Metal Deposition Process Research Articles

Hybrid Path Generation Method for Multi-Axis Laser Metal Deposition of Overhanging Thin-Walled Structures.

Additive manufacturing has advantages over other traditional manufacturing technologies for the fabrication of complex thin-walled parts. Previous correlation path strategies, when applied to laser metal deposition processes, suffer from contour deposition transboundary and surface "scar" type overstacking. Therefore, this paper proposes a hybrid path generation method for the laser metal deposition process. First, the topological logic of the STL model of the part is restored to reduce redundant calculations at the stage of obtaining the layered contour. Then, the path points are planned on the basis of the offset contours in a helical upward trend to form a globally continuous composite path in space considering the melt channel width. Finally, vectors that adaptively fit to the model surface are generated for the path points as tool orientations and they are optimized by smoothing the rotation angles. The results of experiments conducted on a multi-axis machine equipped with a laser metal deposition module show that the path generated by the proposed method is not only capable of thin-walled structures with overhanging and curved surface features but also improves the surface imperfections of the part due to sudden changes in the angle of rotation while ensuring the boundary dimensions.

Reducing Oxidation during Direct Metal Deposition Process: Effects on Ti6Al4V Microstructure and Mechanical Properties

The production of materials with a high affinity for oxidation using the direct metal deposition (DMD) process requires an extended process examination that goes beyond the usual, purely energetic consideration, with the aim of providing sufficient energy to melt the substrate and the powder material supplied. This is because the DMD process does not allow any conclusions to be drawn as to whether it and its respective selected parameters result in an oxidation critical process. To assess this, a superposition of the temperature field with the existing spatial oxygen concentration is required. This work uses this approach to develop an oxidation model that reduces oxidation during the DMD process. In addition to the numerical model, an analytical model is derived, with which the temperature of a material element can be calculated analytically and the resulting boundary oxygen concentration calculated using Fick’s 2nd law. The model also takes into account two-stage oxidation kinetics for Ti alloys. The effect of too high a travel speed (with the same specific energy of the other experiments) is shown visually in the numerical calculation of the temperature field. However, if the process model is taken into account, the components do fulfil the specified requirements. Finally, the effect of oxidation on the microstructure, microhardness, ultimate strength, yield strength and elongation at failure of Ti6Al4V structures produced using DMD is also investigated, and further supports our conclusions regarding the effectiveness of the proposed model.

Electroless silver plating combined with laser direct writing technology: For the fabrication of flexible silver mesh transparent electrodes

Ultra-thin metal meshes are emerging as potential candidates for ln2O3 (ITO) due to their mechanical properties, excellent flexibility and optoelectronic properties. However, the manufacturing of high-performance metal meshes is often accompanied by thin-layer metal deposition processes such as sputtering deposition and vacuum evaporation, as well as the combination of imprinting templates, which increases the complexity of the process and production costs. Herein, we have established a finite element theoretical calculation model for predicting the optoelectronic performance of metal meshes and propose a method based on electroless plating silver combined with laser direct writing to prepare high-quality Ag meshes. It provides a way to achieve rapid and economical production of Ag mesh transparent electrodes. The ultra-thin Ag mesh exhibits excellent transmittance (90.2 % at 550 nm), the transmittance is close to 95 % above the 600 nm wavelength band and the sheet resistance is 13.0 Ω/sq. Furthermore, The Ag mesh exhibits excellent mechanical flexibility, indicated by the fact that the resistance is almost unchanged after 5000 bending cycles.

Welding of additive manufacturing AlSi10Mg alloys using a laser metal deposition process with different heat inputs

Welding of additive manufacturing AlSi10Mg alloys using a laser metal deposition process with different heat inputs

Effect of Quasi-One-Dimensional Properties on Source/Drain Contacts in Vertical Nanowire Field-Effect Transistors (VNWFETs).

