Metal Deposition Research Articles

Influences of friction stir processing on the microstructure and properties of TC4 titanium alloy by laser metal deposition

To enhance the properties of TC4 titanium alloy samples prepared by Laser Metal Deposition (LMD), while minimizing metallurgical defects and increasing relative density of the samples, the advanced Friction Stir Processing (FSP) technology was employed to conduct a refined secondary modification on the LMD-deposited TC4 titanium alloy samples. The comprehensive influences of FSP on the microstructure and properties of the as-deposited TC4 titanium alloy were emphatically investigated. The results reveal that the as-deposited TC4 titanium alloy exhibits a microstructure characterized primarily by columnar grains interspersed with a minor amount of equiaxed grains in the vertical section. After FSP treatment, the microstructure transforms into a new morphology where more refined equiaxed grains coexist with bimodal structures. Meanwhile, on the horizontal plane, the existing equiaxed grains are further refined, and the microstructure gradually transitions from the original Widmanstätten and basketweave structures to a more uniform laminar structure. Accordingly, the transformation of the microstructure leads to enhanced mechanical properties of the TC4 titanium alloy. Compared to the untreated as-deposited titanium alloy, the hardness of the FSP-processed samples significantly increases by 46.9 HV1 on the horizontal plane and 33.8 HV1 on the vertical plane. Additionally, the reduction in friction coefficient (from 0.47 to 0.41), a substantial decrease in wear mass (3.7 mg), and a slight improvement in the corrosion resistance of the titanium alloy collectively demonstrate the effectiveness of the FSP process in enhancing the performance of as-deposited TC4 titanium alloy.

Laser Metal Deposition of Rene 80—Microstructure and Solidification Behavior Modelling

New developments in nickel-based superalloys and production methods, such as the use of additive manufacturing (AM), can result in innovative designs for turbines. It is crucial to understand how the material behaves during the AM process to advance the industrial use of these techniques. An analytical model based on reaction–diffusion formalism is developed to better explain the solidification behavior of the material during laser metal deposition (LMD). The well-known Scheil–Gulliver theory has some drawbacks, such as the assumption of equilibrium at the solid–liquid interface, which is addressed by this method. The solidified fractions under the Scheil model and the pure equilibrium model are calculated using CALPHAD simulations. A differential scanning calorimeter is used to measure the heat flow during the solid–liquid phase transformation, the result of which is further converted to solidified fractions. The analytical model is compared with all the other models for validation.

Nanoscale Surface Metal-Coating Method without Pretreatment for High-Magnification Biological Observation and Applications.

Biospecimen imaging is essential across various fields. In particular, a considerable amount of research has focused on developing pretreatment techniques, ranging from freeze-drying to the use of highly conductive polymers, and on advancements in instrumentation, such as cryogenic electron microscopy. These specialized techniques and equipment have facilitated nanoscale and microscale bioimaging. However, user access to these environments remains limited. This study introduced a novel technique to achieve high conductivity in bioimaging by employing a magnetically controlled sputtering cathode to facilitate low-temperature deposition and low-electron bombardment. This approach allows for the convenient high-magnification observation of highly structured three-dimensional specimens, such as pill bugs and butterfly wings, and fragile specimens, such as single-cell protozoan parasites, using metal deposition only. Furthermore, it is easily accessible in the field of bioimaging because it does not require any pretreatment and enables surface analysis of biospecimens with an electron microscope using only a single pretreatment process. Protozoa, which are microorganisms, were successfully observed at high magnification without structural changes due to thermal denaturation. Furthermore, metallic film deposition and electrochemical signal measurements using these metallic films were achieved in pill bugs.

Screening Ammonium-Based Cationic Additives to Regulate Interfacial Chemistry for Aqueous Ultra-Stable Zn Metal Anode.

