Effect of microstructure and defect formation on the bending properties of additive manufactured H13 tool steel

Abstract

Due to its high strength and wear resistance and good fracture toughness at low and high temperatures, AISI H13 tool steel has been widely used to fabricate components such as injection molds, die casting dies, and hot forging tools. Components with complex geometries can be produced by additive manufacturing (AM); however, the success of this manufacture depends on the formed microstructure and mechanical properties, which are associated with the process parameters. The mechanical properties of H13 tool steel processed by AM reported in the literature are limited to those obtained through hardness and tensile tests. Thus, this study aims to correlate the bending properties of H13 tool steel with its microstructure and process parameters when processed by the Powder Bed Fusion (PBF) technique. The samples were produced with different energy densities (approximately 200, 400, and 600 J/mm³) and analyzed by XRD, OM, SEM, and ACOM-TEM. The amount of retained austenite in the cellular microstructure and the porosity decreased as the energy density increased. The sample manufactured with 400 J/mm³ presented the highest density and bending stress values. In contrast, the sample produced with 600 J/mm³ showed a smaller number of defects and more extensive deformation before fracture. This behavior was explained considering the fraction of retained austenite, intrinsic tempering, and presence of defects. The fracture mechanism comprised a mixture of cleavage and dimple formation. This study demonstrates that the bending properties of H13 tool steel processed by PBF are directly related to the resulting microstructure and process parameters used to fabricate the parts.