decreases with an increase of powder mass flow.