Thick Coatings Research Articles

Discrete Element Modeling of Fracture Behavior of Thermal Barrier Coatings Under Bending Conditions

Abstract The bending-driven failure test is a reliable and efficient method for evaluating the quality and load-bearing capacity of thermal barrier coatings (TBCs). This study utilizes the discrete element method (DEM) to examine the damage evolution behavior and mechanical properties of TBCs with two different coating thicknesses under four-point bending (4PB) conditions at the microscale. The results reveal that during the bending process, both thin and thick coatings experience tensile instability fractures and the formation of transverse cracks perpendicular to the interface, with crack spacing ranging from approximately 1 to 2 times the coating thickness. Thicker coatings exhibit larger crack spacing and a significantly higher delamination damage evolution rate at the interface compared to thinner coatings, displaying more pronounced delamination characteristics. While thick coatings demonstrate stronger deformation resistance, their higher bending modulus and load-bearing capacity lead to the accumulation of more cracks under equivalent strain conditions, increasing the risk of crack propagation and failure. Additionally, the pores in the coating's microstructure promote crack branching and deflection, resulting in an expanded fractured area and a negative impact on the TBC system's lifespan. This study also analyzes variations in the load-displacement curve, particle contact states, strain energy, and acoustic emission (AE) counts. By integrating experimental results, it explores the relationship between different load stages and coating damage evolution. These findings provide a theoretical basis for identifying coating failure modes in 4PB tests and offer valuable insights for the design and optimization of TBC performance.

Experimental Investigation and CALPHAD Calculation Concerning the Effect of Cooling Rate and Coating Thickness on the Industrial Al-Zn Coated Product

Experimental Investigation and CALPHAD Calculation Concerning the Effect of Cooling Rate and Coating Thickness on the Industrial Al-Zn Coated Product

Effect of TiC Coating Thickness on Carbon Fiber Surface on Microstructure and Properties of Aluminum Matrix Composites

In this paper, the synthesis of TiC-coated carbon fibers (TiC-CFs) with varying thicknesses is achieved through the manipulation of the molten salt reaction, along with the fabrication of TiC-coated carbon fiber-reinforced aluminum matrix (TiC-CF/Al) composites via the vacuum pressure infiltration technique. The results show that modulating the holding time of the molten salt reaction significantly enhances the wettability between the carbon fiber (CF) and the aluminum, thereby augmenting the mechanical integrity of the composite materials. Should the holding time be excessively short, the coating on the CF surface develops an uneven distribution, and its efficacy in obstructing the direct interaction with the aluminum is inadequate. As the holding time prolongs, the TiC coating thickens, achieving a comprehensive coverage after 2 h of holding. The presence of a pristine TiC coating on the CF surface not only optimizes the wettability with the aluminum melt but also mitigates the reaction between the CF and aluminum. However, an excessively thick coating not only reduces the strength of the fibers, due to excessive reactions, but also makes the coating prone to detachment during the preparation process due to stress. At a holding time of 3 h, the tensile strength of the CF/Al composite material reaches its highest value, with a tensile strength of 103.93 MPa and an impressive 72.35% enhancement over that of the aluminum.

Polyethylene Terephthalate‐Based Heat Sealable Packaging Film Without Heat Sealing Layer

ABSTRACTThe food packaging industry is evolving to meet demands for circularity, cost‐effectiveness, lower carbon footprint and higher production efficiency with polyethylene terephthalate (PET) emerging as a preferred material for packaging. Despite its advantages, PET faces two main challenges in flexible barrier packaging applications, such as flow packs or form‐fill‐seal pouches. First, PET films for flexible packaging often lack adequate moisture and oxygen barriers, limiting their range of applications. Second, the high melting temperature of PET of around 250°C complicates the sealing process, causing deformation and poor‐quality seals. Traditional solutions involve multilayer films, in which PET is laminated with a superior permeation‐barrier layer and a lower melting‐temperature heat‐sealing layer. This results in nonrecyclable packaging, posing sustainability issues. In the present work, PET‐based heat sealable films were developed to address these issues. Specifically, a water‐based organic–inorganic hybrid nanocomposite sol–gel coating was applied to one side of the 23‐μm thick PET film, followed by drying and curing. The thickness of the subsequent coatings was approximately 2.3 μm. The sol–gel's rheological properties allow for a microscopically thin application that hardens into a micrometre‐thick, flexible, transparent and abrasion‐resistant coating with a decomposition temperature well above melting temperature of PET. The wettability of the coating was slightly higher than that of PET. The result of the pencil hardness test indicates tight bonding of the coating to the PET film. Mechanical tests of the coated and uncoated PET indicate that the mechanical properties of the bulk PET were retained after the application and curing of the coating, and the reinforcing effect of the coating was confirmed by the measurement of the Young's moduli and the puncture resistance test. Characterization using Fourier transform infrared spectroscopy confirms that the film contains organo‐silicon compounds and aluminium oxides. Uncoated sides of a pair of PET films were faced and heat‐welded at 250°C, demonstrating significantly reduced deformation around the welding portion. The coating reduced oxygen and water vapour transmission rates by more than a factor of 3 and 4, respectively.