In this study, we investigated the influence of quasi-one-dimensional (Quasi-1D) characteristics on the source and drain contact resistances within vertical nanowire (NW) field-effect transistors (FETs) of diminutive diameter. The top contact of the NW is segregated into two distinct regions: the first encompassing the upper surface, designated as the axial contact, and the second encircling the side surface, known as the radial contact, which is formed during the top-contact metal deposition process. Quantum confinement effects, prominent within Quasi-1D NWs, exert significant constraints on radial transport, consequently inducing a noticeable impact on contact resistance. Notably, in the radial direction, electron tunneling occurs only through quantized, discrete energy levels. Conversely, along the axial direction, electron tunneling freely traverses continuous energy levels. In a meticulous numerical analysis, these disparities in transport mechanisms unveiled that NWs with diameters below 30 nm exhibit a markedly higher radial contact resistance compared to their axial counterparts. Furthermore, an increase in the overlap length (less than 5 nm) contributes to a modest reduction in radial resistance; however, it remains consistently higher than the axial contact resistance.

Experimental study of SS316L, Inconel 625, and SS316L-IN625 functionally graded material produced by direct laser metal deposition process

Three types of walls were produced by the direct laser metal deposition (DLMD) process; SS316L, Inconel 625 (IN625), and SS316L-Inconel 625 FGM. The thin walls were deposited on an AISI 4130 austenitic steel substrate in five layers with a length of 2 cm. The solidification behavior, secondary dendrite arm spacing (SADS) value, chemical composition, and hardness of samples were studied. Microstructures were evaluated using optical microscopy (OM) images, scanning electron microscopy (SEM), EDS Line, EDAX, and Map analyses. OM and SEM images showed an acceptable bonding between the layers in all samples. The main solidification was equiaxed dendritic and columnar dendritic in most parts. The growth of dendrites was perpendicular to the substrate. Some dendrites grew epitaxially at the interface of two sequential layers. The standard deviation of SDAS value for SS316L, IN625, and SS316L-IN625 FGM was 0.63, 0.71, and 0.73, respectively. The lowest value of SDAS was obtained in layer one, while the highest value was obtained in layer five of the thin walls. The average SDAS values for SS316L, IN625, and SS316L-IN625 FGM were 4.40, 4.53, and 4.76 µm, respectively. Therefore, the difference between the SDAS values was not significant. EDAX and Map analyses showed that the segregation of Nb and Mo to the dendritic boundary and the formation of eutectic, secondary phases, and brittle Laves phases have occurred. Additionally, the segregation of Nb and Mo to the dendritic boundary in the SS316L-IN625 FGM sample was higher than SS316L and IN625 samples. The microhardness values oscillated significantly and decreased by moving away from the substrate (in the build direction). The microhardness values of different points of the SS316L-IN625 FGM walls were in the range of 218–278 HV. EDS line scan, microstructure, and microhardness analyses indicated the successful fabrication of the SS316L-IN625 FGM by the DLMD process.

High-sensitivity dual U-shaped PCF-SPR refractive index sensor for the detection of gas and liquid analytes.

A dual U-shaped photonic crystal fiber (PCF) biochemical sensor based on surface plasmon resonance (SPR) is designed for the simultaneous detection of gas and liquid analytes, and the properties are analyzed by the full vector finite element method (FEM). SPR is excited by placing gold nanowires on the inner surface of the U-shaped device. In this technique, the traditional metal deposition process can be replaced, subsequently reducing the difficulty and complexity of actual production and improving the phase matching between the basic mode and plasmonic modes. To improve the detection properties, the structural parameters of the sensor including the air hole diameter, spacing, gold nanowire diameter, and polishing depth are optimized, and to better evaluate and analyze the sensing properties, the wavelength and amplitude modulation inquiry method is adopted. The results show that the maximum wavelength sensitivity (WS), amplitude sensitivity (AS), minimum resolution (R), and optimal FOM are 35,000nm/RIU, 438.08R I U -1, 2.86×10-6 R I U, and 165.16R I U -1, respectively. In addition, the sensor can detect analyte RIs between 1.00 and 1.36 for gas and liquid analytes simultaneously. Owing to the simple structure, low cost, and ambient-condition monitoring, the sensor has large potential in a myriad of applications including sewage treatment, food safety, humoral regulation, environmental and biological monitoring, and medical diagnosis.

