Permeability of Additive Manufactured Cellular Structures—A Parametric Study on 17-4 PH Steels, Inconel 718, and Ti-6Al-4V Alloys

Abstract

Cellular structures of metallic alloys are often made for various industrial applications by additive manufacturing. The permeability for fluid flow in these cellular structures is important. The current investigated the gas fluidity of cellular structures made by selective laser melting (SLM). The porosity and permeability of the SLM cellular structures were measured for 17-4 PH stainless steel, Inconel 718, and Ti-6Al-4V alloys. The relations between porosity and energy density are expressed using the power law. The characteristic molar energies were 1.07 × 105, 9.02 × 104, and 7.11 × 104 J/mole for 17-4 PH steel, Ti-6Al-4V, and Inconel 718 alloys, respectively. 17-4 PH steel gave rise to higher porosity at the same energy density when compared with Ti-6Al-4V and Inconel 718 alloy. The values of these molar energy density are related to the heat needed to melt the alloys, viscosity, and thermal conductivity. It was further shown that air permeability is not only concerned with the percentage of porosity in the cellular materials, but it also relates to the tortuosity of pore pathways formed in the cellular materials. At the same porosity, Inconel 718 demonstrates higher air permeability in comparison with that of Ti-6Al-4V and 17-4 PH alloys due to its smoother pore pathways. Ti-6Al-4V, on the other hand, demonstrates the highest specific surface areas due to powder sticking along the pore pathways and led to the lowest permeability among the three alloys.

Keywords

• powder bed fusion
• selective laser melting
• energy density
• cellular structures
• permeability
• 17-4 PH