Microstructural Evolution and Mechanical Enhancement of ۳۰۴L Stainless Steel Fabricated by Selective Laser Melting

This study investigates the influence of Selective Laser Melting (SLM) on the microstructure, mechanical properties, and hardness of ۳۰۴L stainless steel (۳۰۴L SS) in comparison with cast ۳۰۴L. SLM samples were fabricated from spherical powders with an average particle size of approximately ۳۰ μm, resulting in a distinct melt pool microstructure and a ۵۲% reduction in grain size compared to the cast sample. X-ray diffraction confirmed the retention of a single-phase austenitic structure, while dislocation density increased from ۱.۷ × ۱۰¹⁵ m⁻² to ۳.۳ × ۱۰¹⁵ m⁻² in the SLM sample due to rapid solidification and steep thermal gradients. Mechanical testing revealed that the SLM-۳۰۴L exhibited ۳۳% higher yield strength and ۲۷% higher ultimate tensile strength while maintaining a high fracture strain of ~۳۸%, demonstrating an effective combination of strength and ductility. Additionally, Vickers hardness increased by approximately ۳۲% compared to the cast sample. These results demonstrate that SLM enables the fabrication of ۳۰۴L SS components with enhanced mechanical performance through microstructural refinement and defect engineering, offering a promising alternative to conventional casting for high-performance applications.

Keywords:

selective laser melting (SLM) , additive manufacturing , ۳۰۴L stainless steel , microstructural evolution , mechanical properties