In-flight Particle Research Articles

Polymer Metallization by Cold Spray Deposition of Polyamide-Copper Composite Coatings

Cold spray metallization of polymers is a promising surface engineering technique that enables the deposition of metal coatings onto polymer substrates at low process temperatures, resulting in improved surface properties, thus enhanced functionality of the polymeric material. However, deposition of well-adhering metallic coatings without causing surface damage to the polymer substrate is still a challenge. In this work, copper-polyamide composite coatings with different copper concentrations between 30 and 75 vol.% in the starting powders were deposited on polyamide substrates using a low-pressure cold spray system with two nozzle geometries of short and long diverging sections. The spray parameters were first developed for the deposition of polyamide powder (at gas temperature of 260 °C and gas pressures ranging from 0.41 to 1.37 MPa), and then used to spray the composite powder mixtures where the polyamide particles were acting as a binder for copper particles. Inflight and impact particle characteristics (velocity and temperature) of the polyamide powder were simulated to better understand the deposition properties. Considering that the selected conditions were suboptimal for the deposition of copper particles, no surface damage was caused as no penetration of the copper particles into the polymer substrate occurred. The results show that increasing the copper content in the powder mixtures significantly improved the resulting coating uniformity and the retained copper content. In addition, the coating deposited by spraying the powder mixture with a higher copper content of 75 vol.% and using the longer nozzle yielded the highest cohesion strength. To further improve coatings cohesion, two post-spray processing methods of furnace heating and hot pressing were used, and the effect of each process on coatings properties was investigated.Please confirm if the author names are presented accurately and in the correct sequence (given name, middle name/initial, family name). Given name: [Kintak Raymond] Last name [Yu]. Also, kindly confirm the details in the metadata are correct.The author names are now correct: Kintak Raymond given name and Yu last nameAll other details are corrects

Investigation of thermal behavior of powder stream and molten pool during laser-based directed energy deposition

Laser-powder interaction and molten pool evolution are two main physical processes in laser-based directed energy deposition (L-DED), which greatly affect the morphology and quality of the deposition layer. In this research, a comprehensive three-dimensional analytical-numerical model which integrates a laser-powder interaction model and material deposition model is developed to study the multi-physics coupling characteristics in L-DED process. The concentration of the powder stream is modeled based on conservation of mass and is in good agreement with the experimental result which is captured by high-speed camera. The effects of main parameters, including laser power, powder feeding rate, powder feeding angle and defocus length on the laser attenuation and the temperature distribution of the in-flight powder particles are analyzed. The results show that the laser attenuation rate increases from 0.72% to 1.36% with the powder feeding angle increasing from 45 deg. to 65 deg-. However, the laser attenuation rate is almost the same with the defocus length of 25 mm, 35 mm and 45 mm. Moreover, the peak powder temperature on the deposition surface increases with the increase of powder feeding angle and decrease of defocus length. Accordingly, the heat and mass input conditions at the molten pool surface for the material deposition model, including powder mass flux, effective laser intensity and powder temperature are obtained from the laser-powder interaction model. The heat transport and fluid dynamics of the molten pool are discussed based on the calculated results from material deposition model. Finally, the calculated molten pool geometry shows good agreement with the experimental results with the relative error <8.5%. This work is helpful in process optimization from the point of view of adjusting the parameters related to the powder stream and deeper understanding of laser-powder interaction and molten pool evolution during the L-DED process.

Phenomenology of DSR-relativistic in-vacuo dispersion in FLRW spacetime

Studies of in-vacuo dispersion are the most active area of quantum-gravity phenomenology. The way in which in-vacuo dispersion produces redshift-dependent corrections to the time of flight of astrophysics particles depends on the model-dependent interplay between Planck-scale effects and spacetime curvature/expansion, and we here derive the most general formula for the leading order redshift-dependent correction to the time of flight for the scenario in which relativistic symmetries are deformed at the Planck scale (DSR) for the constant-curvature case. We find that, contrary to the broken symmetries scenario (LIV), where in principle any arbitrary form of redshift dependence could be allowed, for the DSR scenario only linear combinations of three possible forms of redshift dependence are allowed. We also derive a generalization of our results to the FRW case, and discuss some specific combinations of the three forms of redshift dependence whose investigation might deserve priority from the quantum-gravity perspective.

