Enhancing Fatigue Performance of Additively Manufactured H13 Tool Steel through Surface Finishing Processes

Abstract

This study investigates the fatigue performance of additively manufactured H13 hot work tool steel (AM-H13 TS) produced using the laser powder bed fusion (L-PBF) process with two distinct build orientations: vertical (V-BO) and diagonal with 45° (D-BO). A fixed volumetric energy density of 57.3 J/mm3 was employed for fabrication. The study compares the as-built AMH13 TS to its surface-finished counterpart, focusing on fatigue life and damage under fully reversed tension-compression loading conditions. The surface finishing processes involved electropolishing using commercial DLyte 100HF+ equipment, followed by mechanical surface refinement. The surface topography and roughness characteristics of the as-built and post-polished specimens were comprehensively analyzed using laser confocal scanning microscopy (LCSM). Scanning electron microscopy (SEM) was utilized to examine the microstructural features and fatigue mechanisms. The as-built AM-H13 TS exhibited high surface roughness due to the presence of satellites and partially melted particles, which are inherent to the L-PBF process. The surface-finishing approach substantially mitigated these surface imperfections, resulting in significantly improved surface quality and reduced roughness. As a result, the fatigue performance of surface-finished AM-H13 TS showed remarkable enhancement. The fatigue limit increased fivefold, from 100 MPa in the as-built condition to 500 MPa after surface finishing. SEM analysis revealed that the improved fatigue strength was primarily attributed to the reduction in surface roughness and the elimination of surface flaws, which acted as crack initiation sites in the as-built condition.