Powder Spray Research Articles

Effect of efficient structural tuning on the microstructure, corrosion resistance, and wear performance of AlCoCrFeNi/AT13 composite coatings

This study developed a rapid structure control technique for AlCoCrFeNi/AT13 (Al₂O₃–13 % TiO₂) composite coatings using plasma spraying and dual powder feeding. Four coatings were fabricated: pure HEA, HEA-D (dispersed), HEA-S1 (multilayer with outer HEA), and HEA-S2 (multilayer with outer AT13). The introduction of AT13 altered the internal stress distribution and enhanced corrosion resistance by lowering the electrochemical reaction rate. In layered coatings (HEA-S1, HEA-S2), the AT13 interlayer barrier reduced corrosion tendency. Additionally, pure HEA coatings exhibited adhesive wear. While HEA-D coatings experienced abrasive wear as AT13 particles improved plastic deformation and interface shearing. HEA-S1 reduced strain and wear via an internal AT13 layer. HEA-S2 achieved superior abrasion resistance through an outer AT13 layer, exhibiting typical abrasive wear mechanisms.

Effect of shell composition on watertightness and mechanical performance of cement-based capsules used as self-healing additives of cement

The aim of this work is the development of cementitious macro-capsules for self-healing cement and concrete materials. Emphasis is placed on shell properties, including size, thickness, strength, and volume to active component ratio. This enhancement is aimed at protecting the healing agent and ensuring adequate reactivity upon crack formation, surpassing survivability considerations. To this direction, core/shell particles have been produced following the pan-coating method, while different types and concentrations of setting acceleration solutions for the shell stabilization were studied. The formation of core-shell capsules encompasses the formation a spherical core through agglomeration, followed by simultaneous spraying of cement powder and a setting acceleration solution for the shell formation, under continuous rotation. The microstructural characteristics of the shell were studied through scanning electron microscopy (SEM), while the reactivity of the protected core (reactive agent) inside the hardened mortar mixtures was evaluated using thermogravimetric analysis (TGA). Moreover, the crushing load of the capsules under compression and their survivability during mixing process were examined and interpreted in relation to their diameter, circularity, and shell thickness.The results revealed the ability of the encapsulation methodology proposed to tailor the shell properties and modify the capsule properties so as satisfy the requirements of different applications. The use of setting accelerators during shell formation proved essential for enhancing the density and the strength of the shell layer. As a consequence, this leads to macro-scale capsules with elevated survivability rate and core reactivity.

Formation of coatings of the FeTi‒SiC system during thermal spraying of powder produced by the method of mechanochemical synthesis

Formation of coatings of the FeTi‒SiC system during thermal spraying of powder produced by the method of mechanochemical synthesis

Electrostatic spraying of zinc carbonate hydroxide-infused ethylene-tetrafluoroethylene powders: A thermally-induced, VOC-free antibacterial superhydrophobic coating

This study introduces an environmentally friendly method to create a superhydrophobic antibacterial coating using electrostatic powder spraying. The process utilizes ethylene-tetrafluoroethylene copolymer (ETFE) and zinc carbonate hydroxide (ZCH) powders and no organic solvent was used. The resulting coating takes advantage of ETFE's hydrophobic properties and the microstructure generated from ZCH's thermal decomposition, producing a micrometer-scale porous structure with a water contact angle of 165°. It demonstrates strong adhesion to substrates, fulfilling grade 0 standards as per GB/T 9286–2021 / ISO 2409:2020. Following 3 cycles of the falling-sand test, as outlined by ISO/TS 10689:2023, the contact angle impressively remains above 150°, underscoring its extraordinary resistance in contrast to coatings described in literature that typically endure just about 1 cycle. Even after 10 cycles of high-speed water jet impacts following ISO/TS 10689:2023, it maintains a water contact angle of 145°, equivalent to resisting ten years of continuous rainfall based on ISO/TS 10689:2023. The coating's antibacterial effectiveness, stemming from its superhydrophobic characteristics and the antibacterial properties of ZnO produced by ZCH decomposition, achieves inhibition rates of 99.6 % and 99.8 % against E. coli (ATCC 25922) and S. aureus (ATCC 6538) respectively, highlighting its significant potential for practical applications.