Analysis of the parameters of technological material sprinkling devices of special road vehicles (ꞷδ=const): MAN CLA 18.280 4x2 BB CS45

In this article, the size of the wheel radius of the special road vehicle (MAN CLA 18.280 4x2 BB CS45), which is widely used to increase the economic and material efficiency in the elimination of slippage on the road surface in the winter season, and to ensure traffic safety, and the height of the wheel installation o It is studied how far the technological material can be sprayed when the rotation speed is constant. Process material spreaders have equipment that is permanently attached to vehicle chassis or trailers or can be quickly detached. The supply of technological material (salt-sand) to the spreader disk, the forces acting on the technological material (salt-sand) particle during the rotation of the spreader disk were considered. The dependence of the particle flight range when the radius of the scattering disk, the height of the disk, and the angular velocity of the scattering disk have a constant value have been considered. The impact of technological material particles on the distance of a particle flying from the outer edge of the disk and falling to a certain distance, the radius of the disk, the height of the disk above the level of the carriageway, the value of the angular velocity of the disk, and the width of spraying relative to the road surface; the diameter of the sprinkling disk and the height of the sprinkling disk: the dependence of the density of sprinkling relative to the road surface, the speed of the main machine, and the speed of material delivery were studied.

Strategy to Generate Oxide-Free Molten Metal Droplets for Fully Dense Corrosion-Resistant Coatings by Atmospheric Plasma Spraying

Thermal spray techniologies are very efficient to deposit metal coatings, which have been applied to different industrial fields for protection of metals from wear and corrosion. However, severe oxidation during inflight of spray particles introduces large amount of oxide inclusions in the coating which limits lamellar bonding formation and thus full utilization of coating material performance potential. In this project, the spray powders containing the deoxidizers such as carbon and boron are designed to develop in-situ deoxidizing effect to generate oxide-free molten metal droplets by air plasma spraying (APS) in ambient atmosphere for depositing dense coatings with sufficiently bonded splats. The thermodynamic and kinetic conditions for continuous deoxidization during whole in-flight molten droplets are presented. The experiments were conducted for NiCr, NiCrCu, CuNi coatings with boron as deoxidizer and for NiAl and FeAl coatings with dispersed diamond as deoxidizer. Results show that through powder design and spray condition optimization different spray particles can be heated to temperatures from 2100°C to 2500°C. It was found that the oxide contents in all coatings decreases with increasing spray distance, which indicates that deoxidizing effect of deoxidizer is maintained during whole spray particle in-flight. The examination shows that all APS coatings present dense microstructure. The electrochemical test reveals that the corrosion only occurs to coating surface and no trace of corrosive solution penetration into coating. As a result, the corrosion-resistant metal coatings can be realized by APS in ambient atmosphere through developing in-situ deoxidizing effect and subsequently oxide-free molten droplets with using deoxidizer-containing spray powders.

Different Primary Gas Flow Rates in Determining the Flattening Behavior of In-Flight Particles in Plasma-Sprayed NiCrBSi Coatings and the Resultant Microstructure and Hardness

The flattening behavior of in-flight particles during plasma spraying is a highly intricate process affected by numerous factors. Therefore, in this work, in-flight particles (spherical NiCrBSi powder) were collected with the water quenching process, and the morphology and composition differences between the original powder particles and the melted in-flight particles were observed using scanning electron microscopy (SEM). The particle size in various states was recorded and calculated. The internal structure of the particles was analyzed to elucidate their morphology and compositions under different flow rates of primary gas (FRPG). A coating with 1.25% porosity and a hardness of 767 HV0.5 was achieved at the FRPG of 80 L/min. X-ray diffraction (XRD) and transmission electron microscopy (TEM) were used to characterize the microstructures of the obtained coatings. It was found that the as-sprayed coating had a certain amount of the amorphous phase. A noteworthy correlation was also established, wherein a decreased distance from the substrate, augmented spraying passes, and reduced amorphous phase content were interrelated. Concurrently, a noticeable influence of the tamping effect exerted by the in-flight particles on the coating was observed.