A review of energy efficiency and Machine learning analysis for additive manufacturing of direct laser metal deposition

Additive Manufacturing (AM) is an innovative industrial process that utilizes layering of materials to create unique products with an unprecedented level of flexibility. To maximize the benefits of AM, it is crucial to understand the precise utilization of laser energy. This review provides a concise overview of the Directed Laser Metal Deposition (DLMD) process, which includes an analysis of input parameters and the effective use of laser power, along with the impact of laser synchronous preheating processes. Various input parameters such as travel speed, hatch spacing, powder feed rate, and the standard of distance influence the calculation of volumetric energy density (VED). VED is important for Clad bed geometry, including dilution (D), height (H), width (W) of AM wall, and clad bead stability (ΔH). In the field of manufacturing, Machine Learning (ML) is a commonly used subset of Artificial Intelligence (AI) to improve the quality of processes, expedite production, and reduce costs. Specifically, in Metal Additive Manufacturing (MAM), ML techniques are leveraged to optimize various process parameters, resulting in the production of high-quality, defect-free products. This review provides a detailed explanation of the step-by-step implementation process of ML and its classification within a fundamental structure.

The dynamic carbon footprint modeling for laser direct metal deposition based on processing states

The Laser Direct Metal Deposition (LDMD) process offers notable advantages and obtains wide application in aerospace, defence equipment and other industrial sectors. However, the characteristics of multiple-inputs and low-efficiency in the process will bring about high carbon footprint. Additionally, the carbon footprint fluctuates with processing states and equipment systems owing to the discontinuous process in LDMD involving the layer-by-layer deposition and the laser-powder coupling. This paper investigated dynamic carbon footprint based on the resource and energy consumption from the process-oriented standpoint in LDMD process, which quantified the processing time, power distribution and material consumption of each processing state for every sub-system. In this research, the discontinuous process was divided into effective processing state, rapid moving state and transformed delay state and the processing time of each state were estimated with process parameters. Besides, the operating state time and power distribution of five sub-systems were estimated combining the equipment triggering mechanism and the processing state time. The orthogonal experiment was carried out to deposit the 316L stainless steel powder into parts with the size of 15 mm*15 mm*10 mm under the given process parameter conditions (Vf ∈ [8,12] g/min, P ∈ [600,1000] w, Vs ∈ [500,900] mm/min). The results show that carbon footprint of deposited parts fluctuates in the range of 3624.68–15759.08 g under parameter combinations and the low carbon footprint parameter-interval is obtained. The average carbon footprint of effective processing state, the transformed delay state and the rapid moving state account for 55%, 40% and 5% respectively, while the carbon footprint of powder supply sub-system contributes to 68% among the five sub-systems. This research revealed and qualified the dynamicity of carbon footprint at the levels of processing states, process parameters and sub-systems, offering potential for carbon footprint reduction in advanced manufacturing processes.

Wear and Corrosion Resistant Eutectic High-Entropy Alloy Al0.3CoCrFeNiMo0.75 Produced by Laser Metal Deposition and Spark-Plasma Sintering

Eutectic high-entropy alloys (EHEAs) with a fine-lamellar structure and homogenous property profile are of particular interest for wear and corrosion protection coatings. High cooling rates in the laser metal deposition (LMD) process can induce microstructure refinement and allow the formation of a supersaturated solid solution in EHEAs. A subsequent solution annealing can create the equilibrium state. In the present study, LMD coatings with an ultrafine-grained Widmanstätten structure were produced from the EHEA Al0.3CoCrFeNiMo0.75 gas atomized powder. High cooling rates during deposition led to a supersaturated solid solution with face-centered cubic (FCC) structure. The LMD coating exhibits the highest average hardness of 734 HV0.5, which drops to approx. 200 HV0.5 due to an increased microstructural domain size after heat treatment. Under oscillating wear, the formation of oxidized wear debris promotes material removal in the heat-treated condition. Corrosion tests reveal a deterioration of the passivation behavior. LMD processes exhibit great potential to create supersaturated solid solutions with refined structure in EHEAs to enhance the property profile.

