Optimization of surface quality and shell porosity in low carbon steel hollow spheres produced by powder metallurgy

Metallic Hollow Spheres (MHSs) as a base material in production of hollow sphere structures and developed composite metal foams are produced using an advanced process based on powder metallurgy. In this study, polystyrene spheres were coated with a gas and water atomized iron powder with particle size distributions of 1–5 μm and 20–25 μm, respectively. The green spheres were heat-treated to remove the binder at 600 °C with a heating rate of 50, 100 and 600 °C/min, and then the process was followed by sintering at various temperatures of 1100, 1140 and 1180 °C. Results show that an optimum output is attainable applying coarser particles and a higher sintering temperature, where the shell porosity is low enough and the sphere shells remain intact.