Microstructure Of Deposits Research Articles

Deposition mechanism of alumina particles in aerosol deposition based on the kinetic energy of particles

In this study, the aerosol deposition process was used to deposit the α-Al2O3 coating on Mo substrate under various conditions, i.e., particle size, type of carrier gas, gas flow rate and a nozzle–substrate distance. The formation behaviors of the α-Al2O3 coating in terms of deposition rate, microstructure and texture were studied in a correlation with the kinetic energy of the particles forming the coating. The fully dense and crystalline α-Al2O3 coatings were observed with the average grain size of 20 nm, significantly smaller than the particle sizes of 0.14 and 1.0 μm. The coating layers under all conditions were examined with a fiber texture with the (0001) plane tilted about 15° away from the coating plane. The microstructure and texture formation were resulted by fragmentation and plastic deformation of the particles during the deposition. The deposition formation of the particle collisions with the coating was simulated by the finite element analysis with the fragmentation model. The model suggested that the particles fracture at the boundary of the maximum shear strain generated by the particle impact. The deposit is formed by the lower part of the fracture particle. The strain energy in the deposited area of retained particles is considered to be equivalent to the kinetic energy, which includes the effects of the particle characteristics and physical properties. The result indicated that the changes of the deposition rate and texture formation can be well explained as a function of the strain energy. Regardless of the strain energy, the density of the α-Al2O3 coatings was almost the same as that of the bulk α-Al2O3 material. It was found that the high strain energy can lead to both high deposition rate and high indentation hardness.

Effect of shot peening on electrophoretic deposition of bioactive glass coating on AISI 316L stainless steel

Bioactive glass coating of SiO2–CaO–P2O5 was synthesized and deposited on shot peened stainless steel AISI 316L substrates through electrophoretic deposition. Shot peening is known to enhance the fatigue properties of the substrate material; however, the present study aims to investigate how this prior shot peening can affect on the electrophoretic coating properties and performance. Shot peening was carried using two different sets of parameters as conventional shot peening (Almen intensity: 15A and coverage:100%), and severe shot peening (Almen intensity: 7C and coverage:1500%). The coated samples were studied regarding deposition thickness, microstructure, macrotexture and surface roughness, as well as wettability with contact angle tests. Corrosion behavior was also investigated using potentiodynamic polarization and electrochemical impedance spectroscopy in simulated body fluid solutions at 37 °C. The results confirmed that the coating thickness decreased from 55.3 μm for CNP to 27 μm and 9.5 μm for CCSP and CSSP respectively. Shot peening applied before electrophoretic deposition modulated the wettability and corrosion resistance of the coated samples through variation of roughness and the extent of grain refinement. As well as, the water contact angle of CSSP sample was equal to 15.64° which is much lower than CNP (55.3°). Also, the amount of coated samples’ corrosion rate changed by this order CCSP (1.91 × 10−2)>CNP (1.31 × 10−2)>CSSP (1.07 × 10−2). The high surface energy on shot peened samples caused the smaller BG grain size deposited on surfaces. The amount of BG grain size of each sample is as follow CNP 2.12 ± 1.6 μm, CCSP 1.34 ± 0.8 μm and CSSP 0.81 ± 0.3 μm.

Oriented growth of cobalt electrodeposits assisted by an interfacial flow of bubbles

High-quality Co products are desirable for a variety of applications due to its unique properties. Herein, an interfacial field of flowing bubbles was used to modify the microstructure of Co deposits in the electrowinning process. The effect of flowing bubbles on morphology, crystallographic structure and impurities of Co deposits were investigated. The nucleation and growth of Co deposits were discussed based on chronoamperometric experiments and sampling experiments. The results indicated that the microstructure of Co deposits was effectively modified by an external field of flowing bubbles. The Co deposits prepared in a quiescent electrolyte were porous and inhomogeneous, while the deposits prepared by using the flowing bubbles were compact and uniform. The nucleation and growth modes of Co deposits were also altered by the flowing bubbles. Preferentially oriented grains in the (110) direction were formed by instantaneous nucleation and screw dislocation growth of the deposits. Improvements in microstructure and crystallographic orientation were able to enhance the purity of Co deposits.