Investigation of the Mechanical Characteristics of Metal 3D Printing at Different Build Orientation and Directions

Abstract In this paper, metal 3D printing technology was used to investigate the effects of build orientation angles and direction on the mechanical characteristics of 316L stainless steel produced by the Bound Metal Deposition (BMD) process. Several orientation angles (0 deg, 45 deg, and 90 deg) of the test specimens were made for both horizontal and vertical build directions. The tensile testing apparatus was used on metal 3D-printed samples to determine their mechanical characteristics, such as Young's modulus, elongation at break, and ultimate strength. Brinell hardness tester was also used to compare the hardness of 3D-printed samples to the original native material. In addition, the porosity and microstructure of the printed samples were analyzed in this study. The findings of this investigation revealed how, in comparison to the original material, the mechanical properties of the metal 3D-printed material rely on the raster orientation and build type. The experimental results demonstrate that the 3D-printed parts using the BMD process have comparable ultimate tensile strength and elongation at break compared to the original material for 0 deg orientation and horizontal build direction. The elongation at break was found to depend strongly on the build direction for 45 deg and 90 deg printing orientation. Further, Young's modulus was found to be much lower than the original material using the BMD process.

Oxygen Uptake of Ti6Al4V during Direct Metal Deposition Process

The efficient fabrication of titanium components using laser direct metal deposition (DMD) is gaining significant importance in the aerospace and medical sectors. The DMD process must be appropriately designed to address the issue of oxidation, as titanium exhibits a high affinity for oxygen. The carrier gas flow and shield gas flow, which have been considered secondary factors so far, are shown to exert a substantial influence on the gas dynamics of the DMD process. By varying these parameters, it is possible to identify the influence of the gas volume flows on the oxidation behavior exhibited during the DMD process. To quantify the oxygen uptake in titanium structures during buildup, hot carrier gas extraction is employed. Experiments are conducted using both a three-jet and a coaxial nozzle to assess the influence of nozzle geometry. Additionally, the experiments are conducted within a shielding gas chamber to demonstrate the benefits of such a chamber in mitigating oxidation. Finally, the study reveals that by appropriately combining the parameters of carrier gas volume flow, shield gas volume, and travel speed, it is possible to fabricate titanium components, which fulfill the requirements regarding oxygen content of aerospace and medical applications even without the utilization of a shielding gas chamber.

Localized defect frequencies for Laser Metal Deposition processes

Laser Metal Deposition (LMD) uses laser energy and powder material to create structures on existing components. It is capable of producing cost-effective multi-material compositions, such as reinforcing metals with ceramic particles for improved wear resistance. However, the use of dissimilar materials often leads to defects, particularly delamination. Previous studies have found a connection between these defects and specific airborne acoustic emissions (AE).To mitigate the impact of defects, extensive optimization of process parameters and real-time process monitoring are recommended. For AE, precise localization of defects is crucial besides to time- and frequency-resolved information, especially while producing multiple components on a substrate material.This study evaluates multi-sensor arrays for the localization of delamination defects. The research investigates the influence of localization algorithms and array patterns on the accuracy and reliability of defect localization. Experiments were conducted on a test platform with simulated acoustical events to determine the most suitable localization setup.

Off-axis optical system for the monitoring of the Laser Metal Deposition process

The Laser Metal Deposition (LMD) is emerging among the additive manufacturing (AM) technologies of metals for its versatility. It takes advantage of the flexibility of a laser source and a powder flow to fabricate or repair components with very complex features. The challenging process conditions that characterize the processing of metallic materials (temperatures and stresses) underlie the occurrence of several defects that plague such AM processes. Thus, the necessity to develop monitoring systems that can comprehensively analyze the production phase arises. In the present work, an innovative off-axis optical system consisting of three cameras with appropriate filters is proposed for the monitoring of LMD process. The peculiarity of this system lies in the capability of monitoring the spatial evolution of the melt pool, enabling eventually a complete control of the deposition process. In fact, through the use of properly developed image processing algorithms, the system enables the tridimensional definition of the size and shape of the melt pool and at the same time the reconstruction of each deposited layer. The potential of the monitoring system was tested on a series of thin-walled components. Subsequently, the analysis results were validated by comparison with 3D scanning of the parts and analyses performed using a coaxial monitoring system.