ОЦЕНКА ВЛИЯНИЯ РЕЖИМОВ ШЛИФОВАНИЯ НА ШЕРОХОВАТОСТЬ ПЛАЗМЕННЫХ ПОКРЫТИЙ

The equipment for laboratory tests during grinding of plasma coatings is presented. The results of the study of the influence of the modes of mechanical treatment with an abrasive tool on the quality of the surface of plasma coatings are presented. Three materials were applied to the surfaces - based on iron, nickel and self-fluxing powder for plasma spraying, with their subsequent grinding and study of the surface quality.

Microstructure and properties of plasma sprayed NbC-Al2O3 composite coatings

Niobium carbide has received widespread attention due to its high melting point, high strength, high chemical stability and high wear resistance, but the current preparation of niobium carbide coatings using plasma spraying technology suffers from low deposition efficiency, poor fusibility of the composite powders, high porosity, and high defects in the coating microstructure. Therefore, the microstructure and properties of NbC-Al2O3 composite coatings prepared by plasma spraying NbC-Al2O3-SiC composite powder and reactive plasma spraying Nb2O5-SiC-Al composite powder were comparatively investigated in this paper. The reaction mechanism of Nb2O5-SiC-Al composite powder during plasma spraying as well as the mechanism of the formation of coatings were analyzed in detail. The results showed that compared with the ex-situ NbC-Al2O3-SiC coating fabricated by plasma spraying, the in-situ Nb2O5-SiC-Al composite coating prepared by reactive plasma spraying had an obvious layer structure, low porosity (5.8%), high hardness (1141 HV0.1), high toughness (22.94 J/m2), and good scratch resistance properties.

Research into the Structure and Adhesion of WCCoCr Coatings Plasma-Sprayed onto Castings of AlSi Alloy Plates

The article presents structural investigations and mechanical properties of hard coatings deposited by spraying WCCoCr powder in an argon-hydrogen plasma jet onto the surfaces of AlSi10Mg alloy casting plates. Two variants (A and B) of processing parameters of the powder spraying process onto the surface of silumin plates were applied, resulting in different coating thickness. The coating applied according to variant A was done with 12 passes, and its thickness was approximately 150 μm. The coating applied according to variant B was done with 20 passes, and its thickness was about 320 μm. The microstructures of these coatings are similar, consisting of wavy, alternately deposited phases of solid solutions with varying concentrations of elements, and fine spherical phases, irregularly dispersed carbides. A qualitative analysis of the distribution of microstructure components was performed based on surface mapping. Precipitates differing in their degree of grayness and shape were identified based on microanalysis of their chemical composition. The porosity assessment of coatings performed in five randomly selected areas amounts to an average of 9%. The applied coatings exhibit good adhesion to the substrate, as evidenced by the absence of delamination during scratching tests using a diamond Rockwell indenter loaded with a force of 10 N. The coating hardness averaged 1180HV0.2. The test results indicate the high quality of the WCCoCr coatings, regardless of their thickness.

Effect of airflow velocity in vessel-pipelines on dust explosion during pneumatic conveying