Parameters of the disc angle of a stepped plow for tillage

The development and creation of energy-saving machines and technologies for high-quality basic processing is one of main tasks today. The existing step plows for smooth, row less plowing have a number of disadvantages. With these plows, the technology of smooth plowing is carried out in conditions of a closed furrow, as a result, they do not ensure the turnover of layers the required degree and the sealing of plant residues, and also have a high energy intensity. The purpose study is to substantiate the parameters the disk angle stepped plow. Theoretical studies were carried out using the methods of classical mechanics. Analytical expressions have been obtained to determine the permissible distance of transverse discarding of soil particles by a disk angle and the range of flight of soil particles under the action disk, depending on its parameters. Theoretical studies have established that the permissible distance of transverse discarding of soil particles by a disk angle should be no more than 29 cm. The analysis of the expressions obtained showed that with an increase in the diameter disk angle-lift, its angle of installation to the pressure of movement, the angle of inclination to the vertical of depth of processing the angle-lift, the range of transverse rejection of soil particles increases. To ensure the established distance of soil discarding, the diameter of the disk angle-lift should be no more than 480 mm, its installation angle to the direction the hole should not exceed 35°, the installation angle to the vertical should not exceed 10° and the processing depth should not exceed 11 cm.

An Investigation into the Relative Efficacy of High-Velocity Air-Fuel-Sprayed Hydroxyapatite Implants Based on the Crystallinity Index, Residual Stress, Wear, and In-Flight Powder Particle Behavior.

Due to its resemblance to the bone, hydroxyapatite (HA) has been widely used for bioactive surface modification of orthopedic implants. However, it undergoes significant thermal decomposition and phase transformations at a high operating temperature, leading to premature implant failure. This investigation uses high-velocity air-fuel (HVAF) spray, an emerging low-temperature thermal spray technique, to deposit HA over the Ti-6Al-4V substrate. Coating characteristics, such as the crystallinity index and phase analysis, were measured using X-ray diffraction, Raman analysis, and Fourier transform infrared spectroscopy, residual stress using the sin2ψ method, and tribological performance by a fretting wear test. The coating retained an over 90% crystallinity index, a crystallite size of 41.04 nm, a compressive residual stress of -229 ± 34.5 MPa, and a wear rate of 1.532 × 10-3 mm3 N-1 m-1. Computational in-flight particle traits of HA particles (5 to 60 μm) were analyzed using computational fluid dynamics; it showed that 90% of particles were deposited at a 700 to 1000 m/s velocity and a 900 to 1450 K temperature with a 2.1 ms mean residence time. In-flight particle oxidation was minimized, and particle impact deformation was maximized, which caused severe plastic deformation, forming crystalline, compressive residual stressed coatings. The thermal decomposition model of low-temperature HVAF-sprayed HA particles helped to understand the implants' crystallinity index, residual stress, and tribological characteristics. Hence, this experimental and computational analysis shows that the HVAF process can be a promising candidate for biomedical applications for having strong and durable implants.

Active learning-driven uncertainty reduction for in-flight particle characteristics of atmospheric plasma spraying of silicon

The first-of-its-kind use of the active learning (AL) framework in thermal spray is adapted to enhance the prediction accuracy of the in-flight particle characteristics. The successful AL framework implementation via Bayesian Optimisation is beneficial in, first, reducing the maximum uncertainty, which greatly improves the prediction accuracy and informativeness of the existing database. Second, it reduces local uncertainty around a contrived test point that offers the capability to find improvement in a limited search area, allowing an accurate prediction around a desired test point. The dataset for Machine Learning (ML) training consists of 26 atmospheric plasma spray (APS) parameters of silicon and a further six AL-guided spray runs carried out to reduce maximum uncertainty in the initial database. On average, a 52.9% improvement (error reduction) of RMSE and an R2 increase of 8.5% were reported on the predicted in-flight particle velocities and temperatures after the AL-driven optimisation. Furthermore, the contrived test point optimisation to predict the best possible characteristics in a limited search space resulted in a three-fold increase in prediction accuracy compared to the non-optimised prediction. The AL-driven optimisation proved to be greatly beneficial for resource-intensive thermal spraying, as the framework not only allowed an accurate prediction of the in-flight particle characteristics but also found expected improvement around a desired in-flight characteristic. Furthermore, the framework uses the Gaussian Process (GP) ML model as a surrogate that generalises a global solution without necessarily involving physical and underlying mechanisms, thus extending the framework to other thermal spraying methods.

