Experimental Investigation on Fabrication of Cermet Hollow Spheres for Use as Reinforcement in the Production of Lightweight and Strong Metal Foams for High Energy Absorption Applications

This study aims to develop lightweight and high-strength cermet hollow spheres from a blend of stainless steel (SS316L) and silicon-carbide (SiC) powders. The spheres can be used to manufacture high-energy absorbing materials like closed-cell metal foams if used as reinforcement in metals or metal-matrix composites (MMCs). Powder metallurgy method was used to fabricate the cermet hollow spheres of a diameter range of 7-9 mm and a maximum wall thickness of 0.5 ± 0.05 mm. A slurry was prepared using polyvinyl-alcohol solution and a mixture of SS316L powder with 5, 10 and 15% SiC powder with particle sizes of 40 µm. Expanded polystyrene balls (EPS) with diameters ranging from 5 to 8 mm were coated with the slurry, followed by dry coating and sintering at a temperature of 1250 °C for the steel and 1400 °C for the cermet to fabricate the hollow spheres. Compression strength testing was performed on a V-block block and a flatten plate setup incorporated with a universal testing machine (UTM). The strength of randomly selected hollow spheres varies from 100 to 125 MPa for the steel and 150-325 MPa for the cermet hollow spheres, showing the maximum value for the 10% SiC content. Fabrication and characterization of the steel and cermet hollow spheres are discussed in detail in this study.