In order to investigate the flame propagation and pressure characteristics of dust particles during airflow transportation, a dust explosion experimental apparatus simulating dust handling processes was designed. The system is supplied with a stable airflow by a high-pressure fan, capable of continuously transferring dust from the vessel to the pipeline at a controllable speed. Dust explosion experiments were meticulously executed by applying 1 kJ of ignition energy to the transported dust particles at airflow velocities of 5, 10, and 15 m/s. This study examines the effects of airflow velocity, pipe diameter, and ignition position on explosion characteristics and delves into the mechanisms of these effects through a detailed analysis of experimental results. For the maximum explosion pressure, an increase in airflow velocity causes the maximum explosion pressure to rise. As the pipe diameter increases, the maximum explosion pressure first rises and then falls. The maximum explosion pressure occurs in the case of bottom ignition. The range of maximum explosion pressure values is expected to provide a reference for explosion detection and explosion venting. For flame propagation, the flame undergoes five processes within the vessel, including ignition of dust particles, spherical flame development, flame stretching towards the mouth of the pipe, complete combustion of particles, and near exhaustion of particle combustion. The higher the airflow velocity and the larger the pipe diameter, the more pronounced the flame stretching and development towards the pipe opening become. Within the pipe, two distinct flame propagation behaviors were observed under conditions of high and low airflow velocities. Compared with the experimental results of high-pressure pneumatic powder spraying forming a dust cloud within a vessel-pipeline, this study measures the maximum explosion pressure at specific turbulence levels and establishes a quantitative relationship between airflow velocity and explosion characteristics. Utilizing this correlation can provide a reference for predicting industrial-grade dust explosion characteristics at different airflow velocity levels, thereby offering a more optimized design basis for the design and safety protection of industrial equipment.

Microstructure and wear resistance of cold sprayed CoCrFeNi HEA coatings: Influence of powder particle size and spraying temperature

This study focuses on the successful fabrication of three distinct types of CoCrFeNi high entropy alloy (HEA) coatings through cold spray (CS) technology, with an emphasis on analyzing the impact of varying crucial CS parameters (spraying temperature and the range of powder particle size), on the coating's microstructure and tribological properties. Contrasted with conventional thermal spraying techniques, lower operational temperature in CS safeguards the materials from undergoing oxidation or phase transitions that are typically induced by high-temperature conditions. Additionally, the high-velocity impact of particles onto the substrate within CS process triggers plastic deformation, resulting in the creation of coatings that are characterized by heightened hardness, and greater density. Such coatings exhibit significantly enhanced performance and durability. The cocktail effect observed in CoCrFeNi HEA is reflected in a suite of exceptional properties that markedly surpass those exhibited by traditional alloys. Chiefly, this phenomenon is manifested through the alloy's exceptionally high hardness and dense structure, positioning CoCrFeNi HEA as a promising candidate for applications in high-wear scenarios. Experimental outcomes indicate that when smaller powder particles and higher spraying temperatures are employed, the porosity of CSed CoCrFeNi HEA coatings was observed to decrease by nearly an order of magnitude, concomitant with a 22.46% enhancement in microhardness. This improvement in microhardness translates into a significant reduction of over 72% in the wear rate, underscoring the positive correlation between enhanced microstructural integrity and wear resistance properties. By meticulously tuning spraying temperature and powder particle size, the resulting microstructure can be rendered increasingly dense and refined.

In vitro evaluation of spray and freeze-dried bovine colostrum powder and their effects on the nutritional and functional properties

ABSTRACT Bovine colostrum is the initial milk produced after birth that contains high levels of immunoglobulins and antimicrobial peptides. This study examined the production of bovine colostrum powder using two methods including spray- and freeze-drying. Spray-drying involves quickly drying a liquid or slurry with hot gas, while freeze-drying is a low-temperature dehydration process that preserves the product by freezing it and at reduced pressure. The aim was to compare the effectiveness of spray-drying versus freeze-drying in producing colostrum powder, focusing on protein and defensive protein content. The freeze-drying sample contained higher levels of protein and defensive proteins (IgG and IgA) compared to spray-drying. The DPPH value was high in freeze-dried samples, while higher values of FRAP, TPC, and ABTS were found in spray-dried samples. Microbiological analysis indicated freeze drying generally yielding lower counts. Sensory evaluation suggested that spray-dried colostrum scored higher for flavor and aroma, while freeze-dried samples were preferred in appearance. Overall, the study underscored the distinction between spray=drying and freeze-drying in producing bovine colostrum powder, with implications for nutritional content and sensory attributes.

