The effect of hydrogen on gas porosity in Laser Powder Bed Fusion of AlSi10Mg

The density of components built using selective laser melting systems are greatly affected by pore formation during rapid solidification. By limiting the hydrogen content of the AlSi10Mg powder and the solidification through build parameters, gas porosity can be reduced. In this study, three types of porosity were characterized in AlSi10Mg samples built by both SLM and Concept Laser systems. Trends relating to energy input and pore type were established for gas, keyhole, and lack of fusion. The physical mechanisms for each type of pore formation were rationalized relative to solidification parameters such as, thermal gradient and solidification front velocity. Areal and volumetric density values were compared for samples built with specific techniques for eliminating hydrogen. The hydrogen content of both powders and builds were analyzed. This measured content confirmed the effectiveness of reducing gas porosity through process parameter control. Finally, the evolution of hydrogen concentrations is evaluated during solidification and the nucleation of gas pores is discussed.