The interfacial dynamics and chemistry at the electrolyte/metal interface, particularly the formation of an adsorption interphase, is paramount in dictating the reversibility of Zn metal deposition and dissolution processes in battery systems. Herein, a series of different cationic ammonium-based electrolyte additives are screened that effectively modulate the interfacial chemistry of zinc anodes in aqueous electrolytes, significantly improving the reversibility of Zn metal plating/stripping processes. As initially comprehensive investigation by combining theoretical calculation and molecular dynamic simulation, the tetramethylammonium cation, with its specific molecular structure and charge distribution, is identified as pivotal in mediating the Zn(H2O)6 2+ solvation shell structure at the electrode/electrolyte interface and shows the strong resistance against electrolyte corrosion as revealed by X-ray and optical measurements. As a result, the Zn||Zn symmetric cell with optimal electrolyte lasts for over 4400 h of stable plating/stripping behaviors, and the Zn||Cu asymmetric cell stabilizes for 2100 cycles with an average Coulombic efficiency of 99.8%, which is much better than the-state-of-art progress. Consequently, full-cells coupled with various cathodes showcase improved electrochemical performance, displaying high capacity-retention and low self-discharge behaviors. These findings offer essential insights of cationic additives in ameliorating zinc anode performance.

Studies on the content of toxic metals in teeth: A narrative review of literature.

The presence of toxic metals in the human environment can have detrimental effects on people's wellbeing. This literature review examines the ways in which various environmental and non-environmental factors can contribute to the accumulation of heavy metals in hard dental tissues. It is of the utmost importance to ensure the safety of the environment by restricting the presence of toxic metals originating from both industrial and non-industrial sources. The aim of this study is to analyze current research and identify the primary sources of heavy metal exposure and the mechanisms by which these metals are deposited in dental tissues. Moreover, the objective of this review is to synthesize data from various studies to determine the main environmental and non-environmental sources of toxic metal exposure that contribute to their presence in dental tissues, as well as the biological and chemical processes that are responsible for the deposition of heavy metals in hard dental tissues. Additionally, the review aims to assess the impact of heavy metal accumulation on dental health and its potential systemic effects on overall well-being. The accumulation of heavy metals in the teeth is influenced by a number of factors, such as age, systemic conditions, the nutritional status, and dental caries. The presence of supernumerary teeth results in altered levels of microelements, including an increase in cadmium (Cd) and copper (Cu). Additionally, smoking exacerbates toxic metal accumulation, especially Cd and lead (Pb), and disrupts the balance of essential minerals within the teeth. These findings underscore the impact of environmental pollution on dental health and highlight the potential of teeth as biomarkers of environmental exposure, emphasizing the need for continued research to address the health risks associated with environmental toxins.

Geochemical and mineralogical characterization and resource potential of the Namib Pb-Zn tailings (Erongo Region, Namibia)

In Southern Africa, historic mining and mineral processing of base metal deposits have almost exclusively focussed on the extraction of major metals, leading to the loss of remaining valuable raw materials into tailings dumps and waste rock piles. At the Namib Pb-Zn mine (Erongo Region, Namibia), historic base metal tailings deposits are present as unreclaimed exposed waste piles. The tailings comprise silt- (fraction A: d50 = 25 to 48 μm) to sand-sized (fraction B: d50 = 86 to 185 μm; fraction C: d5o = 210 to 230 μm) material and contain major concentrations of base metals (Pb av. 1.15 mass%, Zn av. 3.20 mass%), S (av. 9.95 mass%), as well as lower values of other metals (Cu av. 490 μg/g, Cd av. 133 μg/g, Ag av. 22 μg/g), and critical elements like Sb (av. 14.7 μg/g) and In (14.3 μg/g). Former mineral processing only targeted the extraction of galena and sphalerite. As a consequence, qualitative mineralogical composition of the tailings is similar to that of the primary ore. Ca-Fe-Mg(-Mn) carbonates, quartz, micas, chlorite, minor graphite, magnetite, and rare parisite relate to the former host rock and gangue matrix, whereas Fe-rich sphalerite, galena, magnetite, pyrite with minor pyrrhotite, rare arsenopyrite, marcasite, cassiterite, and accessory scheelite are original constituents of the primary ore. Reprocessing of such a material would be challenging, but a mixed Pb-Zn concentrate enriched in Cd and Ag might be obtained. In future, possible reprocessing of Namib tailings and associated disposal of wastes into an appropriately designed repository would not only generate valuable metal commodities, but such activities would also eliminate a major metal pollution source from the local environment.

