Enhancing Wear Resistance of Selective Laser Melted Parts: Influence of Energy Density

Abstract

Selective laser melting (SLM) is a rapidly developing metal additive manufacturing technology. SLM process parameters have a direct impact on the microstructure of parts, which further affect wear behaviors. Increasing the wear resistance by tailoring process parameters, instead of postprocessing, is crucial for enhancing surface properties of the SLM-fabricated parts with complicated structures. In this study, 316L stainless steel samples were fabricated using different energy densities by varying hatch spacing and scanning speed. The relative density and hardness were measured, and the microstructures were examined. The wear resistance was evaluated by performing scratch tests. Results show that high hardness was found in the bottom region of the samples by small hatch spacings and the highest hardness of 302.8 ± 4.3 HV was measured in the sample by a hatch spacing of 10 μm. With the increase of energy density from 178 to 533 J/mm3 by reducing hatch spacing, the fraction of cellular structures decreases and columnar structures are more likely to be aligned in a relatively constant tilted angle from the build direction, which significantly improve the ability to resist slipping and deformation, indicated by 90.1%, 45.0%, and 15.7% reductions in wear rates under 1, 3, and 5 N, respectively. With the increase of energy density from 182 to 545 J/mm3 by reducing the scanning speed, the number of cellular structures increases but pores also form, which negatively affects wear resistance.