Microwave sintered SS316 porous foams from machining waste and their structure and energy absorption properties

Increasing demands for sustainable manufacturing are accelerating the need for efficient scrap reutilization routes that extend beyond conventional remelting practices. In this context, solid-state reuse of machining chips presents a viable pathway for producing high-value functional materials while supporting circular economy objectives aligned with UN SDG-12. This work reports a novel processing strategy for fabricating stainless steel 316 metallic foams directly from turning chips using microwave sintering. Consolidation was carried out at 1050 °C and 1200 °C under an argon atmosphere to suppress oxidation and contamination while enabling rapid and energy-efficient sintering. Three foam architectures: chip-based, hybrid and space-holder foams, were successfully produced and systematically characterized with respect to macrostructure, microstructure and compressive response. Foams sintered at 1200 °C exhibited a well-defined and stable stress plateau with enhanced energy absorption capacity. Their lower plateau stress facilitated progressive deformation under compressive loading, indicative of improved impact resistance. The results demonstrate that chip-derived stainless steel foams produced via microwave sintering offer strong potential for energy-absorbing and crash-relevant structural applications, while providing a sustainable route for high-value metal scrap reutilization.