Production and characterization of lattice samples with solid shell in 17-4 PH stainless steel by Laser Powder Bed Fusion technology

In this work, 17-4 PH stainless steel square-based lattice structures with solid shell were manufactured by Laser Powder Bed Fusion. Face Centered Cubic unit cell was chosen as lattice cell geometry. The main aim of this work was to study the role of the shell in the mechanical behavior under compression load and to identify any critical issue due to the connection of the shell with lattice part. This is a relevant topic since often lattice structure are integrated with solid walls and the study of the relative behavior can support the understating of the performance of complex components. The manufactured samples were tested in as-built and heat-treated condition. In detail, solution and aging treatment was performed as a conventional route for 17-4PH steel. In particular, microhardness and compressive tests were performed, and the mechanical behavior and the fracture mechanisms of the samples were investigated. Furthermore, the defects, the geometry of the struts and the connection with the solid part were analyzed. The detachment of the shell from the lattice did not occur. In fact, the solid part followed the deformation of the structure. The microstructural evolution after heat treatment was found to be responsible for an increase in hardness, strength and deformation for the investigated structures.