Cold Spray Technology and Its Application in the Manufacturing of Metal Matrix Composite Materials with Carbon-Based Reinforcements

Cold spray technology, as an emerging surface engineering technique, effectively prepares hard coatings by high-speed projection of powder materials onto substrates at relatively low temperatures. The principal advantage of this technology lies in its ability to rapidly deposit coatings without significantly altering the properties of the substrate or powder materials. Carbon-based materials, especially carbides and diamond, etc., are renowned for their exceptional hardness and thermal stability, which make them indispensable in industrial applications requiring materials with high wear resistance and durability at elevated temperatures. This review elucidates the fundamental principles of cold spray technology, the key components of the equipment, and the properties and applications of hard coatings. The equipment involved primarily includes spray guns, powder feeders, and gas heaters, while the properties of the coatings, such as mechanical strength, corrosion resistance, and tribological performance, are discussed in detail. Moreover, the application of this technology in preparing metal matrix composite (MMC) materials with carbon-based reinforcements, including tungsten carbide, boron carbide, titanium carbide, and diamond, are particularly emphasized, showcasing its potential to enhance the performance of tools and components. Finally, this article outlines the challenges and prospects faced by cold spray technology, highlighting the importance of material innovation and process optimization. This review provides researchers in the fields of materials science and engineering with a comprehensive perspective on the application of cold spray technology in MMC materials with carbon-based reinforcements to drive significant improvements in coating performance and broaden the scope of its industrial applications.

Fabrication of multi-reinforced powders for gas-dynamic spraying by powder metallurgy

Fabrication of multi-reinforced powders for gas-dynamic spraying by powder metallurgy

3D volume construction methodology for cold spray additive manufacturing

Cold spraying has proved as an attractive and rapidly developing solid-state material deposition process that allows for fast formation of high quality, large 3D volume objects. Low risks of undesirable heat effects lead to increased interest in cold spraying based rapid additive manufacturing. However, by continuous powder spraying and high-pressure gas operation, cold spray additive manufacturing in terms of shape building is sensitive to operating parameters and imposes high requirements on the control of process conditions and locally needed kinematics. Every step of the manufacturing process therefore needs to be meticulously conceived and planned, especially the toolpath planning and implementation. This is not only essential to meet basic performance requirements, but also needed for the desired geometric accuracy. To address these needs, this study presents a new implementation method for cold spray additive manufacturing to improve manufacturing accuracy and flexibility. The workflow and principles of the proposed method are explained and strategies are presented for building up various component types, including rotational geometries as well as freestanding parts. The developed algorithms for 3D applications can be well integrated into the cold spray additive manufacturing process for toolpath planning and path parameter determination. Reliable and accurate robot programs were developed to make the process easy to repeat and to follow. Toolpath planning and robot programming are supported and performed by applying virtual cells to simulate the automation process for the real scenario. Path parameter adjustment and kinematic optimization can then be conducted according to the feedback from the simulation result. Applied benchmarking tests prove acceptable shape accuracy and demonstrate that the current method can enhance the capabilities of cold spray additive manufacturing for near-net shape construction. This implies that careful planning and manufacturing strategies should enable overcoming the challenges associated with cold spray additive manufacturing.

Artificial neural network model for wear characteristic analysis of WC-10Co4Cr and Stellite 6 thermal spray coatings

In this paper, wear characteristic analysis of the thermal spray powders namely WC-10Co4Cr and Stellite 6 high velocity oxy-fuel (HVOF) coated on SS 316 L steel were studied. Artificial neural network (ANN) model predicts the accuracy by the coefficient of R= 0.99 and R2 = 0.98. The R2 of present ANN model was far better as compared to regression models Enbt (0.85), Coarse Tree (0.04), linear regression i.e. LR (0.37), and Enbag (0.19). Results show that uncoated SS 316 L steel was severely eroded, and wear occurred on the bare SS 316 L was about 7.5 ± 2.5 times higher as compared to WC-10Co4Cr coating, and 3.5 ± 1.5 times than Stellite 6 coating.

