Metal Deposition Process Research Articles

(Invited) Electrochemical Microcalorimetry, a Thermodynamic Approach to Metal Deposition Processes

Electrochemical microcalorimetry measures the heat, which is evolved during an electrochemical process. With our experimental setup tiny electrochemical conversions down to a few percent of a monolayer are sufficient for the determination of the heat, which is evolved at a single electrode. This allows to stay close to equilibrium conditions and thus to determine the reversible contribution to the heat, which is directly proportional to the entropy changes during the electrochemical reaction, including all side reactions like codeposition processes, polarization of the double layer etc.. In this contribution we will present examples, how from the knowledge of the reaction entropy conclusions can be drawn i) on the solvation of Na ions for Na deposition from a diglyme electrolyte, ii) on the reactions steps for the reduction of Ag from Ag-cyanide complexes and iii) the deposition process of Cu2+ from aqueous solutions. We also will present first results of our attempts to measure the reaction volume of Cu bulk deposition and Cu UPD on Au(111) by pressure dependent potential measurements.

Effect of MoO3 buffer layer on the electronic structure of Al–BP interface

The interfacial modification effect of the molybdenum trioxide (MoO3) buffer layer inserted between Al and black phosphorus (BP) was investigated with photoemission spectroscopy. The results show that MoO3 buffer layer can effectively prevent the destruction of the outermost BP lattice by Al thermal deposition and change the interface electronic structure between Al and BP. At the MoO3/BP interface, there is an interface dipole pointing from MoO3 to BP. During the metal deposition process, an interfacial chemical reaction between Al and MoO3 was found. These observations would provide insight for fabricating high-performance BP-based devices.

Magnetic Nitrogen–Doped biochar for adsorptive and oxidative removal of antibiotics in aqueous solutions

Pollution by antibiotics has received attention worldwide because they are difficult to remove in wastewater. Extensive researches on antibiotics removal using adsorption and advanced oxidation processes has not resulted in ideal and effective methods for widespread implementation. Herein, nickel–containing and nitrogen–doped biochars (Ni@NBCs) are synthesized via polymer–assisted metal deposition and pyrolysis processes. These Ni@NBCs exhibit good adsorption capacities and act as catalysts to activate potassium persulfate (PPS) for producing reactive oxygen species, which react with the broad–spectrum antibiotic sulfachloropyridazine (SCP) in an oxidative degradation process. Experimental results of SCP adsorption confirm that the adsorption process follows pseudo–second–order kinetics and Langmuir isotherm models. Oxidative degradation results show that the constructed heterogeneous Ni@NBC/PPS system has excellent SCP degradation ability with degradation rates exceeding 90% within 40 min under certain conditions. The Ni@NBC also exhibits excellent reusability and durability (>75% degradation rate after 20 cycles). The catalytic mechanism and possible degradation pathways for SCP removal are proposed. Considering the adsorption and catalytic properties of Ni@NBCs, such materials show great application prospects for antibiotics removal in water environments.

A Multi-Layered Borophene-Silica-Silver Based Refractive Index Sensor for Biosensing Applications Operated at the Infrared Frequency Spectrum

We have presented the borophene based refractive index sensor for the infrared frequency spectrum of 188 to 250 THz (1.2–1.6 µm) range. The proposed structure was formed by using the Silver-borophene-silica-Ag layered structure. The behaviour of the different analyte (with a different refractive index) material is numerically calculated by placing it on the top of the structure. The behaviour of the structure is identified in terms of absorption, reflectance, physical parameter variation, and oblique angle incident conditions. The presented results provide the basic idea of selecting optimized structure dimensions to get the specific resonating response. This sensor offers the Figure of Merit (FOM) of 444 RIU−1 with high sensitivity of 660 THz/RIU (4471 nm/RIU). The refractive index sensor also provides wide-angle stability for (0° to 80°) for the wide frequency range (239 to 245 THz and 207 to 209 THz). This sensor is developed on the silver metal layer (not required to separate borophene from its origin metal deposition process) and easily fabricated using standard boron fabrication and layered deposition techniques. The results of the proposed structure make it possible to design a basic biosensor structure. This device is also applicable for various THz and biomedical applications.

