Spray Deposition Process Research Articles

Multi-parameter coupled optimization of Al6061 coating porosity based on the response surface method

The objective of this study is to study the multi-particle deposition process of cold spray through numerical simulation methods and to use multi-factor coupling to optimize the porosity of Al6061 coating to more accurately characterize the real cold spray deposition process. This study aimed to predict and optimize the porosity of Al6061 coatings using numerical simulation methods. The tasks to be solved are: to nest the multi-particle model established by the Python script in the CEL deposition model to simulate the cold spray deposition process. A multi-parameter function with particle temperature, substrate temperature, and particle velocity as independent variables and Al6061 coating porosity as dependent variables was established. The response surface analysis method was used to predict the optimal spraying parameters and coating porosity of Al6061 coating. The methods used are as follows: optimize the porosity of the coating through multi-factor coupling through response surface analysis; use a multi-particle model established through a Python script to be nested in the CEL deposition model to simulate the deposition process of cold-sprayed Al6061 multi-particles. To characterize the coating porosity more accurately, the average value of multiple groups of samples was taken as the final coating porosity value. Conclusions. the porosity value of Al6061 coating obtained by the prediction model is 1.969%; Under the influence of multi-factor coupling, particle velocity has the greatest impact on the porosity of the Al6061 coating, and the substrate temperature has the least impact. Optimum spraying parameters: particle temperature 649.692K, substrate temperature 536.437K, and particle velocity 672.385m/s. Under the optimal spraying parameters, the porosity value of the Al6061 coating is 1.91875%; The error between the predicted value and the actual value obtained by numerical simulation is only 2.55%.

Investigating electrical properties and crystal growth in NiO thin films by spray pyrolysis and electrostatic spray deposition

The control of the electrical properties and the growth mechanism of the NiO films were investigated by Li addition using the spray pyrolysis method. In addition, to enhance the uniformity and flatness of the NiO films, the electric field applied spray pyrolysis named electrostatic spray deposition (ESD) process was applied. Experimental results suggest that a certain amount of Li acts as an interstitial on the Ni sites in the NiO film and enhances crystal growth. Moreover, excessive Li additions resulted in Li segregation into NiO crystal defects, whereas the resistivity decreases and the promotion of crystal growth was not inhibited regardless of the presence of Li on the NiO film up to a Li concentration of 10 at.%. Furthermore, ESD was confirmed to deposit highly flat NiO films. These results represent the initial step toward the practical application of visible-light-transparent devices using spray deposition.

Investigating the Structure and Performance of Electrodes Made by Dry and Wet Slurry Processes

Performance, cost, and safety are vital factors in producing and handling lithium-ion batteries. Using a dry process reduces the cost and environmental impact of producing large-scale lithium-ion battery electrodes significantly as solvents are eliminated. Thus, in this study, solvent-free dry electrostatic spray deposition (ESD) and conventional slurry processes were compared to uncover the influence of the manufacturing process on thick LiNi0.8Mn0.1Co0.1O2 (NMC 811) positive electrodes. More pressure during calendering was found necessary for the dry-made (dry) electrodes to have the same porosity, leading to more cracks within the NMC particles and better adhesion. At slower discharge rates, below 2 C, the dry electrodes exhibited a higher specific capacity or about the same capability than that of the slurry-made ones. At higher discharge rates, greater than 2 C, both types of electrodes have poor rate performance, though the slurry-made (slurry) electrodes had a slightly higher capacity. Despite more calendering-induced cracks in the dry electrodes, both electrodes had comparable long-term cycling behavior when tested in full cells with graphite-negative electrodes. This study shows the viability of using the dry-powder ESD process for manufacturing thick electrodes with high active material content, meeting the need for high energy demand.