Influence of active cooling on microstructure and mechanical properties of wire arc additively manufactured mild steel

Additive manufacturing (AM) of metals attracts attention because it can produce complex structures in a single step without part-specific tooling. Wire arc additive manufacturing (WAAM), a welding-based method that deposits metal layer by layer, is gaining popularity due to its low cost of operation, feasibility for large-scale part fabrication, and ease of operation. This article presents the fabrication of cylindricalshaped mild steel (ER70S-6) samples with a gas metal arc (MIG)—based hybrid WAAM system. A mechanism for actively cooling the substrate is implemented. Deposition parameters are held constant to evaluate the impact of active cooling on deposition quality, inter-pass cooling time, and internal defects. Surface and volume defects can be seen on the cylindrical sample fabricated without an active cooling setup. Defect quantification and phase analysis are performed. The primary phase formed was α-iron in all samples. Actively cooled deposition cross section showed a 99% decrease of incomplete fusion or porosity, with temperature measured 60 s after deposition averaging 235°C less than non-cooled. Microstructural analysis revealed uniformity along the build direction for actively cooled deposition but non-uniform microstructures without cooling. Hardness decreased by approximately 22HV from the first layer to the final layer in all cases. Property variation can be attributed to the respective processing strategies. The current study has demonstrated that active cooling can reduce production time and porosity while maintaining uniform microstructure along the build direction. Such an approach is expected to enhance the reliability of WAAM-processed parts in the coming days.

Effect of NbC inoculants on the elastic properties and microstructure of additively manufactured IN718

In this study, the effects of NbC inoculants on the elastic properties and microstructure of laser blown powder-directed energy deposition (LBP-DED) IN718 are investigated. The addition of the NbC particles increased the volume fraction of MC-type carbides and decreased that of the Laves phase. It was found that the inoculant containing samples exhibited a marginally increased hardness and an enhanced Brass texture component {110} 〈211〉. The occurrence of this textural enhancement is theorised to be a result of the NbC restricting dendritic growth along specific directions during build. The addition of the inoculant therefore offers a method of achieving a degree of microstructural and textural control during additive manufacturing.

Effects of bath parameters on structure characteristic of Ni-W Electrodeposited alloy

This study describes the effects of the bath parameters (temperature, current density, additive concentrations and stirring) on tungsten content and microstructures of Ni-W deposits prepared from thiourea-containing bath, on graphite substrate to protect it from oxidation at high temperature. The morphology of the deposits was studied by optical microscope (TEM) and the approximate composition by energy dispersive spectroscopy (EDS).Increasing the concentration of thiourea refining the structure of the deposits, while the increasing in the current density and temperature led to increase the W content with and without stirring.

Study on Pulse-Reverse Electroplating Process for the Manufacturing of a Graphene-Based Coating.

This work investigates the feasibility of increasing the electric conductivity of an AA1370 aluminium wire by using pulse-reverse electrodeposition to realize Cu-Graphene composite coating. The graphene adopted was in the form of nanoplates (GnP). To study the effects of plating parameters, a 23 factorial plan was developed and tested. During the tests, the following process parameters were varied: the current density, the frequency and the duty cycle. The ANalysis Of VAriance (ANOVA)) was adopted to evaluate their influence on the coated wires' morphology and electrical conductivity resistance. The results show that all the tested conditions allow good compactness to the coating, and the amount of graphene is well incorporated within the microstructure of the copper deposit. In addition, in the best conditions, the electrical resistivity decreases up to 3.4% than the uncoated aluminum.

