Laser Powder Bed Fusion of WS ₂ /316L Stainless Steel Nanocomposites for an Enhanced Mechanical and Tribological Performance

Implant materials and industrial components often face limitations due to wear and surface degradation, prompting the need for advanced materials with enhanced durability. This study investigates the development of 316L stainless steel metal matrix composites (MMCs) reinforced with tungsten disulfide (WS₂) nanoparticles (1, 3, and 5 wt %) fabricated via laser powder bed fusion (LPBF) to address these challenges. The incorporation of WS₂ leads to substantial microstructural refinement, transitioning the morphology to a finer, more equiaxed grain structure. While the 5 wt % WS₂ composites exhibit the highest surface roughness (1 μm), they also achieve superior mechanical properties, including the highest cross-sectional microhardness (254 HV) and a notable reduction in the hardness anisotropy between the top surface and the cross section. The tribological assessment under dry oscillating conditions reveals an exceptional efficacy of the 5 wt % WS₂ MMC. Compared to pure 316L, it demonstrates a 21% reduction in volumetric wear rate at 25 °C and a remarkable 44% reduction at 37 °C despite a higher coefficient of friction. Analysis of the underlying wear mechanisms indicates that the superior performance is attributable to a synergistic effect. The hardened subsurface resists plastic deformation, while the WS₂ nanoparticles form a protective tribofilm, reducing metal-to-metal contact. Raman spectroscopy confirmed the tribochemical formation of a WS₂-rich lubricious film at 25 °C and its evolution into a more complex, oxide-dominated protective layer at 37 °C, governing the transition to a tribofilm-controlled wear regime. The results underscore the potential of LPBF-fabricated WS₂/316L nanocomposites for creating high-performance, durable components for biomedical implants and industrial applications operating under demanding conditions.