Covariance matrix adapted grey wolf optimizer tuned eXtreme gradient boost for bi-directional modelling of direct metal deposition process

The process of direct metal deposition for cladding has become extremely popular. Online condition monitoring of the process is necessary to obtain a desired clad geometry. The aforementioned fact has necessitated the development of accurate predictive models for establishing relationships between the input and the output parameters of the process in a bi-directional fashion. The present study attempts to build both forward and backward models of a direct deposition process of austenitic steel utilizing the extreme gradient boost technique. Inspired by the successful application of grey wolf optimization algorithm in solving real life problems, the authors further propose a novel modification of the same and use it to tune the parameters of the model with an aim to improve its performance. The improvement has been accomplished by changing the initial perspective prey location guided by the covariance matrix adaptation and recombination. The new optimization algorithm has been tested and compared with the original algorithm along with some of its variants and several other state-of-the-art meta-heuristics on 23 benchmark objective functions from literature and 5 from CEC 2017. The new optimizer has been further validated on some real engineering case studies. The developed hybrid models for bi-directional mappings using different optimizer turn-by-turn have been trained and tested using statistically augmented experimental data-set. The overall mean absolute percentage errors in testing forward mapping and backward mapping using the model with new optimizer have been found within 10%, which is quite satisfactory. The adequacy of the developed models has also been found acceptable.

Study of magnetoelectrodeposition of lanthanum (III) chloride heptahydrate leached with sulfuric acid

Abstract A rare-earth element (REE) is one of the minerals with many resources in Indonesia and lanthanum is one of REE. Lanthanum is widely used as a material for x-ray screens, glass lenses, optical fiber, capacitor batteries, and ceramics. Electrodeposition is a metal deposition process. The advantages of electrodeposition are easy and inexpensive. The method is simple since it can be done at room temperature, and it is inexpensive because it only requires basic equipment. However, there is a drawback to conventional electrodeposition: the roughness of the resultant layer (non-uniform crystal growth). Magnetoelectrodeposition (MED) is a solution for solving this problem. We employed the MED method in this study, which is the electrodeposition procedure under the influence of a magnetic field, and there has been no previous research on lanthanum MED. The electrode area, magnetic field strength, electroactive concentration, diffusion coefficient, and kinematic electrolyte viscosity were variables used in this study. The lanthanum MED in this study used 98% lanthanum (III) chloride heptahydrate (LaCl3.7H2O) for analysis from Merck, which was leached at a particular concentration of sulfuric acid (H2SO4), using platinum electrodes in three electrochemical cells, and varying the magnetic field strength from 0 to 0.08 Tesla. The results showed that the stronger the magnetic field, the greater the limiting current for lanthanum electrodeposition. The effect of electrode area and electroactive concentration also gives rise to the limiting current. Meanwhile, the viscosity of the solution and the diffusion coefficient will cause a reduction in limiting the current value.

Investigation of deposition welding in vertical and horizontal position with a coaxial laser wire welding head

Deposition welding of components using the laser metal deposition (LMD) process is a proven method of creating 3D structures. It is used for the manufacturing of components, the repair of machine parts and for cladding. Up to now, claddings have mainly been investigated in the flat welding position. Some investigations on deposition welding in vertical orientation are available with different processes. For the cladding of large components, welding in the vertical direction offers advantages. So far, there are no investigations on the LMD process with coaxial wire feeding when welding in vertical direction. Therefore, in this study, the influence of the welding direction, i.e., vertical down and vertical up weld seams, and the influence of the welding speed are investigated. Single weld seams, claddings and a wall are welded. A stable welding process could be achieved for a welding speed parameter window of 100 to 1000 mm/min. The results show that there is a statistical correlation between the welding direction and the waviness of the weld seams. Vertical up weld seams have a lower waviness. Another influence on the waviness is the welding speed. As the welding speed decreases, the waviness increases. The weld seam geometry is strongly dependent on the welding direction. With vertical down weld seams, the width and height of the weld seam vary depending on the distance welded. This can be attributed to the influence of the gravitational force. Vertical up weld seams, on the other hand, have a more uniform shape.