Optimizing mechanical properties and Ag ion release rate of silver coatings deposited on Ti-based high entropy alloys

This paper details the characterization of microstructure, texture, mechanical properties, and ion release behavior of antibacterial Ag thin films sputtered on two novel biomedical high entropy alloys (HEAs), namely the Ti23Ta10Hf27Nb12Zr28 (HEATi23) and Ti28Ta10Hf30Nb14Zr18 (HEATi28) alloys. Specifically, the influences of varying deposition time and Ar flow rate were investigated to reveal the mechanisms dictating the microstructure, texture, and mechanical properties of the coatings. In addition, static immersion experiments were carried out in simulated body fluid (SBF) for 28 days to establish the relationship between ion release from the coatings and the deposition parameters, microstructure, and surface texture. It was shown that texture evolution in Ag thin films depends on both film thickness and Ar flow rate, such that there exists a critical thickness at which the energy minimization mechanism is altered. A very good correlation was also observed between an increase in (111) peak intensity and a decrease in released Ag ion fraction. Overall, the findings of the work presented herein suggest that the alterations in Ag deposition parameters could be optimized to obtain the desired mechanical properties while enhancing the biocompatibility of the HEA substrates by coating them with antibacterial Ag films.

Ductile and high strength Cu fabricated by solid-state cold spray additive manufacturing

• Pure Cu shows the UTS of 271 MPa and elongation to fracture of 43.5% without additional post-treatments. • Cold spray additive manufacturing can achieve combination of high strength and good ductility • The deposit microstructure shows a gradient nano-grain structure with bimodal size distribution. • The gradient nano-grained (GNG) structure in single splat composes the deposit microstructure. • The balance between work hardening and thermal softening determine the performance. In this work, pure Cu with excellent strength and ductility (UTS of 271 MPa, elongation to fracture of 43.5%, uniform elongation of 30%) was prepared using cold spray additive manufacturing (CSAM), realizing a breakthrough in the field. An in-depth investigation was conducted to reveal the microstructure evolution, strengthening and ductilization mechanisms of the CSAM Cu, as well as the single splats. The results show that the CSAM Cu possesses a unique heterogeneous microstructure with a bimodal grain structure and extensive infinitely circulating ring-mounted distribution of twinning. Based on the single splat observation, the entire copper particle forms a gradient nano-grained (GNG) structure after high-speed impact deposition. The GNG-structured single splat serves as a unit to build the heterogeneous microstructure with bimodal grain distribution during the successive deposition in CSAM. The results also show that CSAM can achieve synergistic strengthening and ductilization by controlling the grain refinement and dislocation density. This work provides potential for CSAM technique in manufacturing various metallic parts with the desired combination of high strength and good ductility without additional post-treatments.

Behaviour of single-crystal nickel alloy in the conditions of high-temperature hydrogen corrosion

This study presents the results of the investigation of the behaviour of ZhS32-VI single-crystal nickel alloy in hydrogen environment or argon atmosphere at 850°C. The microstructure and chemical composition of corrosion deposits were studied by scanning electron microscopy and X-ray energy-dispersive analysis. It has been established that in argon containing an admixture of oxygen a dense scale rich in cobalt and nickel oxides is formed. At atmosphere containing 65% hydrogen and 35% argon an increased content of aluminum in the surface composition was noted. The influence of 100% hydrogen leads to segregation of tungsten and rhenium with the formation of convex growths. The data of simultaneous thermal analysis revealed that the amount of desorbed hydrogen can be from 0.08 to 0.14%.

Microstructure and mechanical properties of wire-fed arc-based directed energy deposition of high-strength steel after ultrasonic impact oxidation treatment

The ultrasonic impact oxidation treatment (UIOT) was applied to the local region of a high-strength steel specimen fabricated via a wire-arc directed energy deposition (DED) process. The microstructure and shear-punch strength of the specimen were investigated. The effects of temperature on the UIOT were also studied. Results show that UIOT produces an oxide layer on the treated surface and the elements in the pin are transferred to form the oxides. UIOT at room temperature results in the highest element transfer amount from the pin. The UIOT-induced oxides become tiny oxide inclusions dispersed in the DEDed specimen. Contents of Al, Si, Ti, Mn, and O of the inclusions are significantly higher than those in the deposited metal and the Mn-deplete zone is generated near the inclusion, which has the favorite conditions for the nucleation of acicular ferrite. The UIOT results in finer grains in the treated region than those in the untreated region, and it decreases the strength of the treated material while increasing the equivalent yielding-to-tensile ratio.

