Isotropic Forming of Porous Structures via Metal Injection Molding

Porous 316L stainless steel structures have been fabricated via metal injection molding (MIM) for both water- and gas-atomized powders. The metal injection molding process offers the unique ability to produce net-shape parts with homogenous porosity, pore structure, and permeability. In this study, porous MIM structures were analyzed for porosity, pore size, permeability, and thermal conductivity as a function of powder type and processing conditions. A typical MIM powder (<20 µm) processed at 50 volume % loading in a binder system produced a uniform pore structure with a permeability of less than 1*10-13 m2 and a maximum pore radius of less than 5 µm . Water-atomized powder proved to be better suited for low-solids-loading metal injection molding (<50vol% loading) since its interparticle friction provided greater strength and fewer defects during the molding and debinding process steps. Measurements of thermal conductivity show that the water-atomized powder had less thermal conductivity (~2 W/m-K) than the gas-atomized powder (~3 W/m-K).