Permeability and strength of a porous metal structure fabricated by additive manufacturing

This paper looks at the gas permeability of the porous structure of an injection-moulding die fabricated by selective laser sintering (i.e., additive manufacturing), and how this is affected by the laser conditions used. The metal powder used is a mixture of alloy steel, copper phosphorous and nickel powders with an average particle diameter of 25μm. A fibre laser (wavelength 1070nm) is used to consolidate the metal powder, thus making any differences in the consolidation of the metal powder strongly related to the energy density under which it is irradiated; varying from fully melted to a fully sintered condition with decreasing energy density. The permeability of compressed gases is found to increase with porosity, but no gas escapes when the porosity is below 6%. The tensile strength of the porous structure is also found to be related to its porosity, decreasing due to a combination of pores inside the structure.