Preferential Corrosion in Cold Sprayed Cu Induced by Oxide Inclusions

Cold spray (CS) deposition is a solid-state deposition technique that finds applications in additive manufacturing, coating, and repairing damaged components. During the cold spray deposition process, feedstock particles are accelerated by compressed gas and impinged onto the substrate at high velocity. Bonding between particles and the surface being coated is established by the high kinetic energy released during collision rather than by added thermal energy. As the particles remain in the solid state during spraying, oxidation is minimized. Despite the partial removal of the native air-formed oxides by the jetting effect, residual oxide debris often remains along the particle boundaries within the sprayed objects as inclusions [1]. The oxide inclusions have attracted attention concerning their influence on the inter-particle bonding strength in the deposit [2]. However, little is known about whether they affect the material’s corrosion behavior.In this work, we report a preferential corrosion phenomenon observed in a CS Cu-diluted HNO3 system that is caused by the remaining oxide inclusions. A mechanism that integrates Cu-NO3 – catalytic corrosion cycles with confined geometry resulting from the dissolution of the oxide inclusions is proposed. Furthermore, we find that this corrosion phenomenon may be mitigated through microstructure engineering. Annealing the CS Cu at 600 °C consolidated the oxide inclusions with their distribution changed from continuous thin films to isolated spherical particles [3]. The propagation of the preferential corrosion is hence interrupted by the lack of interconnected pathways. Counterintuitively, Cl– can function as an inhibitor for this preferential corrosion. Preferential corrosion did not initiate when 1 mM Cl– was initially present in the solution and slowed down when Cl– was added after the preferential corrosion occurred. Reference [1] S. Yin, X. Wang, W. Li, H. Liao, H. Jie, Deformation behavior of the oxide film on the surface of cold sprayed powder particle, Applied Surface Science, 259 (2012) 294-300.[2] Y. Ichikawa, R. Tokoro, M. Tanno, K. Ogawa, Elucidation of cold-spray deposition mechanism by auger electron spectroscopic evaluation of bonding interface oxide film, Acta Materialia, 164 (2019) 39-49.[3] J. Tam, B. Yu, W. Li, D. Poirier, J.-G. Legoux, J.D. Giallonardo, J. Howe, U. Erb, The effect of annealing on trapped copper oxides in particle-particle interfaces of cold-sprayed Cu coatings, Scripta Materialia, 208 (2022) 114333.

Electrostatic Spray Deposition of Al-Doped ZnO Thin Films for Acetone Gas Detection

In this study, pure ZnO and Al-doped ZnO(AZO) thin films were coated onto a SiO2 wafer using the electrostatic spray deposition (ESD) process for acetone gas detection under laboratory conditions. Voltage levels were varied to determine the optimal conditions for producing thin films with the highest uniformity. The results indicate that the optimal coating voltage for achieving the highest uniformity of the coated films is 2.9 kV for ZnO and 2.6 kV for AZO. The thin films were produced under these optimal ESD conditions by adjusting the coating time, and gas sensors were fabricated by printing electrodes using a reverse offset process on top of the thin films. Analysis of the sensing response revealed that the AZO-coated gas sensor with a 200 s deposition exhibited the best acetone-sensing ability at 300 °C, with a maximum response of 13.41 at 10 ppm. Furthermore, the fabricated gas sensors effectively detected acetone gas even at a low concentration of 2 ppm, demonstrating high selectivity in comparison to other gases.

A hybrid computational approach for modeling cold spray deposition

Cold spray (CS) is a cold-state technology that uses high-velocity supersonic gas flow to propel and deposit powder particles onto a substrate surface. The design and optimization of the cold spray deposition process were recently achieved via the experimental trial-and-error approach, which is laborious and costly. The present study presents a computationally efficient hybrid method for simulating cold spray coating deposition, applied explicitly to Ni coating used for wear applications. The model effectively synergizes meshless and meshed computational schemes in predicting the thermo-mechanical deformation of the impacting Ni particles and SS304 steel substrate. During the simulations, the point cloud (PC) of deformed particle domains is converted into a high-quality finite element (FE) mesh with novel PC processing algorithms. The simulations are carried out for various particle characteristics and spraying conditions. The numerical predictions are validated by comparing them with other numerical schemes and previous experimental studies. The main results indicate that the kinetic energy and morphology of the impacting Ni particles strongly influence plastic deformation and temperature rise in the substrate and predeposited coating particles. Plastic deformation is more prominent at the particle edges and mating material interfaces. At the same time, the temperature rise does not reach the melting point but can allow for recrystallization near highly localized regions of the coating microstructure, even at lower deposition rates. Compressive residual stresses are also observed across the coating and substrate layers, with a non-uniform and nonlinear residual stress field due to complex interactions among neighboring particles. The study aims to provide a robust numerical framework for designing and optimizing cold spray deposition parameters for industrial coatings, bridging the knowledge gap and enabling efficient and cost-effective simulations for process optimization.