Preparation of yttria-stabilized zirconia electrolyte via atmospheric plasma spraying for metal-supported solid oxide fuel cells

Plasma spraying under low chamber pressure has been proven to be capable of preparing dense MS-SOFC electrolytes, but it is costly and inefficient. In this study, atmospheric plasma spraying (APS) as a low-cost and high efficiency alternative was attempted to prepare yttria-stabilized zirconia (YSZ) electrolyte. Different spraying distances were adopted to investigate the effects of in-flight particle states on the coating microstructure and properties. The results show that due to the YSZ particle temperature increasing with spraying distance, the YSZ splats have more internal microcracks and more regular morphologies. At the spraying distance of 80 mm, the high particle velocity and plasma heating effect combine to create a dense YSZ coating with a porosity of 3.56 %. Additionally, the nanohardness and elastic modulus of this coating reaches 15.6 ± 0.8 GPa and 209.6 ± 4.5 GPa, respectively. The MS-SOFC with the dense YSZ electrolyte, achieve a maximum power density of 902 mW⋅cm-2 and ohmic resistance of 0.10 Ω⋅cm2 at 900 °C. This work demonstrates the feasibility of APS in the efficient preparation of MS-SOFCs electrolytes through optimized particle deposition.

Laser cladding: A high-speed-imaging examination of powder catchment efficiency as a function of the melt pool geometry and its position under the powder stream

This paper provides quantitative information about the paths taken by blown powder particles during laser cladding. A proportion of the powder is “wasted” by bouncing off the solid areas surrounding the melt pool. This wastage reduces the productivity and profitability of the process. In this paper, specially developed software was used to analyze high-speed imaging videos of the cladding process, to monitor the directions of powder particle flight toward and away from the melt pool area. This information has been correlated to the geometry and position of the melt pool zone for three different cladding techniques: single track cladding (A tracks), standard overlapping track cladding (AAA cladding), and a recently developed technique called ABA cladding. The results show that the melt pool geometry, and particularly the overlap between the melt pool and the incoming powder stream, has a strong influence on powder catchment efficiency. ABA cladding was found to have considerably better powder catchment efficiency than standard AAA cladding and this improvement can be explained by consideration of the geometries and positions of the melt pools and surrounding solid material in each case. As powder costs are an important factor in industrial laser cladding, the adaption of the ABA technique, and/or control of pool/powder stream overlap (e.g., by making the powder stream not coaxial with the laser beam), could improve the profitability of the process.

Novel candidate of metal-based thermal barrier coatings: High-entropy alloy

To obtain compatible properties of low thermal conductivity and high thermal stability, Al0.6CoCrFeNiTi high-entropy alloy was designed as a novel candidate of metal-based thermal barrier coatings (MBTBCs). The corresponding high-entropy alloy coatings were fabricated by both high-velocity oxygen-fuel spraying (HVOF) and atmospheric plasma spraying (APS), and then the dependence of thermal insulation properties on microstructure was investigated. The both coatings exhibit a simple body-centered cubic (BCC) structure, but present obvious difference in microstructure and defect characters which relates to the evolution of in-flight particles. Benefit from the extremely low thermal conductivity, the APS-deposited coating can increase 13.24 °C of the surface temperature of piston crown and yield a temperature reduction of 19.00 °C along the thickness direction, which mean a positivity on enhancing the power efficiency of vehicle engines without sacrificing the strength of aluminum alloy components. In virtue of a decoupling method, the crucial effect of microstructure on thermal conductivity is disclosed, thus interpreting the excellent thermal insulation property of APS-deposited coating dominated by grain refinement and disordered BCC structure. The present results demonstrate a great potential of high-entropy alloy coatings as thermal barrier application and provide an inspiration for future works aiming to design these coatings to meet specific engineering needs.