Power and energy capacity tradeoffs in an all-aqueous copper thermally regenerative ammonia battery

Thermally regenerative ammonia batteries (TRABs) can provide energy storage and produce electrical power from low-grade waste heat instead of electricity. The use of all-aqueous copper-based electrolytes has recently produced higher power densities than those achieved using previous TRAB approaches based on reversible metal deposition and dissolution processes, but further gains are possible in power and energy density. We investigated the limitations of power and energy density and how they are impacted by the electrolyte composition and discharge currents. By increasing the ammonia concentration from 1 to 5 M, the power density of the battery increased from 11.2 to 28.5 mW cm−2, but the energy density decreased from 0.56 to 0.31 Wh L−1. Increasing discharge current densities from 4 to 12.5 mA cm−2 increased the average power density during discharge from 2.4 to 5.9 mW cm−2 without appreciable losses in energy density. Increasing the copper concentration from 0.1 to 0.5 M increased both energy density to 2.15 Wh L−1 and energy efficiency to 2.2% but did not substantially impact the power density. These results represent the highest performance metrics achieved for a low-grade waste heat to electricity system.

Effect of Ultrasonic Nanocrystal Surface Modification Treatment at Room and High Temperatures on the High-Frequency Fatigue Behavior of Inconel 718 Fabricated by Laser Metal Deposition

In this work, the effect of ultrasonic nanocrystal surface modification (UNSM) treatment at room and high temperatures (RT and HT) on the high-frequency fatigue behavior of Inconel 718 alloy fabricated by laser metal deposition (LMD) process was experimentally investigated. UNSM treatment at RT and HT modified a surface morphology and produced a nanostructured surface layer with a thickness of approximately 120 and 140 µm, respectively. The surface roughness of the untreated sample was reduced, while the surface hardness was notably increased after the UNSM treatment at RT and HT. Both increased with increasing the UNSM treatment temperature. Fatigue behavior of the untreated samples at various stress levels was slightly improved after the UNSM treatment at RT and HT. This is mainly due to the formation of a fine grained nanostructured surface layer with reduced porosity and highly induced compressive residual stress. Fatigue mechanisms of the samples were comprehensively discussed based on the quantitative SEM fractographic analysis.

Inline Optical Coherence Tomography for Multidirectional Process Monitoring in a Coaxial LMD-w Process

Within additive manufacturing, process stability is still an unsolved challenge. Process instabilities result from the complexity of laser deposition processes and the dependence of the quality of the workpiece on a variety of factors in the process. Because a stable process is dependent on many different factors, permanent precise inline monitoring is required. The suitability of the optical coherence tomography (OCT) measuring system integrated into a wire-based laser metal deposition (LMD-w) process for the task of process control results from its high resolution and high measuring speed, and from coaxial integration into the laser process, which allows for a spatially and temporally resolved representation of the weld bead topography during the process. To realize this, a spectral domain OCT (SD-OCT) system was developed and integrated into the beam path of the process laser. With the aid of suitable optics, circular scanning was realized, which allows for the 3D depth information to be displayed independently of the direction of movement of the processing head and the centrally running wire. OCT makes it possible to detect the process-typical topography deviations caused by process variations and thus paves the way for adaptive process control that could make additive laser processes more reproducible and precise in the future.

