The Influence of Boron Nitride(BN) Additives on the Microstructure and Mechanical Properties of 316L Stainless Steel Processed via Selective Laser Melting

Metal Additive Manufacturing (AM) has transformed the production of metallic components by enabling the fabrication of complex geometries with exceptional precision. Among the available AM techniques, Laser Powder Bed Fusion (L-PBF) is one of the most widely adopted, offering not only high dimensional accuracy and design flexibility but also the possibility of developing novel alloys and metal matrix composites. AISI 316L stainless steel is frequently processed by L-PBF due to its excellent corrosion resistance and ductility. However, its relatively low hardness and limited wear resistance restrict its use in more demanding applications. To overcome these limitations, this study explores the incorporation of hexagonal boron nitride (BN) as a reinforcing phase to tailor the microstructure and enhance the mechanical properties of L-PBF 316L parts. Microstructural analysis conducted through optical microscopy (OM) and scanning electron microscopy (SEM) revealed distinct changes in grain morphology and the occurrence of solidification cracks, largely associated with the rapid cooling inherent to the L-PBF process. Phase composition and secondary phases were identified by X-ray diffraction (XRD), while X-ray computed tomography (XCT) was employed to evaluate internal porosity and subsurface defects. Mechanical characterization demonstrated that BN reinforcement leads to a notable improvement in performance. Nanoindentation hardness increased by approximately 20% from a baseline of 5.01 GPa, while microhardness improved by about 15% from 210 HV. These results indicate that BN addition is an effective approach for strengthening L-PBF 316L stainless steel and improving its durability in demanding service conditions.