Prevention of solidification cracking in alloy 718 additive manufacturing by laser metal deposition method based on control guidelines for weld solidification cracking

The chemical composition of alloy 718 powder was optimized to suppress a solidification cracking in the additive manufactured part by the laser metal deposition method. The relationship between the condition of additive manufacturing and defects was evaluated. A lack of fusion was observed on the low heat input (low energy density), and the solidification cracking occurred on the high heat input (high energy density). The powder composition of alloy 718 was attempted to be optimized from a theoretical approach of the solidification cracking susceptibility. It was found that Si and B had a significant influence on the solidification cracking, therefore a preventive powder with reduced Si and B was developed. The effects of Si and B on solidification cracking were compared by reproducing the solidification conditions during additive manufacturing and evaluating the solidification brittle temperature range (BTR) using the Varestraint test. It was found that the BTR of the preventive material was smaller, and the solidification cracking susceptibility was improved. In addition, the solidification cracking did not occur in additive manufacturing using the preventive powder. In other words, it is suggested that the countermeasure for weld solidification cracking leads to the prevention of solidification cracking in additive manufacturing directly, and the effectiveness of the optimization of powder composition was verified.

Thermal Conductivity of 3D Printed Metal using Extrusion-based Metal Additive Manufacturing Process

Abstract In this study, the thermal conductivity of 3D-printed 316L stainless steel parts using the bound metal deposition (BMD) method, an extrusion-based 3D printing technology, were examined experimentally and validated numerically using finite element analysis (FEA). Various critical printing parameters were examined, including infill density, skin overlap percentage, and print sequence to study their effect on the printed thermal conductivity. A heat conduction experiment was performed on the 3D-printed samples of 316L stainless steel followed by a FEA. The results from this investigation revealed that an increase in 3D printing infill density correlated with a rise in effective thermal conductivity. Conversely, a substantial decrease in thermal conductivity was observed as porosity increased. For instance, at a porosity level of 16.5%, the thermal conductivity experienced a notable 33% reduction compared to the base material. The skin overlap percentage, which governs how much the outer shell of adjacent layers overlaps, was found to impact heat transfer across the overall part surface. A higher overlap percentage was associated with improved thermal conductivity, although it could affect the surface finish of the part. Furthermore, the study explored the print sequence, focusing on whether the outer wall or infill was printed first. Printing the outer wall first resulted in higher thermal conductivity values than that obtained from printing the infill first. Therefore, it is crucial to carefully consider these factors during the BMD 3D printing process to achieve the desired thermal conductivity properties.

A comparative study on corrosion and mechanical properties of laser-cladded X2CrNiMoN22-5-3 duplex stainless steel on 42CrMo4 steel substrate

Duplex stainless steel is an alloy that combines the advantages of austenitic stainless steel and ferritic stainless steel. It has excellent corrosion resistance, high strength, and good weldability. One of the main problems in marine shafts using X2CrNiMoN22-5-3 Duplex Stainless Steel (2205) is bending and warping over time. In this study, 42CrMO4 (MO40) steel was clad with 2205 dual-phase steel using direct metal deposition with wire to simultaneously utilize the mechanical properties, and corrosion resistance. Perform metallographic imaging, corrosion test, and tensile test, to maintain the quality of the cladding. The results show that the corrosion potential of 2205 cladding layer is −0.65 (including semi-passive zone), while the control sample of 2205 had a corrosion potential of −0.26, and the MO40 substrate had a corrosion potential of −0.1 (highlighting the advantage of the cladding in thermodynamics term). EIS results showed that the REISMO40=2325Ω, REIS2205=24315Ω, and REIS2205cladded=216133Ω. The corrosion rate for the substrate, control sample, and laser-clad sample were 0.33, 0.15, and 0.00095 mm/year, respectively, without significant loss in tensile properties. The final strength for MO40(with 2205 clad) reaches 672 MPa with a 14 % decrease from 788 for MO40. In this case, we still have a 36 % increase in strength compared to the 2205 sample. It seems that the bent problem of the pure 2205 marine shaft can be solved completely in this case and continues to be solved in our ongoing work.

Simultaneous Photocatalytic Production of H2 and Acetal from Ethanol with Quantum Efficiency over 73% by Protonated Poly(heptazine imide) under Visible Light.