Design and experimental evaluation of a variable pesticide application control system for the air-assisted rubber tree powder sprayer.

In order to address the issues of uneven pesticide deposition and low pesticide utilization in rubber gardens caused by the traditional diffuse plant protection spraying method, this study focuses on the air-assisted powder sprayer and proposes a variable pesticide application control system. A variable pesticide application decision-making model integrating the leaf area index (LAI) was designed based on powdery mildew control standards and individual rubber tree information. According to the target powder spraying accuracy requirements, a control model of the air velocity adjustment device was established and a fuzzy proportional-integral-differential (PID) air velocity control system was developed. The simulation results indicate that the wind speed control system exhibits a maximum overshoot of 2.18% and an average response time of 1.48 s. The field experiment conducted in a rubber plantation revealed that when the air-assisted powder sprayer operates in the variable powder spraying mode, the average response time of the control system is 2.5 s. The control accuracy of each executive mechanism exceeded 95.9%. The deposition coefficient of variation (CV) at different canopy heights was relatively consistent, with values of 35.38%, 36.26% and 36.90%. In comparison to the quantitative mode, the variable mode showed a significant 20.03% increase in the effective utilization rate of sulfur powder. These research findings provide valuable technical support for the advancement of mechanized variable powder spraying equipment in rubber tree cultivation. © 2024 Society of Chemical Industry.

The Effect of the Size of SUS316L Flake Powder on the Characteristics of Metal Powder Filt ers with a Double-Layered Pore Structure Fabricated by the WPS Process

When fabricating a metal powder filter with a double-layered pore structure, which includes a microporous layer, by coating flake-shaped powder using the Wet Powder Spray (WPS) process, it is crucial to ensure that the coating is applied parallel to the surface of the metal powder filter. Failure to do so can result in a non-uniform pore structure, leading to a rapid decline in particle filtration efficiency. Therefore, it is necessary to improve the alignment of the coated flake-shaped powder on the filter surface. In this study, a metal powder filter with a double-layered pore structure was fabricated by applying a flake-shaped metal powder coating to a tube-shaped SUS316L powder filter using the WPS process. In order to improve the flake-shaped powder orientation of coating layer, the impact of the rolling process was investigated. The characteristics of the pores were analyzed based on the powder size and the rolling time. The microstructure of the fabricated metal powder filter was observed using an optical microscope, surface roughness, variations in thickness, and air permeability were analysed.

Building a Layer-Structured Aluminum/Graphene Composite with Significant Improvement in Electrical Conductivity.

Aluminum (Al) and its alloys are widely used in various fields due to their excellent physical properties. Although many efforts have been made to fabricate an Al-based composite, they usually results in a significant decrease in electrical conductivity. Herein, a special layer-structured Al/graphene (Gr)/Al composite was successfully designed and fabricated through a facile method using the ultrasonic spraying of graphene powder with alumina removal and a subsequent vacuum hot-pressing process. The as-obtained Al/Gr/Al composite presents a significantly enhanced electrical conductivity of 66% IACS, which is much higher than that of other reported Al-based composites, while it still maintains similar mechanical properties. This work provides a new strategy for the development of highly conductive Al-based composites, which would be very useful and important for practical applications.

Numerical Simulation and Experimental Study of Gas–Solid Two-Phase Spraying of Dry Powder Fire-Extinguishing System Based on Fire-Extinguishing Inspection Robot