Prediction of In-Flight Particle Properties and Mechanical Performances of HVOF-Sprayed NiCr-Cr3C2 Coatings Based on a Hierarchical Neural Network.

High-velocity oxygen fuel (HVOF) spraying is a promising technique for depositing protective coatings. The performances of HVOF-sprayed coatings are affected by in-flight particle properties, such as temperature and velocity, that are controlled by the spraying parameters. However, obtaining the desired coatings through experimental methods alone is challenging, owing to the complex physical and chemical processes involved in the HVOF approach. Compared with traditional experimental methods, a novel method for optimizing and predicting coating performance is presented herein; this method involves combining machine learning techniques with thermal spray technology. Herein, we firstly introduce physics-informed neural networks (PINNs) and convolutional neural networks (CNNs) to address the overfitting problem in small-sample algorithms and then apply the algorithms to HVOF processes and HVOF-sprayed coatings. We proposed the PINN and CNN hierarchical neural network to establish prediction models for the in-flight particle properties and performances of NiCr-Cr3C2 coatings (e.g., porosity, microhardness, and wear rate). Additionally, a random forest model is used to evaluate the relative importance of the effect of the spraying parameters on the properties of in-flight particles and coating performance. We find that the particle temperature and velocity as well as the coating performances (porosity, wear resistance, and microhardness) can be predicted with up to 99% accuracy and that the spraying distance and velocity of in-flight particles exert the most substantial effects on the in-flight particle properties and coating performance, respectively. This study can serve as a theoretical reference for the development of intelligent HVOF systems in the future.

Effect of elastic scattering between ions and neutral particles on ion transport perpendicular to magnetic fields in divertor plasmas

AbstractIn divertor plasmas, atomic processes play a significant role in reducing the divertor heat load. In particular, the elastic scattering between ions and neutral particles can be characterized as a large‐angle scattering; this is in contrast with Coulomb scattering, which is dominated by small‐angle scattering. In a large‐angle scattering, a large fraction of the ion energy is transferred to the neutral particle, and the particle flight direction can be changed significantly. This process can generate additional particle transport perpendicular to magnetic field lines and affect plasma density profile in neutral‐rich divertor regions. However, in most edge plasma simulation codes, the elastic scattering with neutral particles is not taken into account in the direction perpendicular to the magnetic field lines. In this study, we performed a 2D orbital calculation without other drifts such as diamagnetic and E × B drifts to assess the effect of the elastic scattering on the density profile. The peak density is found to be decreased by 11.1 (6.3)% compared with the model that ignores the transport due to the elastic scattering, even at 3.0 (5.0) T magnetic field similar to that of the JT‐60SA (JA DEMO reactor) class. In addition, the ion transport can be expressed as a diffusion model by integrating the differential cross section over the large‐angle scattering range . The proposed method may be easily introduced into any integrated codes to consider the elastic scattering.

Investigation on close-coupled gas atomization for Fe-based amorphous powder production via simulation and industrial trials: Part II. Particle flight and cooling during secondary atomization

A two-way coupling Discrete Phase Model (DPM) is applied to calculate the secondary atomization process. The particle flight and cooling processes are studied under different process parameters. The results show that the average particle size (d50) depends on the gas-liquid interaction and decreases with increasing gas-to-melt ratio (GMR). The standard deviation of the particle size (d84/d50) increases as the melt mass flow rate increases, and both high and low atomization pressures result in a high d84/d50. The average cooling rate of particles can be improved by reducing the melt mass flow rate and increasing the atomization pressure. By increasing the gas temperature to 400 K, the d50 can be significantly reduced and the average cooling rate can be approximately increased two times, indicating that the hot gas atomization technique can effectively improve the yield of fine amorphous powders. However, excessive gas temperature not only has a limited effect on improving the cooling rate, but also significantly increases the d84/d50 and defective particles, suggesting that the gas temperature must be matched to the atomization process to achieve ideal effects. The powders produced at 2.0 MPa and 0.075 kg·s−1 exhibit good circularity with a d50 of 58.9 μm, which is in good agreement with the simulation analysis. Moreover, the powders with sizes less than 50 μm exhibit high amorphous fraction (96.6%) and outstanding soft magnetic properties. In this work, a flow-heat transfer-DPM coupling model is established to provide theoretical guidance for the production of high-performance Fe-based amorphous powders.