Effect of laser direct metal deposition process on the microstructure and mechanical properties and temperature and stress fields of 24CrNiMo

Effect of laser direct metal deposition process on the microstructure and mechanical properties and temperature and stress fields of 24CrNiMo

Off-axis monitoring of the melt pool spatial information in Laser Metal Deposition process

Laser Metal Deposition (LMD) is one of the most promising Additive Manufacturing (AM) technologies for the fabrication, coating and repair of metal components. Although, due to the high number of factors influencing the process, defects may arise, as geometrical and dimensional inaccuracies, high residual stresses and internal voids, with effects on the quality and the mechanical performances of the produced parts. Thus, the need for in-process monitoring systems capable of timely detecting the onset of defects and process anomalies emerged.In this work, an in-process monitoring system suitable for LMD was presented. It consisted of an industrial CMOS camera placed in the LMD machine chamber and set for the acquisition of images showing the melt pool area. Through the use of properly developed image processing algorithms, the monitoring system was capable to extract in-process the melt pool 2D spatial coordinates and to depict the geometry of the fabricated samples. Moreover, specific indexes related to the deposited height were computed in order to evaluate the quality of the process/product. The potentiality of such monitoring method lies in the simplicity of the equipment, and, mostly, in the possibility of monitoring the spatial evolution of the melt pool without interrupting the process and enabling, eventually, a further control of the LMD process. The monitoring system was tested on two 316L thin-walled components and results were validated by comparing the data obtained from the monitoring with a consolidated post-process 3D scanning method.

Initial experiments to regenerate the surface of plasma-facing components by wire-based laser metal deposition

Plasma-facing components (PFC) in nuclear fusion reactors are exposed to demanding conditions during operation. The combination of thermal loads, plasma exposure as well as neutron induced damage and activation limits the number of materials suitable for this application. Due to its properties, tungsten (W) is foreseen as plasma-facing material (PFM) for the future DEMOnstration power plant. It is considered suitable due to its exceptionally high melting point, excellent thermal conductivity, low tritium retention and low erosion resistance during plasma exposure. But even tungsten armored PFCs have a limited lifetime due to, among other factors, surface erosion and the resulting thickness reduction of the armor material.In-situ local deposition of tungsten by means of additive manufacturing (AM) could counteract surface erosion and thus increase the service life span of PFCs. After evaluation of the potential AM processes qualified for this task, the wire-based laser metal deposition (LMD-w) process was selected as the most suitable process. First trials were conducted to examine if it is possible to reliably deposit tungsten onto tungsten substrate using the LMD-w process. In these first studies, single welding beads were generated, and in later experiments, entire layers were created from several welding beads which are arranged next to each other. To ensure reproducibility of the results, the substrate temperature was kept constant. Further experiments aimed at the elimination or minimization of problems such as oxidation, occurrence of balling defects, porosity, cracking, surface waviness and insufficient connection to the substrate. To increase the welding bead quality, the input parameters like laser power, deposition velocity, wire feed rate, inert gas flow, as well as the wire position were optimized. Furthermore, stacking of several layers, as well as the remelting of an already created layer, were carried out and investigated. This study represents the first steps in testing the feasibility of an in-situ surface regeneration concept for PFCs.

(Invited) Overview of Ionic Liquid Electrolytes Doped with δ-Metal Halides for Advanced Post-Lithium-Ion Batteries

