Final properties of aisi 316l stainless steel produced by metal injection molding using sustainable natural rubber-based binder systems

Abstract Metal injection molding (MIM) requires binder systems capable of ensuring adequate flow behavior during molding while maintaining structural integrity throughout debinding and sintering. Although sustainable natural rubber-based binders have shown promising rheological performance, their influence on the final properties of sintered components remains insufficiently understood. In this study, AISI 316 L stainless steel feedstocks formulated with natural rubber-based binder systems were evaluated regarding solvent debinding behavior, densification, dimensional shrinkage, microstructure, quantitative pore characteristics, and Vickers microhardness after sintering at 1360 °C under a 95% N₂/5% H₂ atmosphere. Solvent debinding demonstrated that successful extraction depends on maintaining an appropriate balance between selective binder removal and backbone continuity. While feedstocks containing only natural rubber and carnauba wax remained structurally stable throughout debinding, the formulation containing polyethylene glycol at 60 vol% powder loading lost structural integrity and was excluded from the subsequent processing stages. Among the successfully processed feedstocks, the formulation containing 60 vol% powder loading and the natural rubber/carnauba wax binder system exhibited the highest relative density (91 ± 1%), the lowest pore area fraction and the finest pore-size distribution, and the highest Vickers microhardness. In contrast, increasing the powder loading to 62 vol% resulted in less efficient densification and greater pore heterogeneity. The microstructural observations were consistent with the densification behavior, demonstrating that processing stability during molding and debinding directly influences the final properties after sintering. Overall, the results demonstrate that natural rubber can successfully function as a backbone polymer in MIM binder systems, providing a sustainable alternative for producing 316 L stainless steel components. Although the obtained properties are within ranges reported in the literature for 316 L components produced using conventional binder systems, direct equivalence cannot be established because a conventional binder control was not included in the present study.