In this work, protonated poly(heptazine imide) (H-PHI) was obtained by adding acid to the suspension of potassium PHI (K-PHI) in ethanol. It was established that the obtained H-PHI demonstrates very high photocatalytic activity in the reaction of hydrogen formation from ethanol in the presence of Pt nanoparticles under visible light irradiation in comparison with K-PHI. This enhancement can be attributed to improved efficiency of photogenerated charge transfer to the photocatalyst's surface, where redox processes occur. Various factors influencing the system's activity were evaluated. Notably, it was discovered that the conditions of acid introduction into the system can significantly affect the size of Pt (cocatalyst metal) deposition on the H-PHI surface, thereby enhancing the photocatalytic system's stability in producing molecular hydrogen. It was established that the system can operate efficiently in the presence of air without additional components on the photocatalyst surface to block air access. Under optimal conditions, the apparent quantum yield of molecular hydrogen production at 410 nm is around 73%, the highest reported value for carbon nitride materials to date. The addition of acid not only increases the activity of the reduction part of the system but also leads to the formation of a value-added product from ethanol-1,1-diethoxyethane (acetal) with high selectivity.

Comprehensive study on physicochemical properties of materials based on titanium suboxides

This study focuses on the surface structures and microstructural changes of titanium dioxide nanotubes, when electrochemically coated with platinum and/or palladium. Ti samples anodized in a fluorine-containing electrolyte exhibit self-organized nanotubes of varying diameters with open pores. Annealing at 773 K led to compaction of the porous layer, the formation of cracks, and the appearance of corrugation in the nanotubes. The deposition of platinum produced a transition from a nanotubular surface structure to a microcrystalline structure consisting of rutile crystallites. The palladium-coated samples showed fused blocks characteristic of titanium suboxides. The tubular structure was preserved, even after crystallization. SEM images revealed a comb-like pattern in coatings with varying metal content. XRPD analysis confirmed the presence of anatase and elemental titanium. PdO was detected on the surface of the thermally treated samples. For samples co-treated with Pd and Pt, mutual diffusion of the two metals took place during the heat treatment. The findings reveal surface characteristics, metal deposition effects, and phase composition of titania nanotubes, providing valuable insights for further research.

Tailoring the Electrode‐Electrolyte Interface for Reliable Operation of All‐Climate 4.8 V Li||NCM811 Batteries

AbstractCombining high‐voltage nickel‐rich cathodes with lithium metal anodes is among the most promising approaches for achieving high‐energy‐density lithium batteries. However, most current electrolytes fail to simultaneously satisfy the compatibility requirements for the lithium metal anode and the tolerance for the ultra‐high voltage NCM811 cathode. Here, we have designed an ultra‐oxidation‐resistant electrolyte by meticulously adjusting the composition of fluorinated carbonates. Our study reveals that a solid‐electrolyte interphase (SEI) rich in LiF and Li2O is constructed on the lithium anode through the synergistic decomposition of the fluorinated solvents and PF6− anion, facilitating smooth lithium metal deposition. The superior oxidation resistance of our electrolyte enables the Li||NCM811 cell to deliver a capacity retention of 80 % after 300 cycles at an ultrahigh cut–off voltage of 4.8 V. Additionally, a pioneering 4.8 V‐class lithium metal pouch cell with an energy density of 462.2 Wh kg−1 stably cycles for 110 cycles under harsh conditions of high cathode loading (30 mg cm−2), low N/P ratio (1.18), and lean electrolytes (2.3 g Ah−1).

The Effect of Optimized Substrate Orientation on Layer Step in Laser Metal Deposition of Single-Crystal Nickel-Base Superalloys.

Laser metal deposition is a promising way to repair the surface defects of single-crystal components in turbo engines. Understanding the mechanisms and improving the efficiency of the repair have been long-standing problems. In this study, the influence of the substrate orientation on the laser metal deposition (LMD) was investigated and its effect on repair layer-step was examined. LMD experiments were conducted on single crystal superalloys with a normal substrate orientation (001)/[100] and with an optimized substrate orientation (101)/[101¯]. It reveals that the laser cladding with the optimized orientation leads to a larger height of the [001] dendrite region than that with the normal orientation. The calculated results of the growth velocity, thermal gradient, and susceptibility to CET in the dendrite-preferred growth direction indicate that, for the (101)/[101¯] orientation, the [001]/[100] boundary is located at relative high position in each layer, which not only decreases the formation ability of stray grain significantly, but also eliminates the appearance of the maximum susceptibility. This makes the necessary dilution position much higher, and thus, a large cladding step can be selected. Our findings could find potential applications in laser repair of single-crystal components.

