Individual and Coupled Contributions of Laser Power and Scanning Speed Towards Process-Induced Porosity in Selective Laser Melting

Porosity is an undesirable characteristic of selective laser melting (SLM) process and keyhole pores are formed when the energy density is very high which leads to deep penetration melting. In this study, single-track SLM experiments using Ti-6Al-4V powder were designed and conducted with combination of varied levels of the laser power and the scanning speed, intended to obtain the same energy density. Three energy densities: 0.32 J/mm, 0.4 J/mm and 0.48 J/mm were selected to investigate the influence of laser power versus scanning speed on porosity. Pore numbers and volumes was analyzed using micro-scale computed tomography. The results indicated that the pore formation is affected more by the change in the power than the scanning speed while keeping the energy density constant. As the power increased from around 20 W to 140 W, total pore volume increased, whereas pore volume decreased when power increased from 140 W to 195W.