fabrication and properties of stainless-steel foams with simultaneous use of two different space holders

In this study, low-density yet high-strength 316l stainless steel foam was successfully fabricated using the powder metallurgy technique. this was achieved by employing both carbamide and steel hollow spheres as space holders to tailor porosity and mechanical properties. the volumetric percentage of carbamide was varied from 0 to 50% to investigate its effect on density, while steel hollow spheres (0%–50% by volume) were incorporated to enhance strength. the fabrication process involved layer-by-layer deposition of stainless steel powder and space holders in a mold, followed by uniaxial compaction at 150 mpa using polyvinyl alcohol as a binder. carbamide was removed through heat treatment at 120–180 °c in ambient conditions, and the samples were subsequently sintered at 1150 °c for 3 hours in a neutral atmosphere. following optimization of fabrication parameters and porosity control, the samples were characterized using compression tests and scanning electron microscopy (sem) to evaluate their mechanical performance and microstructural evolution. compression test results revealed that increasing carbamide content decreased the density, whereas a higher percentage of steel hollow spheres significantly improved compressive strength, reaching a maximum of 528.70 mpa at constant porosity. sem analysis confirmed that the replacement of carbamide with steel hollow spheres led to the transformation of open-cell porosity into closed-cell porosity.