Clarifying the Relationship between the Lithium Deposition Coverage and Microstructure in Lithium Metal Batteries.

Improving the reversibility of lithium metal batteries is one of the challenges in current battery research. This requires better fundamental understanding of the evolution of the lithium deposition morphology, which is very complex due to the various parameters involved in different systems. Here, we clarify the fundamental origins of lithium deposition coverage in achieving highly reversible and compact lithium deposits, providing a comprehensive picture in the relationship between the lithium microstructure and solid electrolyte interphase (SEI) for lithium metal batteries. Systematic variation of the salt concentration offers a framework that brings forward the different aspects that play a role in cycling reversibility. Higher nucleation densities are formed in lower concentration electrolytes, which have the advantage of higher lithium deposition coverage; however, it goes along with the formation of an organic-rich instable SEI which is unfavorable for the reversibility during (dis)charging. On the other hand, the growth of large deposits benefiting from the formation of an inorganic-rich stable SEI is observed in higher concentration electrolytes, but the initial small nucleation density prevents full coverage of the current collector, thus compromising the plated lithium metal density. Taking advantages of the paradox, a nanostructured substrate is rationally applied, which increases the nucleation density realizing a higher deposition coverage and thus more compact plating at intermediate concentration (∼1.0 M) electrolytes, leading to extended reversible cycling of batteries.

Influence of assisted longitudinal magnetic field on the microstructure and mechanical properties of ER2319 aluminium alloy parts fabricated by wire and arc additive manufacturing

The deposit morphology, microstructure, and mechanical properties of wire and arc additive manufacturing (WAAM) of ER2319 aluminium alloy with and without assisted longitudinal magnetic field (ALMF) were investigated comprehensively and comparatively in this study. The results showed that the ALMF improved the surface forming accuracy slightly, and effectively promoted the equiaxed transformation of grains. Simultaneously, the introduction of ALMF is beneficial to improving the morphology and distribution of the strengthening phase and reducing the tendency of intergranular corrosion caused by the segregation of Cu elements along the grain boundaries. Moreover, ALMF can remarkably reduce the generation rate of large pores, thereby effectively improving the tensile strength of the deposits and reducing the anisotropy of mechanical properties.

Influence of spray parameters on particle deposition behaviour, microstructure, phase constitutions, and mechanical properties of high velocity oxy-fuel sprayed WC-Cr3C2-Co coatings

To optimise spray parameters for fabricating well-bonded and less decarburised coatings, the morphologies and cross-sectional microstructures of powders and splats, in addition to the microstructure, phase constitution, and mechanical properties of high-velocity oxy-fuel (HVOF)-sprayed WC–Cr3C2–Co coatings were systematically investigated. Significantly influenced by spray parameters, splat morphologies vary from ellipsoids to well-flattened pies with some ejectors or stripes on their periphery and a splat/substrate interface with good contact. Splat microstructures vary homogeneously from a minimal hard phase to non-uniform structures with some dense surface layers and smoothly outlined hard phases or to non-uniform structures with rough surfaces and angular hard phases. The coating microstructure evolves from a non-lamellar structure with many pores to a lamellar structure with a well-contacted interface and a smooth surface hard phase. The coatings mainly consist of the WC hard phase and a small fraction of decarburised and amorphous phases, in addition to Co, Cr3C2, Cr7C3, Cr2O3, and Cr2O5. Porosity and WC retention index vary from 0.89 ± 0.11 to 2.32 ± 1.75% and from 84.68 to 94.48%, respectively. Microhardness, elastic modulus, fracture toughness, adhesive strength, and wear rate of the coatings vary from 7.03 ± 0.64 to 11.96 ± 0.94 GPa, from 77.64 ± 13.77 to 244.73 ± 65.75 GPa, from 1.23 ± 0.1 to 2.66 ± 0.66 MPa m1/2, from 18.54 ± 1.21 to 63.84 ± 8.01 MPa, and from 1.38 ± 0.32 to 3.54 ± 0.79 × 10−2 mg/(N⋅m), respectively.

