Fabrication and Characterization of Porous 316L Stainless Steel Using Selective Laser Melting Technique for Biomedical Applications

Porous metals play essential roles in lowering the value of elastic modulus, achieving a modulus like that of the human body. Solid freeform fabrication has the potential to overcome the limitations of traditional manufacturing methods with controlled internal pore architecture. The use of 3D printing has been solely focused on polymer materials with limited investigations on producing porous metallic parts, such as implants. This research studies the influence of 3D printing on the pore architecture and its impact on cell growth. Selective laser melting (SLM), an additive manufacturing process, was used to fabricate 316L stainless steel porous structures. The stainless steel was selected for this research as a model system due to its known properties. Four cubic models of 15×15×4 mm^3 were designed using Autodesk inventor with interconnected pore sizes of 0.4 mm, 0.6 mm, 0.8 mm, and 1.0 mm. The CAD files were converted to STL models and then extracted into QuantAM software, which produces printing instructions for the Renishaw AM400 SLM machine. The results show that 316L stainless steel porous structures with fully interconnected pores were successfully fabricated using the SLM process, with a mean pore size reduction of 0.220 mm for all samples. The samples were subjected to an accelerated corrosion test for 336 hours using the salt spray chamber. 5 % wt. of NaCl formed part of the composition of the corrosive media, and by comparing the corrosion rates and weight loss of the interconnected structures, the samples experienced an insignificant percentage weight loss and an average corrosion rate of 3.0 mpy. The cell culture experiment reveals the cell growth viability of all samples of the selective-laser-melted 316L stainless steel structures seeded with Pseudomonas aeruginosa cells, for pore sizes ranging between 0.182 mm to 0.783 mm. The 0.783 mm porous structure with the highest porosity of 61.2% was most conducive to biofilm formation, allowing cell ingrowth into the pores