Alloy Deposition Research Articles

Influence of heat treatment on microstructure and tensile properties of selective laser melting metastable Ti55531-0.5Nb alloy

The deposition of metastable titanium alloys using additive manufacturing techniques is of increasing interest. The as-build samples generally require further subsequent heat treatment to control the microstructure and to meet the good comprehensive performance of structural components. In this study, the Ti55531-0.5Nb alloys fabricated by selective laser melting (SLM) technology after solution treatment were cooled in different modes to investigate the effect of cooling rates on microstructural evolution and tensile properties. The results indicate that the volume fraction of primary α decreases with the increase of cooling rate, while the secondary α displays the opposite trend. The high cooling rates increase the residual stresses in the sample, providing an additional driving force for phase precipitation during the aging process. In addition, all samples with different cooling rates exhibited high elongation (>10 %). The difference is that the Ti55531-0.5Nb alloys are more sensitive to changes in elongation than ultimate tensile strength (UTS) with variations in cooling rates. The UTS and elongation of the sample with solution plus water cooling and aging (STWC+AG) are 1185 ± 9 MPa and 10.3 ± 0.3 %, respectively, while the furnace cooling and aging (STFC+AG) sample exhibits a 71.4 % improvement in elongation at the expense of the UTS of 13.8 %. Furthermore, the fracture behavior of the samples exhibited a mixed fracture mechanism dominated by ductile fracture, and the ductile fracture is more prominent with the cooling rate decreases. The microscale shear band contributing to the elongation was found in the shear lip zone for the low cooling rate.

Fully Consolidated Deposits from Oxide Dispersion Strengthened and Silicon Steel Powders via Friction Surfacing

Abstract The objective of this work is to study the ability of friction surfacing to deposit metal alloys that are difficult to process with traditional methods. Creep and neutron irradiation resistant oxide dispersion strengthened (ODS) materials cannot be produced via conventional casting route due to insolubility of the oxidic and metallic alloy constituents, causing unintended inhomogeneous oxide dispersion and material behavior. Increasing silicon content of Iron-Silicon (Fe-Si) improves electromagnetic properties but embrittles the material significantly and the fusion based manufacturing methods unable to process this steel. The solid-state nature of the friction surfacing process offers a potential alternative processing route to enable wider usage of difficult to process alloy systems. Both ODS and Fe-Si materials are available in powder forms. While the existing literature in friction surfacing focuses on depositing composites by incorporating small quantities powders through holes in consumable rod, this is a first study that shows a large charge of powder can be converted to a homogeneous fully consolidated deposit in friction surfacing. A novel methodology is used that incorporates the high portion of powder feedstock into hollow consumable friction surfacing rods (up to 35% volume fraction). It was found that fully consolidated deposits can be produced with powder feedstocks using proposed methodology. A recrystallized, homogeneous, equiaxed microstructure was observed in Fe-Si 6.8 wt% and a new generation FeAlOY ODS alloy deposits processed with hollow stainless-steel friction surfacing rods. Both powder and rod material plasticize and deposit without bulk intermixing.

Low Current Density Cathode Plasma Electrolytic Deposition of Aluminum Alloy Based on a Bipolar Pulse Power Supply

The present paper reported a novel bipolar-pulse cathodic plasma electrolytic deposition (BP-CPED) technique with a low current density. This newly developed CPED technique can break down the barriers of the existing CPED technique with higher current density. In this report, ceramic coatings were successfully prepared on aluminum alloy via the BP-CPED technique in an aqueous carbamide-based electrolyte. Data recording results in the reacting process show that there is the current density of the cathode below 0.15 A/cm2 and that of the anode below 0.035 A/cm2, which approximately reaches the level of conventional MAO technique. Interestingly, the addition of PEG into the electrolyte can further reduce the current density and effectively improve the coating quality. The kinetic of the BP-CPED process was discussed based on the evolution of current density/voltage-time curves and spark discharge phenomena. SEM observations illustrate that BP-CPED coatings possess a typical porous-surface feature. XRD analysis indicates that the coating was mainly composed of Al2O3 and Al4C3. Al2O3/Al4C3/ZrO2 composite coatings fabricated after Zr-doping reflected the successful Zr-incorporation into the coating, which demonstrated that the BP-CPED technique can be used to design the coating composition by the doping modification. The direct pull-off and thermal shock tests confirmed that new BP-CPED coatings obtained under the cathodic plasma discharge have excellent bonding strength. It is possible that this novel BP-CPED technique can provide a promising choice in developing the large-area CPED surface treatment for the industrial application.