Mechanical milling/alloying, characterization and phase formation prediction of Al0.1–0.5(Mn)CoCrCuFeNi-HEA powder feedstocks for cold spray deposition processing

In the present work the synthesis of multicomponent nanocrystalline Al0.1- 0.5(Mn)CoCrFeNi HEA powder feedstocks by mechanical alloying (MA) through high energy ball milling to produce HEA coatings with cold spraying were studied. Pure (>99.5) elemental powders of Al (Mn), Co, Cr, Cu, Fe & Ni were mixed in predetermined ratios and mechanically alloyed under Ar gas in a Planetary Ball Mill. MA HEA powder feedstocks were characterized by optical microscopy, SEM+EDAX, XRD & XPS to determine powder particle size, shape & distribution, particle surface condition, chemical composition, crystal & phase structures & microstructures. MA-processed Al-HEA powder feedstocks exhibited tri-modal particle size distribution (PSD) while Mn-HEA had four distinct PSD modes. Fine size fraction of the MA- HEA powders contained A2/B2 (BCC) harder phases with lattice parameters of 2.8831 and .2.8690 Å, respectively and coarse size fraction contained (ductile) softer A1 phase/Cu-rich regions combined (FCC) having a lattice parameter of 3.6181 Å. The ratio of the phases varied depending on the Al and Mn contents in the powder. For higher aluminium contents, there was more disordered A2/B2 phases and less disordered A1 phase in Al0.1–0.5 HEA powder feedstocks. A1 phase contained Fe, Cr, Co and Ni; A2 phase contained Fe, Cr; and B2 phase contained Al, Ni elements in Al0.1–0.5 HEA powder feedstocks. There were passive surface oxide films on the rough surfaces of MA HEA powder feedstocks consisting of a main mixture of surface oxides such as Al2O3, MnO, Cr2O3, Mn2O3, and minor oxides such as CuO, Fe2O3, NiO, Fe3O4, and a few CoCr2O4 spinel oxide. Dual FCC-dual BCC phase prediction of thermodynamic stable phase formation criteria reported in the literature on MA-HEA powder feedstocks were consistent with the experimental results of the present study.

An experimental investigation on metallurgical and corrosion behavior of atmospheric plasma sprayed Stellite 6 powder on AISI 304 stainless steel

An experimental investigation was undertaken to study the Cobalt-based Stellite 6, powder deposited on SS 304 stainless steel substrate without any intermittent layer using an atmospheric plasma spray deposition process by varying the thickness of coating in the range of 74 µm, 128 µm, and 215 µm. The effect of coating thickness on metallurgical properties and corrosion resistance behavior was investigated. Optical microscopy, Scanning Electron Microscopy (SEM), and Energy Dispersive X-ray Spectroscopy (EDS) were employed to study the morphology of Stellite 6 coating. X-Ray Diffraction was used for structural analysis and to identify the phase formation. It was observed that the sample with 128 µm coating thickness provides the best result concerning microhardness and microstructure characteristics whereas the sample with 215 µm coating thickness provides the best corrosion resistance property. The reasons for the deviation were investigated and the factors responsible for the deviation were assigned in this investigation.