Improvement of High Temperature Wear Resistance of Laser-Cladding High-Entropy Alloy Coatings: A Review

As a novel type of metal material emerging in recent years, high-entropy alloy boasts properties such as a simplified microstructure, high strength, high hardness and wear resistance. High-entropy alloys can use laser cladding to produce coatings that exhibit excellent metallurgical bonding with the substrate, thereby significantly improvement of the wear resistance of the material surface. In this paper, the research progress on improving the high-temperature wear resistance of high entropy alloy coatings (LC-HEACs) was mainly analyzed based on the effect of some added alloying elements and the presence of hard ceramic phases. Building on this foundation, the study primarily examines the impact of adding elements such as aluminum, titanium, copper, silicon, and molybdenum, along with hard ceramic particles like TiC, WC, and NbC, on the phase structure of coatings, high-temperature mechanisms, and the synergistic interactions between these elements. Additionally, it explores the potential of promising lubricating particles and introduces an innovative, highly efficient additive manufacturing technology known as extreme high-speed laser metal deposition (EHLMD). Finally, this paper summarizes the main difficulties involved in increasing the high-temperature wear resistance of LC-HEACs and some problems worthy of attention in the future development.

TEMPERATURE MONITORING FOR LASER METAL DEPOSITION USING NEAR-INFRARED SPECTROSCOPY

Temperature monitoring during laser metal deposition (LMD) aids process control to ensure high-quality production. However, the fluctuating emissivity of the melt pool limits the accuracy of the existing non-contact temperature measuring devices. Thus, this work explores a new temperature monitoring technique, where the thermal radiation emitted by the processing zone was collected with a near-infrared (NIR) spectrometer and fitted to Planck's law to determine the temperature. This work has established the optimised angle and distance of the fiber probe from the LMD processing area to maximise the spectral signal acquisition. The temperature determined from the technique was cross-validated with a thermocouple, resulted in a small deviation of 2.39%. The applicability of the spectroscopic method for continuous temperature monitoring of the LMD process has been demonstrated. The optimised placement for the fiber probe end was determined at the 45˚ angle relative to the surface of the substrate and positioned 5 cm away from the molten pool. The temperature during the LMD process decreased gradually then stabilised after approximately 17 mm track length, resembling those reports in prior studies. Our findings support the practicality of the proposed temperature monitoring approach in LMD.

The Aspects of Radiation Safety When Working With Ore from the Tomtor Integrated Rare Metal Deposit in Yakutia, Used as a Modifying Additive in Welding Materials

The results of measurements of the content of radioactive elements in ore samples from the Tomtor integral rare metal deposit are considered with the aim of safe use of ore with rare earth elements as a modifier of the weld pool during the processes of manual arc welding and fusing. It was revealed using a semiconductor gamma spectrometer that a significantly larger proportion of ionizing radiation activity is represented by the thorium-232 family. It is noted that natural concentrate is added to the composition of welding materials in very small quantities, and during welding operations in the room next to the welder, the values of the exposure dose rate will correspond to the initial radiation background in the room, therefore, both the welder and those people who will be in contact with the welded materials will not receive additional radiation dose to the natural background. It was concluded that the process of manufacturing the welding materials, welding, fusing and the use of welded structures are completely safe in terms of radiation.

The characteristics of S-wave velocity and mineralization of the “Double Domes” structure in the eastern Tethys Himalaya

