Metal additive manufacturing (AM) technologies can be classified according to the physical process involving the raw material as fusion-based and solid-state processes. The latter includes sintering-based technologies, which are aligned with conventional fabrication techniques, such as metal injection molding (MIM), and take advantage of the freeform fabrication of the initial green part. In the present work, 17-4PH stainless steel samples were fabricated by material extrusion, or rather bound metal deposition (BMD), a solid-state AM technology. The powder-based raw material was characterized together with samples fabricated using different angular infill strategies. By coupling different characterization technologies, it was possible to identify and classify major properties and defects of the raw material and the fabricated samples. In addition, microstructural modifications were found to be linked with the mesostructural defects typical of the BMD solid-state additive manufacturing technology applied to metals.

The dislocation density in additive-manufactured components significantly influences the local mechanical behavior of crystalline metals. Nanoindentation, renowned for its sensitivity to local mechanical responses and hardness, facilitates the assessment of local dislocation density. This study aimed to analyze the evolution of local dislocation densities in bulk, graded lattice structures (GLSs), and reduced-size GLSs of LPBF SS316L via nanoindentation. Components were fabricated using laser powder bed fusion with 316L stainless steel. The microstructural analysis revealed that the distribution of mechanical deformation across the bodies of the parts was higher in the reduced-size GLS compared to that obtained for the GLS. The simulation of plastic deformation allowed for recognizing that this difference is attributed to the different thermal stresses resulting from the higher rate of thermal excursions to which the scaffold structure was subjected whenever there was a reduction in the reciprocal distance of the struts. Mechanical deformation, identified as the primary factor contributing to dislocation density in additive manufacturing, was significant in both the GLS and reduced-size GLS, for which the dislocation density was incremented by one order of magnitude compared to the bulk material.

Metallic mechanical metamaterials have attracted the attention of many industrial sectors due to their unique properties which enable them to outperform natural materials in unconventional ways. Metal metamaterials encompass multiple fields, including materials science, mechanics, and industrial technology, and they have become particularly popular following the implementation of reliable, high-resolution, efficient metal additive manufacturing processes. This review takes a joint approach, providing an in-depth analysis of the base materials and geometries that characterize metamaterials in order to understand their behavior in response to impacts at different load regimes and to offer readers a critical overview of the most suitable design choices for energy absorption systems. Furthermore, this review highlights advanced metamaterial optimization methods that are useful for increasing the mechanical energy absorbed avoiding peak impulse transfer to the people, instrumentation, or generic loads that mechanical metamaterials are designed to protect.

This study explores the application of lattice structures as internal support architectures in the fabrication of Inconel 718 components via Laser Powder Bed Fusion (L-PBF), building upon previous research on beam-based FCCZ supports. Two representative lattice typologies were investigated: the node and beam-based FCCZ (face centered cubic with Z direction reinforcement struts) structure and the triply periodic minimal surface (TPMS) Schoen Gyroid cell. The aim was to assess how the transition from a discrete beam-node architecture to a continuous surface topology influences manufacturability, thermal stability, and mechanical performance. Finite Element Method (FEM) simulations in Ansys accurately predicted distortions and residual stresses during the L-PBF process, showing strong agreement with stereomicroscope measurements. Specifically, the maximum directional deformation reached 0.32 mm for the FCCZ sample versus 0.17 mm for the Gyroid, with corresponding peak residual stresses of 1328 MPa and 940 MPa, respectively. After fabrication, the samples underwent solution treatment and double aging according to AMS 2774 and AMS 5662 standards. Vickers microhardness increased from about 320 HV0.3 in the as-built condition to 500 HV0.3 after heat treatment (+55%), with overall porosity remaining below 1%. Microstructural analysis using optical microscopy (OM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) revealed that heat treatment partially homogenized the microstructure but did not achieve complete recrystallization, leaving localized dendritic regions and undissolved Laves phases, particularly near the lattice. The precipitation of γ′ and δ phases enhanced hardness and mechanical uniformity, as confirmed by Vickers microhardness testing. Quantitatively, the Gyroid topology exhibited approximately 40% lower deformation and defect density than the FCCZ structure, confirming its superior manufacturability and thermal stability. These findings provide practical guidance for selecting lattice topologies for support architectures in L-PBF Inconel 718 components where thermal stability and shape preservation during build are critical.

Nickel-based coatings have been demonstrated to effectively enhance the surface performance of stainless-steel components. The present study investigates the deposition efficiency and quality of Colmonoy 227-F nickel alloy coatings on AISI 304 stainless steel using direct energy deposition (DED). The work focuses on the relationships between process parameters, microstructural features, and mechanical properties. A total of sixteen process parameter combinations were studied, varying laser power and scanning speed to establish optimal deposition conditions and to evaluate coating morphology, surface topology, dilution behavior, and mechanical performance. The surface geometry was analyzed using three-dimensional digital confocal microscopy. New material distribution (MD) indices were developed to quantify spatial uniformity and integrity of single coating scan tracks (CSTs) across the XY, XZ, and YZ planes. The optimal process was identified around 900 W laser power, balancing deposition efficiency and structural integrity. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) reveal a gradual compositional transition between coating and substrate. The results of the microhardness test demonstrate a consistent gradient in mechanical properties, extending from the coating to the substrate. Coatings were found to achieve a hardness level of up to 600 HK. These findings establish a new benchmark for evaluating DED high-performance coatings and offer a scalable methodology for optimizing additive manufacturing processes in surface engineering applications.