Area-dependent performance variation of ultrasonic spray-coated organic solar cells

Here, a comparative study has been performed to understand the scalability of as developed ultrasonic spray deposition process for large-area organic solar cell fabrication. It was observed that the performance of the devices reduces with increasing active area dimensions. The short circuit current density and power conversion efficiency got decreased by more than 70% on increasing the device area from 0.04 to 1.5 cm2. In the case of small-area devices, the low electrical resistance owing to fewer droplet boundaries and negligible pinholes of the spray-coated film leads to better device performance. Whereas, upon scaling up the device area, the non-uniformity of the spray-coated film starts dominating and is found to be responsible for the reduction in overall device performance. The non-homogeneous film morphology in the case of larger-area devices greatly affects the charge generation, as it decreased from 4.77 × 1021 to 1.92 × 1021 cm−3 s−1 for large-area devices compared to small-area ones. The results suggest that the spray-deposited films greatly suffer from the limitation of droplet boundaries and pin-holes, which need to be addressed further with post-deposition treatments, in order to fabricate commercially viable large-area devices.

Cold spray manufacturing of oxide-dispersion strengthened (ODS) steels using gas-atomized and ball-milled 14YWT powders

The cold spray deposition process has been investigated for the manufacture of 14YWT oxide-dispersion strengthened (ODS) steel, a nanostructured ferritic alloy (NFA), using gas-atomized and ball-milled feedstock powders. Cold spraying of the gas-atomized powder resulted in a thick dense deposit, but annealing them above 900 °C induced grain growth and heterogeneous precipitation of nanoparticles, thus resulting in lower hardness (∼ 170 HV) compared to 14YWT ODS steel manufactured by the conventional method. The ball-milled powder (Fe-14Cr-3W-0.4Ti-0.2Y-0.125O) was cryomilled in liquid N2 to achieve small particle sizes followed by annealing in a H2/Ar environment at 1000 °C and 1100 °C to reduce the hardness from ∼ 8 GPa to ∼ 5 GPa. Both smaller particle sizes and lower hardness of annealed powders made them amenable to the cold spray deposition process, resulting in thick and dense deposits, while retaining the favorable fully solutionized microstructure of the ball-milled powders. The microstructure of the as-deposited ODS exhibited very fine grain sizes (50–250 nm) with a uniform dispersion of Y-Ti-O nanoprecipitates in the ferritic steel matrix. The hardness values of the cold spray deposits using the powders annealed at 1000 °C and 1100 °C was 770 HV and 496 HV, respectively. Post-heat treatment of the as-deposited material up to 1100 °C showed a high-density microstructure with uniformly dispersed nanoscale oxide particles. The hardness of the annealed deposits up to 1000 °C had a notably higher hardness than bulk 14YWT ODS steel manufactured by conventional methods. The study demonstrates that cold spray deposition of the microstructurally-tailored feedstock powders can be used to successfully manufacture ODS steel with microstructure and properties comparable to those produced by the conventional methods, while providing for an attractive option for the more rapid and cost-effective manufacturing of ODS steel cladding tubes.

Spray Pyrolyzed Praseodymium Doped SnO2 Thin Film with Fast Response to LPG: Analysis Based on Microstructural Features

Praseodymium (Pr) doped (0.1 to 6 wt. %) nanostructured SnO2 thin films are prepared via nebulizer assisted spray deposition process at a deposition temperature of 320 °C. The analyses show that the films grow in (110), (301) and (310) preferred orientations. The fabricated sensing films are exposed to LPG at 500 ppm concentration and at different operating temperatures. In 500 ppm of LPG, at an operating temperature of 350 °C, a commendable sensor response of 99 % with fast response time of 9 s and recovery time of 11 s is shown by 1wt.% Pr doped film, which is appreciable compared to pristine SnO2 film. The sensor response reduces at lower operating temperatures. Microstructural investigations justify the gas sensing performance of 1 wt.% Pr doped SnO2 thin film. Raman and photoluminescence studies give an insight into oxygen vacancies and trapped states that have a crucial influence on gas sensing.