In order to solve the problem where the traditional intelligent inspection robot only has a single inspection function, we studied the use of a dry powder (including an ultra-fine dry powder) as a fire-extinguishing medium for the first time. In fire-extinguishing robots, the spray pressure is difficult to control, and there are several other issues. For integrated inspection, an intelligent, nitrogen-driven fire-extinguishing robot using a dry powder in a pressure-controlled spray was developed. On this basis, in order to investigate nitrogen-driven dry powder particle spraying as a gas–solid two-phase mechanism, as well as the flow characteristics and the influence of relevant parameters on the spraying effect, a nitrogen-driven dry powder particle spraying system was established as part of a gas–solid two-phase computational fluid dynamics model. The flow field of the spraying system and the particle motion characteristics were analyzed to explore the micro-mechanisms of the influence of different driving pressures, pipe diameters, and nozzle configurations on the spraying of the dry powder. In order to investigate the macroscopic effect of dry powder spraying where the gas–solid two-phase micro-mechanisms could not be revealed, an experimental platform was set up, and the experiments verified the accuracy of the numerical simulation results. We also investigated the dry powder spraying effect under different driving pressures, pipe diameters, nozzle configurations, and loading ratios. Finally, an orthogonal test was designed based on the results of the single-factor experiments to find the best combination of parameters required to achieve the optimal spraying effect. The research results can provide a theoretical and technical reference for the design and development of nitrogen-driven dry powder spraying systems.

Investigating the Effects of CoMoCrSi Powder Composition and Particle Size, and Annealing Heat Treatment on Microstructure and Mechanical and Tribological Performance of HVOF Sprayed Coatings

AbstractAn investigation was conducted to analyze the mechanical properties, wear behavior, and microstructure of coatings formed by high-velocity oxygen fuel spraying of CoMoCrSi powders. The effects of varying Cr concentration and particle sizes before and after heat treatment at 900 °C for 4 h were studied comparatively. The increase in Cr and Mo elements in the expanse of Co increased the structure's hardness before and after the heat treatment. As this increase was 10% in as-sprayed conditions, annealing raised the increase to 30%. Splat boundaries were the most vulnerable constituents against forces, creating a significant disadvantage in terms of structural integrity and affecting the overall performance. After annealing, the boundary strengths experienced a remarkable four-fold increase and cracks and fractures reduced significantly. The susceptibility of splat boundaries had a detrimental effect on room temperature wear behavior, and increased boundary densities led to a marked reduction in wear performance. Heat treatment induced improvements significantly increased the room temperature wear performance. At elevated temperature, the formation of oxide layers composed of CoMoO4, Co3O4, MoO3, and Cr2O3 overcame the weaknesses of the as-sprayed coating, reducing both the friction coefficient and wear losses. A reduced Co ratio led to the formation of an oxide blend with a higher concentration of Mo and Cr oxides on the surface, further improving the coating's wear behavior. Graphical Abstract

Generation of a lignin-polyester coating for the corrosion protection of steel surfaces applied by atmospheric plasma spraying

The natural process of metal corrosion causes significant losses in a wide range of industries, requiring substantial efforts to contain its effects. An alternative approach to corrosion protection is the use of renewable organic coating materials. This research proposes the use of lignin-polyester blends as coating materials. Due to the abundance of functional groups in the lignin structure, it can act as corrosion inhibition centers in the coating. The coatings are deposited on stainless steel surfaces by a novel process route via atmospheric plasma powder spraying (APPS). To determine the effect of the lignin content on the corrosion performance, the specific amounts of lignin and polyester have been varied in 10 % increments from 0 % to 100 % with constant coating parameters. The as-produced coatings exhibited thicknesses that ranged from 11 μm to 30 μm, respectively for the pure lignin and polyester coatings. Additionally, scanning electron microscopy (SEM) analysis demonstrated the meltability of the lignin and polyester powder through the plasma process. Coatings containing a greater proportion of polyester exhibited superior meltability and better coverage. Furthermore, it was observed that the APPS promoted cross-linking of the lignin particles, as determined by Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). This, in conjunction with well-balanced lignin-polyester ratios, was instrumental in achieving advanced corrosion resistance as evidenced by Potentiodynamic polarization measurement (PDP). The lignin proportion between 40 % and 60 % produced the highest corrosion inhibition efficiency, with a maximum inhibition of 96 %. Furthermore, pull-off adhesion tests suggest that lignin contributes to the overall cohesive strength of the blend.