Stainless Steel Hollow Sphere Foams-Fabrication, Carburization, and Properties

摘要

Lightweight stainless steel foams approaching 10% theoretical density are being fabricated via direct reduction. These foams are formed using a coaxial nozzle process that generates hollow ceramic spheres at high rates from an acetone-based slurry. The Fe2O3/Cr2O3 hollow spheres are reduced in a hydrogen/argon atmosphere at high temperature resulting in individual hollow metal spheres. Using more viscous slurry of similar composition, the spheres are bonded at points of contact into a quasi-closed cell structure and further heat treated to reduce the bond phase. The result is a Fe-12Cr alloy hollow sphere foam with a density on the order of 1 g/cc. Addition of carbon and further heat treatments allow the control of strength and ductility through micro structure. Mechanical testing is being conducted to determine attainable properties that can be compared to existing foam models.