Understanding the Effects of the Mixing Processes on the Performance of NMC-LMO Blend Electrodes Made By a Dry Electrostatic Spray Deposition Process

Improving the manufacturing process of making lithium-ion batteries (LIBs) is a key to further decreasing the cost and expanding the market of LIBs for many applications, especially for electric vehicles. Since electric vehicles require durable, sustainable, and cost-effective battery systems for their continued enlargement, advanced manufacturing processes of LIBs need to be investigated. The conventional wet slurry operation for LIB electrode manufacturing imposes several limitations on cost and performance mostly due to solvent usage. The drying process for the evaporation and recovery of organic solvent requires the use of unwanted solvents that do not contribute to the final product, thus consuming energy. If solvent evaporation is not controlled well, issues such as binder migration, segregation, and cracking of the electrode can occur, affecting the performance of the battery. Therefore, using a solventless dry process for electrode manufacturing has the potential to reduce the cost and environmental impact by eliminating solvent usage.In this work, electrostatic spray deposition (ESD) without the use of a solvent is investigated for manufacturing thick NMC811/LMO electrodes. Comparing two different dry powder mixing methods, we showed that dry powder mixing prior to ESD has a significant effect on the electrode microstructure and, consequently, its performance. Electrodes made by ball mill mixing retained better discharge capacity, which was attributed to the low charge transfer resistance and improved ionic conductivity due to porous conductive pathways formed between and on the active material particles. High speed mixing, on the other hand, caused dense layers of binder and conductive agent agglomerates, limiting the contact area of the electrolyte with active materials and increasing the resistance.

Resistance spot welding of printed interlayers to join Al–Fe sheets

ABSTRACT Cold spray and laser powder bed fusion deposition processes were explored and found to significantly increase the peak force and fracture energy of the press hardened boron steel–aluminium joint. The use of 250 µm thick 316L metallic interlayers was resistance spot welded to an AlSi-coated press hardened steel and 6022-T4 aluminium alloy. Moreover, aluminium penetration within the deposited 316L promoted a mechanical locking effect which was assessed by increasing the hatch spacing in the laser powder bed fusion process from 100 to 200 µm.

Tuning the shell structure deformation of APS thermal barrier coatings: A molecular dynamics study

A key parameter for the performance of ceramic topcoats in a thermal barrier coating is the porosity, which is sensitive to many growing conditions. In the present work, molecular dynamics simulations are performed to investigate the microscopic mechanism for the dependence of the porosity on several experimental conditions in the atmospheric plasma spraying deposition process, including temperature, substrate roughness, and the thickness-to-radius ratio of the yttrium-stabilized zirconia shell. These factors can significantly modify the porosity through changing the buckling mode of the yttrium-stabilized zirconia shell. Our findings provide some microscopic mechanisms for improving the deposition quality of the atmospheric plasma spraying thermal barrier coatings.

Additional hindrances to metallurgical bonding from impurities during microparticle impact

Successful cold spray processing requires the formation of metallurgical bonds at the interface between particle impact sites and the substrate. While surface contamination on either the particle or substrate can interfere with metallurgical bonding, the details of particle/substrate interface chemistry are usually obscured or lost during the nanoseconds-long particle impact process. To provide a direct, detailed account of particle-substrate interfacial chemistry, we perform post-mortem scanning transmission electron microscopy and spectroscopy of impact sites of single copper microparticles, launched with a laser-induced particle impact tester, on a copper substrate. In addition to native oxides, we find that amorphous carbon and spherical copper oxide dispersoids are also present near/at the interface. Further, these features are found to influence metallurgical bonding. These results offer additional considerations for optimizing the quality of the cold spray deposition process.

Evaporation-controlled spray deposition process achieving ultrasmooth photoactive layer for efficient organic solar cells

Spin-coating is a deposition method widely used in lab-scale experiments with organic solar cells. This method is, however, not adequate for large-area coatings since it produces excessive material waste. For this reason, a growing community of researchers is investigating alternative scalable deposition techniques to deposit photovoltaic devices from polymer solution. In this study, we introduce a facile spray coating method to fabricate a smooth and uniform bulk heterojunction morphology of organic photovoltaic devices based on a mixture of conjugated polymer and fullerene. The high surface roughness of spray-coated films is significantly reduced by controlling the spray deposition parameters closely related to the solvent evaporation rate. The drying kinetics of solvents affect surface roughness of the spray-deposited film and polymer crystallinity, correlating with the photodiode characteristics, such as the leakage current and rectifying ratio. This spray coating method is optimized for device fabrication to achieve a high-power conversion efficiency (PCE) of 3.55% for P3HT and a PCE of 7.53% when applied to PTB7-Th, a low band-gap conjugated polymer.