A coupled multiphase Lagrangian-Eulerian fluid-dynamics framework for numerical simulation of Laser Metal Deposition process

We present a Computational Fluid Dynamics (CFD) framework for the numerical simulation of the Laser Metal Deposition (LMD) process in 3D printing. Such a framework, comprehensive of both numerical formulations and solvers, aims at providing a sufficiently exhaustive scenario of the process, where the carrier gas, modeled as an Eulerian incompressible fluid, transports metal powders, tracked as Lagrangian discrete particles, within the 3D printing chamber. On the basis of heat sources coming from the laser beam and the heated substrate, the particle model is developed to interact with the carrier gas also by heat transfer and to evolve in a melted phase according to a growth law of the particle liquid mass fraction. Enhanced numerical solvers, characterized by a modified Newton-Raphson scheme and a parallel algorithm for tracking particles, are employed to obtain both efficiency and accuracy of the numerical strategy. In the perspective of investigating optimal design of the whole LMD process, we propose a sensitivity analysis specifically addressed to assess the influence of inflow rates, laser beams intensity, and nozzle channel geometry. Such a numerical campaign is performed with an in-house C++ code developed with the deal.II open source Finite Element library, and publicly available online.

Influence of γ/γ′ morphology evolution on the mechanical properties of Ni-based single crystal superalloys formed by laser metal deposition

The variation in hardness and tensile properties of Ni-based single crystal (SX) superalloy DD6 during laser metal deposition processing has been investigated, and the effects of laser scanning velocity and post heat-treatment on the evolution of microstructure and its interaction with mechanical properties of deposited region were determined. It is found that the microstructure of as-deposited Ni-based single crystal superalloy mainly consists of columnar dendrite epitaxially growing from the substrate. The fine γ′ phase microstructure and dense γ/γ′ phase interfaces contribute more to the microstructural evolution and mechanical properties of deposited part formed by laser metal deposition. Furthermore, the heat treatment reduces the mechanical properties of deposited sample due to the introducing of stray grains that destroys the original single crystallinity. The mechanism unraveled here could shed light on the reliability evaluation and parameter selection of the laser metal deposition technique and other directed energy deposition technology.

Heat Treatment Design for IN718 by Laser Metal Deposition with High Deposition Rates: Modeling, Simulation, and Experiments.

Laser metal deposited processed Ni-based superalloy IN718 is characterized by elemental micro-segregation, anisotropy, and Laves phases due to the rapid solidification and therefore needs homogenization heat treatment to achieve comparable properties of wrought alloys. In this article, we report a simulation-based methodology to design heat treatment IN718 in a laser metal deposition (LMD) process by using Thermo-calc. Initially, the finite element modeling simulates the laser melt pool to compute the solidification rate (G) and temperature gradient (R). Then, the primary dendrite arm spacing (PDAS) is computed through Kurz-Fisher and Trivedi modeling integrated with finite element method (FEM) solver. Later, a DICTRA homogenization model based on the PDAS input values computes the homogenization heat treatment time and temperature. The simulated time scales are verified for two different experiments with contrast laser parameters and are found to be in good agreement confirmed with the results from scanning electron microscopy. Finally, a methodology for integrating the process parameter with the heat treatment design is developed, and a heat treatment map for IN718 is generated that can be integrated with an FEM solver for the first time in the LMD process.

Metal additive manufacturing repair study on rail steel with Stellite 6 powder

Metal Additive Manufacturing repair study on rail steel with Stellite 6 powder is reported in this study. Laser Metal Deposition (LMD) process using Stellite 6 powder deposited on rail steel substrate was investigated for microhardness, wear and shear test properties. Microstructural analysis and microhardness measurements on cross-sectioned samples extracted from Stellite 6 clad on rail steel specimens show positive results. Wear testing was conducted using laboratory ball-on-disc tribometer tests on rail steel and Stellite 6 cladded disc specimens. The measured wear data and wear coefficients for Stellite 6 and rail steel were fitted to Archard’s wear model. Shear testing was conducted to measure the clad/substrate shear strength as an indication of the metallurgical bond strength. The experimental study results demonstrate the potential use of metal additive repair method for rail steel applications. Development of a novel Portable Laser Metal Deposition System (PLMDS) will be presented as a potential metal additive manufacturing repair tool for on-site metal repair applications in the future.

