Sibisi, THMathoho, IpfiShongwe, BSTshabalala, Lerato CSkhosane, Besabakhe SMotau, RMndebele, NVithi, N2026-06-292026-06-292026-062577-8196https://doi.org/10.1002/eng2.70785Digital Object Identifier (DOI)http://hdl.handle.net/10204/14832This study presents a comparative investigation of the microstructure and mechanical properties of AISI 5120 low-alloy steel fabricated using two Directed Energy Deposition (DED) systems: Laser Engineered Net Shaping (LENS) and robotic Direct Metal Deposition (DMD). The objective was to evaluate process–structure–property relationships under optimized operating conditions representative of each system. Microstructural characterization was performed using optical microscopy and scanning electron microscopy (SEM), while tensile strength, microhardness, and Charpy impact toughness were evaluated according to ASTM standards. The LENS-fabricated samples exhibited a predominantly ferrite–pearlite microstructure and demonstrated higher surface hardness (217 HV) and superior impact energy (137 J). In contrast, the DMD specimens displayed refined microstructural features with bainitic-like characteristics inferred from SEM morphology and achieved significantly higher tensile properties, including an ultimate tensile strength of 754.3 MPa, yield strength of 675.97 MPa, and elongation of 17.63%. Fractographic analysis indicated ductile failure modes in both systems; however, LENS samples showed a higher qualitative presence of porosity. The improved tensile performance of the DMD system is attributed primarily to reduced porosity and enhanced interlayer bonding resulting from higher energy input and improved melt pool stability. While LENS provided enhanced surface hardness and impact resistance, DMD demonstrated superior overall mechanical integrity. The findings highlight the importance of system-level process optimization when selecting DED platforms for load-bearing or wear-critical industrial applications. Further investigation including fatigue testing, quantitative porosity analysis, and phase confirmation using diffraction techniques is recommended.FulltextenDirected Energy DepositionLaser Engineered Net ShapingLENSDirect Metal DepositionAISI 5120 SteelMicrostructure–Property RelationshipMechanical propertiesArticlen/a