Microalloying design in directed energy deposition of complex-concentrated alloy: Pre-nitriding to inhibit hot cracking and promote mechanical properties

With the development of ultra-supercritical (USC) power generation technology, the increase of steam temperature puts higher requirements for high-temperature performance and processing reliability of superalloys. Here, a new complex-concentrated alloy (CCA) is developed for manufacturing the devices in USC circumstances. For the laser additive manufacturing of CCA, avoiding the hot cracking is crucial to guarantee reliable printability and favorable service performance. In this work, the nitrogen (N) is introduced innovatively by pre-nitriding powder to ensure sufficient N to combine with the matrix during the directed energy deposition process. The solidification temperature range can be narrowed to inhibit the hot cracking with the N-doping effectively. As a result, the sample with N-doping exhibited an extraordinary performance of strength (1083.51 MPa) and plasticity (20.83 %). The strengthening mechanisms mainly include solid solution strengthening, grain refinement strengthening, and dislocation strengthening. The elimination of defects leads to an increase in ductility in the meantime. In addition, the dynamic oscillation of the molten pool caused by pre-nitriding powder also has a nonnegligible impact on the breakdown of grain epitaxy growth and the initiation of grain refinement. These findings shed new light on the alloy design concept to inhibit hot cracking and promote mechanical properties.

Influence of thermal conductivity on evolution of grain morphology during laser-based directed energy deposition of CoCrxFeNi high entropy alloys

A model CoCrxFeNi high entropy alloy system was chosen to investigate the effect of thermal conductivity on the evolution of spatial orientation of columnar grain morphology during laser directed energy deposition. The thermal conductivity of the alloy was varied by tuning the chromium content in CoCrxFeNi alloys. CoCrxFeNi alloys with chromium content ranging between 0 and 24 at% were produced under identical processing conditions of laser direct energy deposition method. Electron back scattered diffraction images of the cross-sections revealed that the spatial orientation of grain morphology transitioned from zigzag columnar grains from layer-to-layer to near-continuous columnar grains across multiple layers with increased content of chromium in CoCrxFeNi. A multi-scale multi-physics finite element based thermo-kinetic model with consideration to multi-track multi-layer nature of the laser direct energy deposition technique was adopted to correlate the process thermo-kinetics with the evolution of microstructure. The computation calculations revealed that the decrease in thermal conductivity from 36 W/m.K (CoFeNi) to 26 W/m.K (CoCr24FeNi) at the melting point reduced the cooling rate from 3.3 ×104 °C/s to 1.3 ×104 °C/s in CoFeNi and CoCr24FeNi alloys, respectively. This subsequently evolved into increased degree of remelting of previously deposited layers and caused the direction of resultant thermal gradient to reorient towards the build direction. Such reorientation in resultant thermal gradient contributed to transition of spatial orientation of grain morphology from columnar zigzag microstructures from layer-to-layer to near continuous columnar grains across multiple layers. The present observation was verified compared with other reported metallic systems exhibiting zigzag and continuous columnar grains, and a unified mechanism underlining the role of thermal conductivity on microstructure evolution was proposed.

Preparation of MoSi2-particle reinforced Ni-W alloy coatings and their anti-corrosion behavior in CO2-saturated 3.5 % NaCl solution

In the process of oil and gas production, the use of Ni-W electroplated coatings as a protective layer for oil well tubing has been widely used. In this study, the effect of MoSi2 particles as reinforcing material on the properties of electrodeposited coatings was investigated in order to improve the resistance of Ni-W alloy deposits against CO2 corrosion. The purchased MoSi2 sample was subjected to detailed material characterization, including microscopic morphology, crystallographic properties, particle size distribution and dispersion in the plating solution. After the introduction of MoSi2 particles into the deposits, the diffuse phase strengthening mechanism improved the properties of alloy. By comparing the electrochemical behavior of 3.5 % NaCl solution in saturated CO2, it can be concluded that the composite coatings prepared have the best corrosion resistance when MoSi2 is added to the plating solution at 0.02 g/L. This study provides new horizons for the application of Ni-W coatings in CO2-rich environments or CCUS conditions.