Influence of the deposition parameters on the tribological behavior of cold gas sprayed FeMnCrSi alloy coatings

Cold Spray deposition process may be an alternative for the High-Velocity Oxy-Fuel (HVOF), providing high kinetic energy without particles oxidation. In this work, an FeMnCrSi alloy was deposited onto carbon steel substrate by Cold Gas Spray (CGS) process varying spraying parameters (working gas, its pressure and temperature). Cavitation resistance was evaluated by ultrasonic cavitation testing, and the sliding wear resistance was studied by ball on disk testing, with intent to understand the behavior of this coating when exposed to sliding wear condition. FeMnCrSi sprayed using N2 working gas at 1000 °C showed higher hardness, elastic modulus, cavitation resistance, and sliding wear resistance than FeMnCrSi deposited with 900 and 1100 °C. The samples deposited with N2 at 1000 °C and He at 600 °C showed higher compressive residual stress and flatenning ratio also. The tests were performed for CGS sprayed 316 L stainless steel, which is used as a benchmark material.

Estimation of coating thickness in electrostatic spray deposition by machine learning and response surface methodology

To improve the quality and productivity of the process or system before resorting to expensive and laborious experimental tests, it is essential to model and predict the system performance concerning its operational parameters. Predictive modeling and parameter optimization through machine learning techniques has been the most advantageous process and are the best alternative to the conventional statistical tools. In this work, carbide cutting tool inserts were coated with molybdenum disulfide (MoS2) solid lubricant utilizing the electrostatic spray deposition (ESD) process. The optimum artificial neural network (ANN) model with 3-6-6-1 architecture includes 0.6 momentum term and 0.3 learning rate with attained mean squared error (MSE), absolute error in prediction (AEP) of trained and test data are 0.000334, 0.197, and 0.543, respectively. The support vector machine (SVM) hyperplane parameters are optimized using the Bayesian optimization technique, and after 90 evaluations, the model with the least error is used for predicting ESD coating thickness. The coating thickness predictions from ANN and SVM models were related to the response surface methodology (RSM) model predictions. From the results presented, the correlation coefficient (R-value) between experimental results and model predictions for ANN and SVM are 0.979 and 0.991, respectively, whereas, for RSM, it is 0.919. In addition, a genetic algorithm (GA) has been employed to establish the optimum conditions for the ESD deposition parameters. The presented SVM and GA method would support rapid and precise estimate and optimization of coating thickness in the ESD process.

Large-area and low-cost Cu–Cu bonding with cold spray deposition, oxidation, and reduction processes under low-temperature conditions

Large-area and low-cost Cu–Cu bonding with cold spray deposition, oxidation, and reduction processes under low-temperature conditions

A comparative study of tensile properties of eutectic Al-Si / ZrO2 composites fabricated by spray forming and stir casting methods

ABSTRACT The study aims to investigate the microstructural and mechanical properties of Al-12.5%Si matrix composites reinforced with ZrO2 were fabricated by spray forming method and stir casting (SC) technique by varying reinforcement of 2%, 6% and 10 wt.% ZrO2 powder (size 25 μm).The spray-formed (SD) composites were subjected to hot (400°C) isostatic pressing to reduce the porosity. The microstructure of spray-formed and SC composites were examined using optical and SEM/ EDS. The microstructure of the spray-formed composites showed uniform distribution of fine Si, eutectic phase and ZrO2 particles in the equiaxed Al-matrix. In contrast, SC composites consist of a coarse Si, needle like eutectic phase and clustering of reinforcement particles at grain junctions as a continuous network along the grain boundaries. The hardness, ultimate tensile strength of both spray-formed and SC composites improved as the ZrO2 content increased, while yield strength decreased. Spray-formed composites showed better mechanical properties. This was attributed to uniform distribution fine of Si particles, reinforced particles, equiaxed matrix induced during spray deposition process. Tensile fracture surface of spray-formed composites possess ductile and cleavage fractures. SC composites showed intragranular cracks in coarse Si particles and increase in micro-cracks with increasing reinforcement.