The Tethys Himalayan belt in the southern Qinghai–Tibet Plateau has been intruded by a large amount of leucogranite due to collisional orogeny. In addition, strong tectonic movements since the Cenozoic era have led to the formation of a series of dome structures accompanied by various types of mineralization. The Cuonadong Dome and Yalaxiangbo Dome, forming the “double dome” structure in the eastern part of the Tethys Himalayan Belt, are affected by different geological processes, resulting in differences in their deep structures and affecting the formation of polymetallic minerals. At present, geophysical research on the fine structure of the crust of the “double dome” structure is limited, making it difficult to fully understand the formation of different deep structures in the Tethys Himalayan dome belt. This hinders the progress of research on the genesis of dome structures and large-scale mineralization mechanisms in continental collisional environments. In this study, the ambient noise tomographic method was used to obtain the S-wave velocity structure of the upper crust of the Cuonadong Dome and the Yalaxiangbo Dome, and the following results were found: 1. there is a significant difference in the velocity structures of the two domes, with the core velocity structure of the Yalaxiangbo Dome showing an overall high velocity, extending downward for more than 9 km, while the core of the Cuonadong Dome exhibits low-velocity characteristics, with some high-velocity bodies occurring locally, which may be related to the later intrusion of leucogranite and extensional activity of the Cuona Rift. 2. There are significant differences in the S-wave velocities between the lead–zinc deposits and rare metal deposits in the study area; the lead–zinc deposits occur in basins and graben margins and have large variations in the S-wave velocity, which may be related to the involvement of basin brine in mineralization; below the tungsten–tin–beryllium deposits, the S-wave velocity exhibits high-velocity protrusions, with mineralization occurring at the front ends of the protrusions, which may be caused by crystallization differentiation of leucogranite. 3. The study area has abundant geothermal resources and obvious geothermal structural features. The low-velocity basin in the upper part of the upper crust is a heat storage layer, the low-velocity channel in the middle is a heat-conducting layer, and the lower part is a low-velocity heat source area that continuously supplies heat, forming a special geothermal structural model for the Cuonadong Dome and Yalaxiangbo Dome.

Quantum-Sized Co Nanoparticles with Rich Vacancies Enabled the Uniform Deposition of Lithium Metal and Fast Polysulfide Conversion.

The notorious polysulfide shuttling and uncontrollable Li-dendrite growth are the main obstacles to the marketization of Li-S batteries. Herein, a dual-functional material consisting of vacancy-rich quantum-sized Co nanodots anchored on a mesoporous carbon layer (v-Co/meso-C) is proposed. This material exposes more active sites to improve its reaction performance and simultaneously realizes excellent lithiophilicity and sulfiphilicity characteristics in Li-S electrochemistry. As Li metal deposition hosts, v-Co/meso-C shows small nucleation overpotential, low polarization, and ultra-long cycling stability in both half and symmetric cells, as confirmed by experimental studies. On the S cathode side, experimental and theoretical calculations demonstrate that v-Co/meso-C enhances the adsorption of polysulfides and boosts their catalytic conversion rate. This, in turn, suppresses the shuttle effect of polysulfides and improves sulfur utilization efficiency. Finally, a shuttle-free and dendrite-free v-Co/meso-C@Li//v-Co/meso-C@S full cell is fabricated, exhibiting excellent rate performance (739 mAhg-1 at 5.0 C) and good cyclability (capacity decay rate is 0.033% and 0.035% per cycle at 2.0 and 5.0 C, respectively). Even a pouch cell with high sulfur loading (5.5mgcm-2) and lean electrolyte/sulfur (4.8µLmg-1) can still work 50 cycles with 80% capacity retention rate. This study shows far-reaching implications in the design of dendrite-free, shuttle-free Li-S batteries.

Impact of Samarium on Microstructural Evolution and Tribological Behavior of FeCoNiCr High-Entropy Alloys Fabricated by Laser Metal Deposition

Impact of Samarium on Microstructural Evolution and Tribological Behavior of FeCoNiCr High-Entropy Alloys Fabricated by Laser Metal Deposition

Influence of the inner roughness of powder channels on the powder propagation behavior in laser metal deposition

The powder propagation behavior of powder nozzles for the laser metal deposition process has a significant influence on powder utilization rate and track geometry. A well-focused powder stream will lead to a higher process efficiency and lower material loss. Powder channels with different roughness and a constant diameter of 1.5 mm were placed by wire electrical discharge machining into a copper alloy printed by powder bed fusion. Nickel base powder with a size of −106 to +45 μm was delivered through the powder channels with varied carrier gas flow rates and varied powder mass flow rates. High-speed imaging was used to analyze the powder flow. From these recordings, the dispersion angle of the powder stream from single channels could be measured as well as the velocity of particles. Moreover, the relationship between individual particle velocity and individual particle flight angle was investigated. It was found that the inner roughness of powder channels has a major impact on powder propagation behavior. It could be shown that with a decrease in Ra from 2.16 to 0.27 μm the divergence angle decreased by around 61% while the particle velocity was increased by at least 28% for all varied parameters. Particles with a high velocity tend to have a lower particle flight angle.