Investigating microstructural and mechanical property uniformity in 316L stainless steel alloys processed via laser powder bed fusion process

Additive manufacturing (AM) offers exceptional design flexibility and material efficiency, making it a critical technology in future aerospace, automotive, medical, and defense industries. However, achieving consistent mechanical properties across AM-processed parts remains a challenge due to anisotropy introduced by the layered printing process. This study investigates the microstructure and mechanical performance of laser powder bed fusion (L-PBF) processed 316L stainless steel alloys to assess uniformity and anisotropic behavior. X-ray diffraction (XRD), scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), and Energy Dispersive Spectroscopy (EDS) were employed to examine the phase composition, grain structure, grain misorientation, and elemental composition at different locations within the build volume. Mechanical properties were also evaluated through density, hardness, and tensile testing. The results show a high relative density (>99%) and consistent hardness (>220 HV) in all samples, demonstrating the effectiveness of the L-PBF process when parts are fabricated using optimized parameters. Tensile testing revealed higher yield strength (YS) and ultimate tensile strength (UTS) in horizontal and 45° builds compared to vertical builds due to reduced influence of interlayer defects. Fractography confirmed the presence of refined cellular substructures and ductile fracture with smaller dimples in horizontal and 45° builds, leading to improved mechanical performance. This study suggests that optimized parameters can achieve a high degree of phase homogeneity and reduce inherent heterogeneity in L-PBF-processed parts. It also highlights the importance of build orientation when designing components for applications demanding high tensile strength and reliability.