Hierarchically heterogeneous microstructure and mechanical properties in laser-directed energy deposition of γ-TiAl alloy through intrinsic cyclic heat treatment

The complex thermal effects of laser direct energy deposition (L-DED) provide significant advantages for production of high-performance γ-TiAl alloy, whereas challenges still exist in microstructure tailoring and mechanical properties. This work focuses on the influence of intrinsic cyclic heat treatment (ICHT) on the evolution of microstructures and mechanical properties in different building height regions of an L-DED TiAl alloy thin-wall sample. The results indicate that ICHT induces discontinuous coarsening (DC) effects by consuming the lamellar interface energy of the initial lamellae, resulting in grain refinement. With the increase in building height, the thermal accumulation leads to an increase in the initial lamellar spacing, which weakens the DC effect. At the top, insufficient thermal cycles prevent fine grain growth and erode coarse grains, hindering overall grain refinement. Ultimately, the hierarchically heterogeneous microstructure forms in the L-DED TiAl alloy, including refinement of hierarchical lamellar colony structure decorated with fine (α2+γ) lamellar structure and (α2+6H-LPS) lamellar structure (6H-LPS refers to 6H long-period structure phase). Specifically, the bottom region exhibits the best combination of ultimate tensile strength (706 ± 33 MPa) and strain (0.68 ± 0.05 %). The high tensile strength can be attributed to the hindrance of dislocation movement by the fine lamellae and the 6H-LPS phase ,caused by the high cooling rate of L-DED, while the elongation is attributed to the reduction in crack propagation energy due to the presence of fine grains.

Effect of Electrolysis Conditions on Electrodeposition of Cobalt-Tin Alloys, Their Structure, and Wettability by Liquids.

The aim of this study was a systematic analysis of the influence of anions (chloride and sulfate) on the electrochemical behavior of the Co-Sn system during codeposition from gluconate baths. The pH-dependent multiple equilibria in cobalt-tin baths were calculated using stability constants. The codeposition of the metals was characterized thermodynamically considering the formation of various CoxSny intermetallic phases. The alloys obtained at different potentials were characterized in terms of their elemental (EDS and anodic stripping) and phase compositions (XRD), the development of preferred orientation planes (texture coefficients), surface morphology (SEM), and wettability (water; diiodomethane; surface energy). The mass of the deposits and cathodic current efficiencies were strongly dependent on both the deposition potential and the bath composition. The morphology and composition of the alloys were mainly dependent on the deposition potential, while the effect of the anions was less emphasized. Two-phase alloys were produced at potentials -0.9 V (Ag/AgCl) and lower, and they consisted of a mixture of tetragonal tin and an uncommon tetragonal CoSn phase. The preferential orientation planes of tin grains were dependent on the cobalt incorporation into the deposits and anion type in the bath, while the latter did not affect the preferential orientation plane of the CoSn phase. The surface wettability of the alloys displayed hydrophobicity and oleophilicity originating from the hierarchical porous surface topography rather than the elemental or phase composition. The codeposition of the metals occurs within the progressive nucleation model, but at more electronegative potentials and in the presence of sulfate ions, a transition from progressive to instantaneous nucleation can be possible. This correlated well with the partial polarization curves of the alloy deposition and the texture of the tin phase.