Humankind is currently facing a global transition towards a green electrification of both energy production and transportation. There is an urgent need to find new approaches for the storage of energy derived from renewable sources, such as solar irradiation, wind and waves. In addition, electric cars require energy storage or conversion systems capable of providing engine power. To these ends, secondary batteries are an attractive and viable solution, especially in the form of the relatively mature Li-ion technology. Unfortunately, Li power sources suffer from high cost, low Li earth-crust abundance, and toxicity of their electrochemical components (e.g., the Co-based cathodes). Such disadvantages demand the exploration of new energy storage devices based on alternative chemistries (e.g., Na, Mg, Ca).Since their discovery [1-5], electrolytes based on disordered or delta metal halide salts (e.g., δ-MgCl2, δ-LiCl, δ-MgI2) have received widespread attention due to their intriguing physical-chemical properties. Subsequently, electrolytes comprised of ionic liquid solvents dispersing various δ-metal halide salts were investigated [6-9]. These latter ion-conducting systems are characterized by: (i) very high room-temperature ionic conductivity; (ii) wide thermal, chemical and electrochemical stability; and (iii) high coulombic efficiency and very low overpotentials in the metal deposition and stripping processes.In this contribution, a comparison of different families of ionic liquids will be proposed. In particular, the effects of the use of δ-metal halide salts (e.g., δ-MgCl2, δ-LiCl, and δ-NaCl) on the thermal stability, vibrational features, and electrochemical properties of the resulting electrolytes will be considered. The conductivity mechanisms will be analyzed side-by-side, revealing how ionic conductivity is modulated by the metal ions (e.g., Mg2+, Li+, Na+), on the basis of broadband electrical spectroscopy results. Acknowledgments The authors acknowledge support in the form of the following grants: project “Interplay between structure, properties, relaxations and conductivity mechanism in new electrolytes for secondary Magnesium batteries” (Grant Agreement W911NF-21-1-0347-(78622-CH-INT)) of the U.S. Army Research Office; project “ACHILLES” (prot. BIRD219831) of the University of Padua; project “VIDICAT” (Grant Agreement 829145) of the FET-Open call of Horizon 2020; project “Polymer electrolytes for Sodium Batteries” (Grant Agreement 72957-00 01) sponsored by Natrion Inc. and the CUNY Sensor CAT.

Comparison of electrochemical lithium and sodium metal deposition: A surface plasmon resonance spectroscopy investigation

Electrochemical deposition of alkali metals on the electrode surface is important for the development of metal-based batteries with high-energy density. Here, we investigate using electrochemical surface plasmon resonance spectroscopy (EC-SPR) to compare the deposition mechanisms of lithium and sodium metal. The SPR spectrum of the Cu film electrode was clearly observed for both LiPF6 and NaPF6 based organic electrolytes. The corresponding SPR spectra for both Li and Na system were dramatically red-shifted at 1st metal deposition process, indicated direct metal deposition on Cu surface. The Li system repeatedly showed similar red shift until at least the 2nd cycle, while similar red shift was not observed at all in the Na system. This indicated that direct Na-metal deposition on the Cu electrode surface was prevented by some passivation film, formed at 1st deposition process. The complex nature of Na-metal deposition, including the surface film phenomena, is responsible for the instability at the interface between the negative electrode and electrolyte in a Na-based battery system. This suggests that Na-based systems need to be more carefully designed and managed than Li-based systems.

Development of Microfluidic Paper-Based Analytical Devices (µPADs) for Determination of Cd2+, Pb2+, and Cu2+ Ions in Mineral Water

Microfluidic paper-based analytical devices (µPADs) have been successfully developed using dual detection: electrochemical and colorimetric systems. The µPADs have the potential to be used as Pb(II), Cd(II), and Cu(II) sensors to test the quality of water. The fabrication process uses hot embossing and screen-printing methods. The working electrode in the electrochemical zone was enhanced by the bismuth metal deposition process, while in the colorimetric zone, the gold nanoparticles modified with thioctic acid and dansylhydrazine (TA-Au-DNS) were used as a colorimetric sensor to detect Cu. The basic material of µPADs was characterized using a Fourier-transform infrared (FTIR) and a contact angle meter (CAM). In the electrochemical zone, the signals of square wave anodic stripping voltammetry (SWASV) resulted in good detection of Pb(II) and Cd(II) (from 0 to 100 ppb) with a limit of detection of 1.588 and 1.42 ppb, respectively. In the colorimetric zone, the performance of TA-Au-DNS for detecting Cu metal was obtained from readings through the red-green-blue (RGB) sensor as a miniature of µPADs reader. The LOD, LOQ, and average Vx0 (linearity values) in the detection of Cu(II) (from 58 to 100 ppb) are 8.51 ppb, 28.36 ppb, and 0.41%, respectively.