Constructing Three-Dimensional Topological Zn Deposition for Long-Life Aqueous Zn-Ion Batteries.

Uniform and compact Zn deposition-dissolution is essential to achieve high Coulombic efficiency and long lifespan for Zn anodes. More attention has been commonly focused on the suppression of macroscopic Zn dendrites in the previous reports. The rational control of the microstructure of Zn deposition to prevent the intrinsic volume expansion and pulverization of Zn metal so as to stabilize Zn anodes is less discussed. Herein, we construct a three-dimensional topological Zn deposition at the nanoscale through an in situ electrochemical process in the optimal hybrid aqueous electrolyte. The topological electrode structure can efficiently accommodate microscopic strain and volume variation and thus largely preserve the macroscopic integrity and electrical contact of Zn anodes, leading to enhanced reversibility and stability. With the unique topological structure of Zn deposition, the Coulombic efficiency of Zn anodes could reach >99.9% with excellent cycling over 1182 h at 2 mA cm-2 and 2 mA h cm-2 (Zn utilization: 11.4%). The evolution of "dead" Zn during repeated cycling is first investigated using a homemade semiquantitative analysis method to determine the critical "short slab" for aqueous Zn batteries under the practical application. This work provides an insightful method to regulate the microscopic morphology of Zn deposition for high-performance Zn batteries.

Rapid Microstructure Homogenization of a Laser Melting Deposition Additive Manufactured Ti-6.5Al-3.5Mo-1.5Zr-0.3Si Alloy by Electropulsing.

The typical microstructure of the laser melting deposition (LMD) additive-manufactured Ti-6.5Al-3.5Mo-1.5Zr-0.3Si alloy (TC11) contains the heat-affected bands (HABs), the narrow bands (NBs) and the melting pools (MPs) that formed due to the reheating and superheating effects during the layer-by-layer manufacturing process. Characterization results indicated that the coarse primary α lath (αp) and transformed β (βt) structures were located in the HABs, while the fine basketweave structure was formed inside the MPs. The rapid modifications of microstructure and tensile properties of the LMD-TC11 via electropulsing treatment (EPT) were investigated. The initial heterogeneous microstructure transformed into a complete basketweave structure and the HABs vanished after EPT. Thus, a more homogeneous microstructure was achieved in the EPT sample. The ultrafast microstructural changes were mainly attributed to the solid state phase transformation during electropulsing. The tensile properties of the sample were basically stable, except that the yield strength decreased as EPT voltage increased. This study suggests that EPT could be a promising method to modify the microstructure and mechanical properties of the additive-manufactured alloys in a very short time.

Laser‐Directed Energy Deposition Additive Manufacturing of Nickel–Titanium Coatings: Deposition Morphology, Microstructures, and Mechanical Properties

To overcome the disadvantages of comparatively poor surface hardness and deprived resistance against wear of Ti–6Al–4V alloy, the protective NiTi coatings are fabricated at different processing parameters by laser‐directed energy deposition (LDED). This work presents a comprehensive study of deposition morphology, phase constituents, microstructural evolution, composition distribution, and mechanical properties of as‐fabricated NiTi deposition tracks. The relationship among processing parameters and deposition morphology, phase constituents, and mechanical properties is established. The microstructural evolution mechanism and the composition distribution on the cross section of deposition tracks are revealed. Results show that the deposition tracks are successfully formed under all laser processing parameters, and the dilution ratio increases with the increase in laser power and scanning speed. The deposition tracks consist of NiTi2, NiTi, and α–Ti. According to the microstructural analysis, planar crystals are formed between the substrate and the deposition tracks, and columnar and equiaxed dendrites are found in the deposition tracks. The average microhardness increases continuously with the increase in laser power. The deposition track prepared at laser power of 1400 W has the highest average microhardness of 732.45 HV0.2. The deposition track at this laser power exhibits excellent wear properties, with a wear rate of 2.25 × 10−6 mm3 Nm−1.