Modulation of electrical properties in MoTe2 by XeF2-mediated surface oxidation.

Transition metal dichalcogenides (TMDs) are promising candidates for the semiconductor industry owing to their superior electrical properties. Their surface oxidation is of interest because their electrical properties can be easily modulated by an oxidized layer on top of them. Here, we demonstrate the XeF2-mediated surface oxidation of 2H-MoTe2 (alpha phase MoTe2). MoTe2 exposed to XeF2 gas forms a thin and uniform oxidized layer (∼2.5 nm-thick MoOx) on MoTe2 regardless of the exposure time (within ∼120 s) due to the passivation effect and simultaneous etching. We used the oxidized layer for contacts between the metal and MoTe2, which help reduce the contact resistance by overcoming the Fermi level pinning effect by the direct metal deposition process. The MoTe2 field-effect transistors (FETs) with a MoOx interlayer exhibited two orders of magnitude higher field-effect hole mobility of 6.31 cm2 V−1 s−1 with a high on/off current ratio of ∼105 than that of the MoTe2 device with conventional metal contacts (0.07 cm2 V−1 s−1). Our work shows a straightforward and effective method for forming a thin oxide layer for MoTe2 devices, applicable for 2D electronics.

Effect of DED process parameters on distortion and residual stress state of additively manufactured Ti-6Al-4V components during machining

One of the major challenges in high-deposition rate Directed Energy Deposition processes is the resultant residual stresses generated during material deposition, often leading to distortion and poor material characteristics. Important part families suitable for DED process in aerospace sector are thin-wall components, characterized by a large base surface area with rib-like strengthening structures. Here, the substrate plate can be designed to be a part of the final component. The integration of substrate plate into final component results in possible deformation due to residual stress release during machining. This paper therefore investigates the effect of various powder-based Laser Metal Deposition process parameters and strategies on the residual stress state of the additively manufactured Ti-6Al-4V components and the resulting stress release during machining process. The analysis has been carried out during the machining process by including in-process strain measurements of the substrate. The embraced layer removal method allows the determination of machining zone specific stress release mapping, based on an analytical and FEM-model. Hence, the initial residual stress state of the builds was calculated, which revealed that although the heat treatment resolved most of the residual stresses, also in heat treated parts residues were identified depending on the part clamping during the treatment. Furthermore, the study revealed that the significant residual stresses are present in the layers close to the substrate.

A Digital Twin Approach for the Prediction of the Geometry of Single Tracks Produced by Laser Metal Deposition

Flexible manufacturing processes such as laser metal deposition exhibit high potential for a production solely defined by software to cope with the current challenges of production systems. The determination of suitable machine parameters for the production of novel materials and geometries however requires extensive experimental effort. Existing simulative approaches do not offer sufficient accuracy to predict the relevant machine parameters in a satisfactory way. This paper presents a new concept, in which we apply a digital twin to provide a step towards a fully software-defined and predictable laser metal deposition process. The presented concept includes relevant data of the machines as well as data-driven machine learning models and physics-based simulation models. This enables a more reliable prediction of geometries of single tracks which was validated on a laser metal deposition machine.

The effect of pre- and post-heat treatment on hardness and residual stress by laser metal deposition process of tungsten carbide (MetcoClad 52052) cladding on a CK45 substrate

During laser metal deposition (LMD), large temperature gradient occurs due to the process. These fast changing of temperature leads to high residual stresses, which in turn causes the formation of cracks and deformation. These residual stresses can be reduced with the heat treatments. In this way, the quality of the deposition can be extremely improved. This investigation shows the results of the pre and post heat treatment in terms of hardness and residual stresses in LMD process of mix powder tungsten carbide (MetcoClad 52052) cladding on a CK45 substrate . An improvement of the quality of deposition and surface integrity can be observed.