ВЛИЯНИЕ ТЕРМОДИНАМИЧЕСКИХ ПАРАМЕТРОВ ПЛАЗМЕННОЙ СТРУИ НА АДГЕЗИОННУЮ ПРОЧНОСТЬ ГАЗОТЕРМИЧЕСКИХ ПОКРЫТИЙ

Gas-thermal spraying of metals and alloys makes it possible to obtain coatings with high performance properties on the surfaces of parts. These coating methods can be effectively used in the restoration of worn-out parts of machines and equipment of various types, which, in the face of large-scale sanctions, is one of the most important tasks of technological independence of Russian industries. (Research purpose) The research purpose is searching for the regularities of the influence of the main thermodynamic parameters of the plasma jet on the adhesive strength of the formed coatings. (Materials and methods) The deposition of refractory metals and alloys on a graphite substrate was carried out using the UPU-3 plasma installation. The temperature and velocity of the particles during plasma spraying of the wire were determined according to the generally accepted method. The average mass temperature of the particles in the considered section of the plasma jet was estimated by the increment of the enthalpy of the particles of the deposited metal. When calculating the heating temperature of the particles of the sprayed powder material, it was assumed that the temperature field of the gas stream beyond the nozzle section is determined by the thermophysical properties of plasma-forming gases and the conditions of heat exchange of the jet with the environment. The adhesive strength of the coatings was measured by the shear method. To estimate the values of residual stresses, temperature fields in the deposited layer and substrate were studied. (Results and discussion) The existing theoretical ideas about the physical processes in the formation of gas-thermal coatings were analyzed. The main thermophysical characteristics of the plasma jet affecting the sputtering of various powder and wire materials were considered. The factors ensuring the maximum adhesion strength of gas-thermal coatings to the surface of the composite material were determined. (Conclusions) It has been proved that the temperature of the particles of the sprayed material determines the adhesion strength of the coatings. The magnitude of thermal stresses occurring in coatings depends on the ratio of the thermophysical constants of the coating material and the substrate. To obtain coatings with maximum adhesive strength during high-temperature spraying of the material, it is necessary to additionally take into account the conditions determined by the forces of mechanical engagement of deforming particles.

Tribology-driven strategies for tool wear reduction and surface integrity enhancement in cryogenic CO2-cooled milling of laser metal deposited Ti64 alloy

Additive manufacturing (AM) is chosen for its ability to streamline production processes and design freedom. This reduces material waste, enables rapid prototyping, and facilitates intricate geometries, ultimately offering cost-effective and customizable solutions for manufacturing complex components in diverse industries. Overlapping melting trajectories result in a low-quality surface (Ra=∼13.34 µm) in the laser metal deposition (LMD) of the Ti64 alloy. Therefore, post-processing is often essential for AMed parts for engineering applications. Milling trials were conducted on AMed specimens under four environmental conditions: dry, flood, minimum quantity lubrication (MQL), and cryogenic medium. The machinability was evaluated in terms of the cutting temperature, machined surface roughness, tool wear, chip morphology, and microhardness. The flank wear under cryogenic CO2 condition is 52.78–54.29 % lower than dry condition, 33.86–36.24 % lower than flood cutting, and 23.64–26.86 % lower than MQL. The outcomes show that cryogenic cooling augments the tool life and the surface integrity of milling LMD parts. Moreover, the hardness under cryogenic CO2 was higher, indicating dimensional stability and maintenance of shape integrity under applied loads.

Laser deposition of aluminum and magnesium‑based alloys for repair and surface restoration of components

The results of studying the processes of laser deposition of aluminum and magnesium‑based alloys, the features of the structure of deposited layers using electron microscopy and X‑ray computed tomography data, measurements of microhardness after laser deposition of aluminum and magnesium alloys are presented. Modeling of the stress‑strain state of flat components during laser deposition of an aluminum‑magnesium alloy containing 0.6–0.95 % magnesium, 0.7–1.0 silicon, up to 0.3 titanium, up to 0.5 zinc, and up to 0.4 % manganese was performed. The nature of the distribution of deformations and stresses during the use of various technological schemes of laser deposition during surface treatment of aluminum‑magnesium alloys by laser deposition methods is established.

Investigation on the Microstructure and Mechanical Properties of Multi-layer and Multi-pass Al Alloy Deposition Based on Cold Metal Transfer Technology

Investigation on the Microstructure and Mechanical Properties of Multi-layer and Multi-pass Al Alloy Deposition Based on Cold Metal Transfer Technology

C3N5 nanosheets decorated with Cu–Pt alloy nanoparticles toward efficient photocatalytic hydrogen evolution

