Direct Laser Deposition (DLD) is a form of metal-based additive manufacturing. The DLD process involves ejecting powder out of a nozzle by means of an compressed gas and irradiating a laser beam to heat up the powder and the substrate. During the powder spray ejection, tight focusing of the powder stream has the potential to improve the DLD process by reducing powder wastage. Thus, nozzle design and computational fluid dynamics (CFD) analysis of the design parameters become important. This study focuses on the numerical simulation of the gas-solid flow inside a coaxial DLD nozzle and how design features of the nozzle affect powder focusing. The two-phase gas/powder flow was analyzed using a Eulerian-Lagrangian scheme. A total of twelve designs were simulated and analyzed through CFD simulation, with features such as inlet angle, inlet offset, and the presence and shape of flow-straightening grooves considered. It was determined that geometry reducing particle tangential velocity such as flow-straightening grooves produce the best focusing effects, whereas offset inlets without the presence of grooves reduces focusing by maximizing particle swirling. Finally, the simulations show that the distribution of powders within the nozzle is also affected by nozzle inlet angle, with horizontal inlets providing more even distribution over inlets angled towards the nozzle tip.

Cold sprayed polymer substrates offer a promising platform for bridging electroless deposition methods and applications. This study’s contribution to the field is the combination of cold sprayed polymer substrate and the electroless-plating process. In simulation, finite element analysis of the as-sprayed polymer substrate using a viscoelastic model that considers large strain time-dependent behavior were conducted. A three-network constitutive model was applied to capture the non-linear and time-dependent response of large strain polymer deformation. In experiment, the process-structure-property relationship was examined from the as-sprayed specimen to the final coated electroless-plated samples. A controlled coating process of Cu powders was first cold sprayed on polyamide 6. The as-sprayed specimen was then electroless deposited. Mechanical testing was performed on as-sprayed specimens and adhesion testing was performed on electroless deposited specimens. Scanning electron microscopy (SEM) was employed to observe the surface and the cross-section of the as-sprayed and electroless deposited specimens. Lastly, the behavior of Cu coated specimens immersed in KOH solution was examined by cyclic voltammetry.

Previous studies have shown that metallic coatings can be successfully cold sprayed onto several polymer substrates. The electrical performance of the cold-sprayed polymers, however, is not generally sufficient enough to utilize them as an electronic device. In this paper, an environment-friendly metallization technique has been proposed to fabricate conductive metal patterns onto polymer substrates combining cold spray deposition and electroless plating to address that challenge. Copper feedstock powder was cold sprayed onto the surface of the acrylonitrile-butadiene-styrene (ABS) parts. The as-cold sprayed powders then served as the activating agent for selective electroless copper plating (ECP) to modify the surface of the polymers to be electrically conductive. A series of characterizations are conducted to investigate the morphology, analyze the surface chemistry, and evaluate the electrical performance and adhesion performance of the fabricated coatings. After 6 hours of ECP, the sheet resistance and resistivity of copper patterns on the ABS parts were measured as 2.854 mΩ/sq and 6.699 × 10 −7 Ωm respectively. Moreover, simple electrical circuits were demonstrated for the metallized ABS parts through the described method. The results show that low-pressure cold spray (LPCS) and ECP processes could be combined to fabricate electrically conductive patterns on ABS polymer surfaces in an environmental-friendly way.