Automated platform for consistent part realization with regenerative hybrid additive manufacturing workflow

Nowadays, the role of hybridization within the wider manufacturing ecosystem gains significant momentum with multiple commercial solutions already available on the market. Despite the very promising benefits of combining and selectively exploiting the advantages of additive and subtractive technologies on the same machine, hybrid additive manufacturing is far from reaching its full potential. One of the central limitations of existing hybrid process chains is the lack of a harmonized, structured and automated workflows to support an adaptive manufacturing strategy. This work is motivated by the need to bridge this gap and to capture the logic behind an adaptive hybrid process chain with the aim to support the achievement of enhanced product quality and improved operational efficiency in hybrid additive manufacturing. The paper discusses the implementation of a hybrid CAx platform and the underlying methodology aiming at the dynamic reduction of variabilities associated with the laser metal deposition process. The hybrid workflow identifies the most adapted sequence and planning of additive and subtractive operations while considering part inspection as an in-envelope functionality to quantify the geometrical and dimensional part deviations and to trigger the regenerative mechanism. The methodology is demonstrated on a hybrid machine by deploying laser ablation for the in situ removal of build deviations and an adapted deposition operation as part of a regenerative strategy leading to higher part confidence.

New nanocomposites for deep water deoxygenation

New metal-polymer nanocomposites for deep water deoxygenation have been obtained and studied. A macro- and monoporous sulphocation exchanger with a nanometer pore size was used as the polymer matrix, and the metal was nanodispersed copper deposited in the pores of the matrix. A specific feature of the studied nanocomposites is their sodium ionic form, which eliminates the possibility of the formation of soluble copper oxidation products. The established linear dependence of the copper capacity on the number of cycles of ion-exchange saturation - chemical deposition shows that the process of metal deposition into the pores of the matrix does not have significant obstacles during 10 cycles and contributes to the production of high-capacity samples.The high efficiency and duration of the life cycle of high-capacity copper ion exchanger nanocomposites have been shown. Experimental studies of water deoxygenation in column-type apparatus with a nanocomposite nozzle were confirmed by a theoretical analysis of the process dynamics. Experimental data and theoretical calculations showed the deep level of water deoxygenation had practically unchanged values of pH and electrical conductivity. Residual oxygen can be controlled and does not exceed 3 μg/l (ppb).The hygienic and economic substantiation of the expediency of using the obtained nanocomposites is provided. The necessity of using modern nanocomposite metal-polymer materials for deep water deoxygenation circulating in technological systems was analysed. When using this innovation, the metal components of the distribution facilities will be protected from corrosion and, therefore, the hygienic requirements for the water quality of centralised drinking water supply systems will be ensured. Deep chemical water deoxygenation using copper ion-exchange polymer nanocomposites in sodium formallows solving the problem of the corrosion resistance of metals, ensuring that water meets hygienic requirements on a large scale.The competitive advantage of the considered water deoxygenation system in comparison with the known systems is the rejection of the use of precious metals-catalysts (palladium, platinum), pure hydrogen, and complex design solutions. The proposed new nanocomposite installation for water deoxygenation is characterised by its ease of use and can be built into a filter system for water purification.SWOT analysis of the advantages and disadvantages of the proposed method of water deoxygenation showed that its main advantages are the high oxygen capacity of the nanocomposite, low residual oxygen content (3 ppb (μg/l)) in the water, and ease of operation of the deoxygenator. Calculations of the economic efficiency of the nanocomposite have been carried out. The breakeven point is reached when producing only ~100 l of nanocomposite and a volume of sales ~1,600,000 roubles, above which a profit can be obtained. The payback period for an investment of ~15,000,000 roubles is rather short and will not exceed 2 years.