The construction of highly efficient photocatalysts for generating high-purity hydrogen (H2) through a sustainable water decomposition system is a feasible option to replace conventional non-renewable energy resources. Here, we report a simple chemical reduction approach to embed Cu–Pt alloy nanocrystals on the C3N5 (CN) matrix, creating a Schottky heterojunction. The structural morphology, crystal phase, light-harvesting capacity, and photo-electrochemical properties of as-prepared heterostructures were investigated. The uniformly anchored Cu–Pt alloy nanocrystals improve the photocatalytic H2 evolution (PHE) activity by promoting the separation and transfer of photogenerated carriers and inhibiting recombination. Meanwhile, the alloyed nanocrystals strengthen the absorption of incident light energy, inducing photothermal energy. This improves the charge carrier separation and promotes the surface reaction kinetics. The PHE performance of as-developed catalysts could be adjusted by optimizing the molar ratio of Cu/Pt ions. Among them, the optimal Cu1Pt3/CN photocatalyst yields a higher PHE performance (672.85 μmol g−1 h−1). Notably, the Cu1Pt3/CN catalyst also reveals an enhanced photocatalytic activity for H2 evolution in natural seawater. The possible PHE mechanism in CuPt/CN heterostructures is discussed toward the role of CuPt alloy deposition in boosting photocatalytic efficiency.

Optimization of Laser-Wavelength Dependence for Open-Air Atmospheric Pressure Pulsed Laser Deposition of AlCrFeMnTi High-Entropy Alloy for Tailored Surface Properties.

High-entropy alloys (HEAs) have garnered significant attention in different fields due to their exceptional mechanical and physical properties, making them promising candidates for various applications. Several techniques, including physical vapor deposition and pulsed laser deposition (PLD), have been employed for the fabrication of HEA thin films. In this study, we explore a novel approach to synthesizing the lightweight HEA (LWHEA) AlCrFeMnTi using PLD in air at atmospheric pressure with a particular focus on the influence of the laser wavelength on the deposition process and the resulting alloy characteristics. This research investigates the impact of different laser wavelengths on the LWHEA's characterization and the optimization of laser wavelength dependence in air at atmospheric pressure PLD of LWHEA AlCrFeMnTi for tailored surface properties such as phase composition, microstructure, and corrosion resistance. Systematically varying the laser wavelength was attempted to optimize the deposition conditions. This was aimed at achieving enhanced properties and precise control over the alloy's composition. This work contributes to a deeper understanding of the open air PLD process for LWHEAs and sheds light on the role of the laser wavelength in tailoring their properties, which can have significant implications for the development of advanced materials for aerospace, automotive, and other high-performance applications. Ultimately, this research aims to provide valuable insights into the design and fabrication of LWHEAs with tailored properties through laser-based deposition techniques.

In-situ monitoring of additive friction stir deposition of AA6061: Effect of rotation speed on the microstructure and mechanical properties

The AA6061 alloy depositions fabricated under three rotation speeds (Ω, 450, 500 and 550 rpm) are obtained by the additive friction stir deposition (AFSD) technique in this study. The real-time temperature, force and torque during the AFSD process were monitored by a self-developed process-aware kit, helping to thoroughly investigate the influence of Ω on the microstructure and mechanical properties of the depositions. Combined with the results of the electron back scattered diffraction (EBSD) analysis on a large area (4 × 4 mm2), it is found that the grain size increases with the increase of Ω due to high heat generation. The proportion of deformation texture components reduces because of the lower strain distribution as well as the slight deformation behavior. A higher average micro-hardness is found on the 550 rpm-deposition because of the dislocation strengthening effect. Furthermore, the values of yield strength (87.8 MPa) and ultimate tensile strength (147.2 MPa) of the depositions are the highest when the Ω is the lowest (450 rpm), owing to the lowest thermal cycle. All the results are intended to provide useful guidance and a theoretical basis for producing high-performance Al-based alloys through AFSD.

The induced co-deposition of Ni–Mo–W ternary alloy; Coatings for hardness and corrosion resistance applications

Ni–Mo–W ternary alloy coatings were electrodeposited on mild steel substrate using citrate electrolyte for hardness and corrosion resistance applications. The influences electrolyte pH, electrolyte temperature and sodium molybdate concentrations on deposit qualities were studied. The sodium molybdate concentrations were varied from 0.025 to 0.1 M for obtaining alloy coatings with various molybdenum (Mo) compositions. The deposition condition such as electrolyte concentration, pH and temperature were optimized for obtaining good aesthetic (bright) appearance, surface stability and microhardness properties. The maximum Mo composition (47.71 wt %) in alloy deposit was achieved is 47.71 wt % using 0.1 M sodium molybdate concentration. The microhardness properties were increased from 850 HV to 946 HV by introducing molybdenum (47.71 wt %) as third alloying element in to Ni–W alloy matrix. The obtained mechanical and corrosion resistance properties of these ternary alloy coatings were compared with binary alloy and metallic coatings viz., Ni–W and Ni–Mo and metallic Ni coatings. The superior corrosion rate was observed for Ni–Mo–W alloy deposits (5.8 mpy) compared to Ni–W (9.04 mpy) and Ni–Mo (8.89 mpy) alloy.

