Synergistic Effect of Pre-Aging and Nitriding on the Microstructure and Wear Resistance of L-PBF Manufactured 18Ni300

Additively manufactured maraging steel components often require surface engineering to achieve superior wear resistance for demanding industrial applications. This study investigates 18Ni300 maraging steel manufactured by Laser Powder Bed Fusion (L-PBF), comparing non-aged and pre-aged (480 °C × 6 h) specimens to systematically analyze the effects of nitriding duration (0 h, 24 h, 48 h, 60 h) on nitride layer microstructure, hardness, and wear resistance. Results show that the non-aged specimen, with its supersaturated solid solution matrix, exhibits slower nitride layer growth; a thin, dense nitride layer formed after 24 h of nitriding minimizes the wear depth (−9.043 μm) for optimal friction reduction. In the pre-aged specimen, matrix refinement, through intermetallic compound precipitation, enables a 211 μm nitride layer to form after 48 h of nitriding, elevating surface hardness to 650 HV, and creating a gradient structure (“high-hardness surface + strengthened matrix”), which yields the narrowest and shallowest wear scars and superior wear resistance. The experiments demonstrate that nitriding processes must align with matrix states; 24 h nitriding suits non-aged steel, while 48 h is optimal for aged steel, providing critical guidance for optimizing surface strengthening in additively manufactured 18Ni300 steel.