Effect of process parameters in the additive manufacturing of A2 tool steel

Abstract

Many process parameters may influence the integrity, microstructure and mechanical properties of Laser-based Powder Bed Fusion (L-PBF) samples. On an initial study of parameters optimization aiming for a process window that produces samples with the highest density and least number of defects possible, one may study the variation of Volumetric Energy Density (VED) and its influence on the densification of L-PBF samples. However, especially for high-strength alloys such as tool steels, the process may significantly reduce their ductility and promote crack formation during solidification due to the high thermal stresses involved. These stresses arise from the high cooling rates and thermal gradients inherent to the L-PBF. A significant amount of cracks were observed in A2 tool steel samples produced by L-PBF in a preliminary parameters optimization step. This BEPE project aims to tackle and resolve the problem of cracks formation in A2 tool steel by using substrate preheating to reduce thermal gradients and, consequently, thermal stresses. However, the equipment necessary to perform substrate preheating is not available at DEMa/UFSCar. Because of that, the student plans to use the equipment available at the Leibniz-Institut für Werkstofforientierte Technologien - IWT Bremen, a long-time partner of the student's research group. The duration of the BEPE is one year, during which samples will be produced using different substrate preheating temperatures and characterized by optical and scanning electron microscopy, X-ray diffraction and hardness. After this step of optimizing L-PBF parameters, samples will be produced for tensile tests to be carried out at the IWT-Bremen. (AU)