Directed Energy Deposition of Metal Alloys

Directed energy deposition (DED) stands as an advancement in material utilization, facilitating the production of highly precise near-net shape components using wire and powders [...]

Solid-state deposition of Mo-doped CoCrFeNi high-entropy alloy with excellent wear resistance via cold spray

To improve the wear resistance of CoCrFeNi high-entropy alloys (HEAs) for a wider range of industrial applications, the alloying strategy was applied to CoCrFeNi HEA by doping Mo element in various ratios, and CoCrFeNiMox (x = 0, 0.2, 0.5, and 1.0) HEA deposits were fabricated by cold spray. The microstructure evolution, mechanical properties, and tribological properties of cold-sprayed CoCrFeNiMox HEA deposits were systematically investigated. The results showed that Mo0, Mo0.2, and Mo0.5 deposits have a face-centered-cubic (FCC) single structure, while Mo1.0 deposit was composed of FCC matrix and hard brittle phases. The doping of Mo element into CoCrFeNi HEA deposits significantly increased the hardness due to the enhanced solid solution strengthening and precipitation strengthening. As a result, the anti-wear properties of Mo-doped CoCrFeNi HEA deposits were gradually improved with the increase in Mo ratios. To be specific, the Mo1.0 deposit exhibited the lowest specific wear rate of 5.1 × 10−5 mm3/N·m, which was reduced by 94.9% in comparison to the Mo0 deposit. Overall, the current study proposes a new strategy to manipulate the mechanical properties of cold-sprayed HEA deposits by alloying.

Fabrication of Cu-Ni Alloy Microcomponents using Localized Electrochemical Deposition

With the rapid development of electronics, additive manufacturing of complex three-dimensional microscale metal and alloy structures has emerged as one of the future directions for advanced technologies. In this study, a localized electrochemical deposition technique was developed which enables the fabrication of microscale three-dimensional metal structures in an ambient environment. Notably, we investigated the effects of voltage, initial electrode gap, and electrolyte composition on the deposition of Cu-Ni alloy. Furthermore, we successfully fabricated Cu-Ni equiatomic micro-columns, providing possibilities for the micro/nanoscale fabrication of commercial K-Monel copper. Finally, based on these foundations, we successfully shaped overhanging structures with various angles as well as an “H” structure using a rotating cathode substrate, demonstrating their potential in the fabrication of Cu-Ni alloy micro components.

Enhanced surface finish and reduced porosity of TiC nanoparticles reinforced 2219 aluminum alloy deposit fabricated via oscillating laser-arc hybrid additive manufacturing

Additive manufacturing (AM) of ceramic particle reinforced aluminum alloy has drawn increasing attention due to the refined microstructure and improved mechanical properties in as-deposited condition. However, it is still challenging to make defect-free ceramic particle reinforced aluminum alloy deposit with desirable surface finish using wire-based AM technique because of the special thermophysical properties of the incorporated ceramic particles. In this work, a novel oscillating laser-arc hybrid additive manufacturing (OLHAM) technique was developed to fabricate TiC nanoparticles reinforced 2219 aluminum alloy deposit. The surface finish and porosity were evaluated using optical microscope and 3D XCT, respectively. Compared with wire-arc additively manufactured (WAAMed) deposit, the surface roughness and volume porosity of OLHAMed deposit decreased by 46.0 % and 88.3 %, respectively. In-situ high-speed photography was used to observe the arc and molten pool behaviors to understand the mechanism of enhanced surface finish and reduced porosity. The enhanced surface finish was attributed to smaller layer width fluctuation and higher arc stability, which resulted from the action of the hybrid heat source. The elimination of large droplet transfer, which caused pores in the WAAMed deposit, and the promotion of molten pool fluidity resulted in much lower porosity of the OLHAMed deposit.