Multi-Objective Optimization of SLM Parameters for SS316L: Surface Quality, Microhardness, and Tribological Assessment

Austenitic stainless steel 316L (SS316L) is used in orthopedic and dental implants, surgical instruments, and aerospace fluid-handling components because of its corrosion resistance and ductility. Selective Laser Melting (SLM) produces these parts with internal channels that casting and machining cannot deliver. However, as-built SS316L surfaces contain spatter, partially fused powder, and near-surface porosity that raise roughness and reduce fatigue strength, corrosion resistance, and wear performance. Producing parts that meet both surface and mechanical requirements in a single build remains difficult. This study examines how laser power, scanning speed, layer thickness, and hatch spacing affect the surface roughness, microhardness, and wear of SLM-fabricated SS316L. A Box–Behnken Design under Response Surface Methodology (RSM) was used for 27 experimental trials. Surface roughness was measured by stylus profilometry, microhardness by Vickers indentation, and dry sliding wear with a block-on-disc tribometer. Regression analysis and multi-response desirability optimization were carried out in Minitab. Processing parameters showed clear effects on surface quality and hardness; the wear response varied considerably because of localized surface defects and particle adhesion. Multi-objective optimization gave a composite desirability of 0.7603 at 260.6 W, 507.1 mm/s, 41.9 μm, and 120.0 μm. The predicted upper surface roughness, side surface roughness, and microhardness were 5.74 μm, 13.63 μm, and 210.39 HV, respectively. Run 26, tested at a volumetric energy density (VED) of 125.0 J/mm3, recorded an upper surface roughness of 5.48 μm and a microhardness of 218.1 HV. Surface defects strongly influenced the sliding response. The study provides a practical RSM-based route for selecting SLM parameters that balance surface quality and microhardness in SS316L components.