ИЗУЧЕНИЕ АЭРОДИНАМИЧЕСКИХ ХАРАКТЕРИСТИК МАКРОТЕХА И ОЦЕНКА ВОЗМОЖНОСТЕЙ ЕГО ИСПОЛЬЗОВАНИЯ ДЛЯ ДИНАМИЧЕСКОЙ АЭРОЗОЛЬНОЙ СЦИНТИГРАФИИ

Introduction: The leading protective mechanism of the lungs is the processes of deposition of inhaled substances and mucociliary clearance (MCC), the optimal method for studying which is dynamic radioaerosol scintigraphy. are not available on the market. The applicant in this regard for a number of characteristics is the radiopharmaceutical from albumin, produced in the Russian Federation under the brand name Macrotech (M). It is used for perfusion scintigraphy to verify primarily pulmonary embolism and its ability to study deposition of inhalants and MCC has not been studied. Purpose: To study the aerodynamic properties of M dispersion and to determine the possibilities of its use for dynamic radioaerosol scintigraphy of the lungs in order to assess the processes of deposition of inhaled substances and MCC. Material and methods: To study the aerodynamic properties of M, on which the assessment of the deposition of inhaled substances and MCC significantly depends, we studied the dispersion of its particles in different states, and studied them in shape and morphology. An ultrasonic inhaler TuR USI-50 (Germany) generated an aerosol from a suspension of M in distilled water. To study the dispersion in air, laser spectrometry was used using the Spraytec Malvern Instruments system (Great Britain). The protein content in the initial suspension and dispersible aerosol, collected in the form of a condensate, was determined using an Immulite 2000 XPi immunochemical analyzer (Siemens, USA).The shape and morphology of the particles were studied using scanning electron microscopy using. Results: The study of the aerodynamic properties of the dispersion of M indicated that its particles are involved in the dynamics of the movement of the airflow and the flight of water particles generated by the inhaler. The dispersity of the aerosol generated from the suspension M averaged about 5 μm and did not significantly depend on the concentration of the radiopharmaceutical and did not depend on the studied dispersion intensity and airflow rate set using an inhaler. The morphology of M particles was characterized by a complex shape and roughness. Conclusion: The aerodynamic characteristics of M are not optimal for studying the processes of deposition and MCC. However, a final verdict requires a direct assessment of the deposition of the inhaled radioaerosol generated from this preparation.

Prolonged thermal durability of plasma-sprayed lanthanum hexaluminate thermal barrier coating by optimizing crystallinity

LaMgAl11O19 (LMA) with magnetoplumbite structure has been identified as a potential candidate for the next generation of thermal barrier coatings (TBCs). However, the as-sprayed LMA coating presents a large amount of amorphous phase originating from the rapid quenching from the molten droplets, which may compromise the reliability of coating during high-temperature service. A logical approach to improve LMA TBC life, therefore, is to enhance its crystallinity. In the present study, three LMA powders with different particle size distributions (fine, medium and coarse feedstocks) were utilized to deposit TBCs to investigate whether the thermal durability of LMA can be improved by increasing particle size. It was based on a hypothesis that large particle size can decrease the melting degree of in-flight particles and thus result in high crystallinity of as-sprayed LMA coating, making less recrystallization stress to enhance the thermal shock resistance of LMA coating. Results show that prolonged thermal cycling durability can indeed be achieved by increasing particle size. However, excessive particle size could lead to higher porosity derived from unmelted particles, which function as the weak regions for the coating system, thereby damaging the structural integrity and adhesive strength between the topcoat and bond coat. This could cause microcrack linking when the accumulated thermal stress exceeds its fracture toughness under consecutive heating-cooling cycles despite its higher crystallinity. Concerning the coating fabricated by medium powder, it achieves the optimal balance of crystallinity and structure integrity, resulting in the longest thermal cycling lifetime. The results provide guidance for the development and design of high thermal durability LMA TBCs. When optimizing the recrystallization stress within the coating, attention should be paid to improving its bonding strength simultaneously.