Solid-State Additive Deposition of AA7075 on AZ31B Substrate: Heat Treatment to Improve the Corrosion Fatigue Resistance

The influence of heat treatment on the coating microstructure, nanomechanical, and corrosion fatigue properties of solid-state deposition of AA7075 aluminum alloy on AZ31B cast Mg alloy is studied in detail. Transmission electron microscopy (TEM) microstructural analysis shows columnar grain at the interface of AA7075/AZ31B. Electron backscatter diffraction (EBSD) observation discovered elongated grains with a high fraction of deformed grain boundaries as-deposited and heat-treated at 200 °C conditions. In contrast, the annealed samples show recrystallized grains with increasing temperatures from 200 °C to 400 °C. The residual stress of the coating at the surface and subsurface measured by X-ray diffraction shows −55 MPa and −122 MPa, respectively, which transferred to tensile with increasing the annealing temperature up to 400 °C. Annealing treatment of the AA7075 coating considerably improved the nanomechanical properties and corrosion fatigue resistance. With increasing the annealing temperature from 200 °C to 400 °C, the hardness of the coating decreased, while the modulus increased significantly. The analysis of fatigue fracture surfaces revealed that corrosive solution entered through the cracks and accelerated the crack propagation, lowering the fatigue life. However, the presence of recrystallized grains improved the corrosion fatigue resistance.

Effect of post-treatment on local mechanical properties of additively manufactured impellers made of maraging steel

PurposeThis study aims to investigate the effect of the wall thickness, deposition orientation and two different post-processing methods on the local mechanical properties and microstructure of additively manufactured parts made of maraging steel. In order to examine the local properties of the build, miniaturized testing specimens were employed. Before application of small-sized specimens, their performance was verified.Design/methodology/approachThe investigation was composed of two stages. As first, the part thickness, specimen size and orientation were studied on a laser-powder bed fusion (L-PBF) platform with deposited walls of various thicknesses made of maraging steel. Subsequently, the influence of different heat-treatment methods was investigated on the final product, i.e. impellers. The miniaturized and standard tensile tests were performed to investigate the local mechanical properties. The porosity, microstructures and fracture surfaces were analysed by X-ray-computed tomography, X-ray diffraction and scanning electron microscopy with electron backscatter diffraction.FindingsThe results revealed good agreement between the values provided by miniaturized and standard specimens. The thinnest parts produced had the largest pores and the highest scatter of elongation values. In these cases, also the sub-contour porosity was observed. Part thickness affected pores’ size and results repeatability but not total porosity. The two-step heat-treatment (solutionizing and age-hardening) exhibited the highest yield and ultimate tensile strength.Practical implicationsThe microstructure and local mechanical properties were studied on L-PBF platform with deposited walls of various thicknesses. Subsequently, a detailed analysis was conducted on real components (impellers) made of maraging steel, commonly used in tooling, automotive and aerospace industries.Originality/valueThe broadly understood quality of manufactured parts is crucial for their reliable and long-lasting operation. The findings presented in the manuscript allow the readers better understanding of the connection between deposition parameters, post-processing, microstructure and mechanical performance of additive manufacturing-processed parts.

Effects of ultrasonic vibration on microstructures and thermal properties of nickel-titanium shape memory alloy fabricated by directed energy deposition

Directed energy deposition (DED) has been previously utilized to fabricate nickel-titanium alloys; however, the inhomogeneity of microstructures and the formation of precipitates are still two major problems encountered in current DED processes. In this study, an ultrasonic vibration-assisted strategy is proposed and integrated into a DED process. The influences of ultrasonic power on deposition area, microstructures, and thermal behaviors of fabricated NiTi alloys are investigated. The results show that ultrasonic vibration can effectively improve deposition area and ameliorate the shape memory effect. The reported ultrasonic vibration-assisted strategy is expected to reduce the microstructure heterogeneity and secondary phase formation in nickel-titanium alloy fabrication.