Analysis of the Impact of Rdf Combustion on Cement Clinker Quality in a Superstoichio-Metric Oxy-Fuel Atmosphere by Cfd Simulations

ABSTRACT Superstoichiometric oxygen combustion (i.e. the oxygen content during combustion is larger than required for the complete conversion of the fuel), also called pure-oxy-fuel, is a novel concept to reduce CO2 emissions from the cement clinker production. In the current contribution, we examine in a simulation study the influence of superstoichiometric combustion in combination with the use of refuse-derived fuel (RDF) of different composition and particle size on process parameters and cement clinker quality in the rotary kiln. A comparison with a standard fuel, namely lignite, and a conventional air-fired kiln is presented. The specific models developed to determine the flight and combustion behavior of RDF particles, which are of complex shape and significantly larger than pulverized coal, are described. The simulations conducted show that some RDF fractions react only partially in the gas phase due to their relative large size. Unburnt RDF particles reach the clinker bed, where they continue to react. In addition, for RDF, gas-phase temperature and the clinker temperature are different along the kiln length compared to coal, influencing the local mineralogical reaction in the clinker bed. However, in summary, similar clinker qualities could be obtained also compared to a standard air-fired kiln.

Tailoring microstructural features of Cr3C2-25NiCr coatings through diverse spray variants and understanding the high-temperature erosion behavior

Thermal sprayed Cr3C2-NiCr coatings are widely used to protect industrial components from ambient or elevated erosive degradation. Various thermal spraying techniques such as plasma spray, detonation spray (DS), high velocity oxy-fuel (HVOF) and high velocity air-fuel spray (HVAF) are widely used to deposit Cr3C2-NiCr coatings. The choice of thermal spraying technique governs the inflight particle velocity and temperature, resulting in unique coating microstructural features, characteristics and erosion performance. In this study, Cr3C2-NiCr coatings are deposited through HVAF, DS and axial plasma spray. A comprehensive comparative analysis was performed to understand the process-structure-property relationship of Cr3C2-NiCr coatings, which correlated with the room and high temperature erosion performance. HVAF spray deposited Cr3C2-NiCr coatings with preferred microstructural features and properties, ensuring superior (high/room temperature) erosive resistance. Cr3C2-NiCr coatings deposited via DS spray performed second best, while plasma sprayed exhibited defective microstructure with inferior mechanical properties, resulting in substandard erosion performance.

Effects of modification of hBN by nickel plating on coating structure and properties of supersonic plasma spraying NiCr-Cr3C2-hBN@Ni coatings

Hexagonal boron nitride (hBN) with excellent self-lubrication performance is expected to relieve the friction resistance and wear of NiCr–Cr3C2 coatings. However, the poor wettability of hBN with most materials makes it difficult to fabricate NiCr–Cr3C2-hBN composite coating with good cohesion strength. In this study, hBN was firstly pretreated through magnetron-sputtering aided Ni plating to form hBN@Ni particles. Then, NiCr–Cr3C2-hBN@Ni powder was prepared by spray granulation. Next, corresponding coatings were prepared through supersonic atmosphere plasma spraying. It was found that in comparison with NiCr–Cr3C2-hBN coating, the NiCr–Cr3C2-hBN@Ni coating exhibited a decreased porosity (from 3.6% to 0.3%), elevated cohesion (from 52.78 N to 62.11 N), and the wear rate decreased by an order of magnitude. It was concluded that hBN@Ni can effectively improve the component interface inside powder, enhance the cohesion of molten in-flight particles, and make the internal structure of the coating denser.