Metallic Coatings in the Diagnosis of Run‐Away Electrons in Magnetic Confinement Fusion Facilities

AbstractThe article presents the application of a low‐temperature plasma technique accomplished by controlled arc discharges in ultra‐high vacuum deposition of metallic coatings on ceramic substrates. Such metallic coatings are very important in the diagnostic devices within the magnetic confinement fusion facilities, especially in small and medium‐sized tokamaks. The application of molybdenum coating on the diamond substrate necessary for Cherenkov‐type detectors applied as a runaway electron diagnosis is an example of such an application in diagnostic techniques. Presented research focused on the structural analysis of molybdenum coatings and the influence of different synthesis parameters on coatings' diverse structures and thicknesses. The stability of molybdenum coatings is explored using the Rod Plasma Injector IBIS2 facility. Pulsed plasma interactions induced noticeable surface changes, mirroring the destruction observed after exposure to up to 10 plasma pulses. In addition, the characteristics of Cherenkov detector molybdenum coating destruction after experimental campaigns are presented.

Solvation enabled highly efficient gradient assembly creates robust metal-phenolic coatings.

Solvation enabled highly efficient gradient assembly creates robust metal-phenolic coatings.

Assessing the link between skin Aquaporins and morphological attributes under simulated heat stress conditions: A comparative investigation between hair and wool sheep breeds.

Assessing the link between skin Aquaporins and morphological attributes under simulated heat stress conditions: A comparative investigation between hair and wool sheep breeds.

An Investigation into the Plasma Spraying Process for Depositing a Thick Coating on a Superalloy Substrate from Additive Manufacturing

An Investigation into the Plasma Spraying Process for Depositing a Thick Coating on a Superalloy Substrate from Additive Manufacturing

In English

In this study, hybrid organosilica coatings on glass substrates were synthesized using mixtures of the active polymer OH-terminated PDMS and one or more precursors, namely methyltrimethoxysilane bis(3-trimethoxysilylpropyl) amine, phenyltrimethoxysilane, cyanopropyltrimethoxysilane, aminopropyltriethoxysilane in the presence of modifiers (polyethylene glycol, organic solvents) and trifluoroacetic acid catalyst. The aim of this work was to obtain new sorption materials for the extraction of nonpolar and semi-polar analytes, for example, carbonyl compounds in the form of PFBHA derivatives, azo dyes, phthalates, and others, and to purify samples with a complex matrix for further gas chromatographic analysis. The advantages of the obtained sorption coatings are the effective separation of micro quantities of target compounds of nonpolar and semi-polar nature from polar compounds present in aqueous samples in rather high concentrations. The paper describes the synthesis of organosilica coatings of various compositions, the volume ratio of the active polymer, precursors, deactivating agent, catalyst, and modifiers. The coatings were applied to glass substrates using two methods: spin-coating and dip-coating. Sometimes the application was complicated due to uneven distribution of the sol when the solution mixture was too viscous or required a long drying time. Bis(3-trimethoxysilylpropyl) amine and N-(2-aminoethyl)-3-aminopropyltriethoxysilane proved to be effective crosslinking agents with similar properties of the obtained coatings; the addition of these precursors significantly improved the characteristics of the obtained coatings. It has been shown that mixtures containing OH-terminated PDMS form thick coatings (up to 325 μm) without cracks in the presence of most of the studied precursors, and the addition of titanium isopropoxide improves the thermal stability and leads to the formation of a more uniform coating in the case of substrates of complex shape (stir bars). The IR spectra of the studied coatings were obtained, most of the spectral bands are typical of the PDMS polymer, and the presence of covalently bound titanium in the coatings is confirmed by a peak at 924 cm–1. All the coatings were hydrophobic, and the contact angles with water were measured, which ranged from 99.7 to 105.6. Thermogravimetric analysis (TG and DTA) was performed to verify the thermal stability of the coatings for further use in solid-phase microextraction with gas chromatography, and it was shown that the coatings could withstand heating up to 350–425 ℃. For sorption in analytical quantitative methods, it is necessary to use coatings that are homogeneous, uniform, durable, less prone to swelling, and reproducible in synthesis and during sorption. The synthesized coatings are effective for further use in chemical analysis to purify samples from interfering components or for preconcentration of analytes. The coatings have sufficient stability to be used in the hybrid methods of analysis.

Development of a Small‐Scale Coating Thickness Detection Robot for Plane Steel Gate Panel

ABSTRACTA small‐scale coating thickness detection robot with remote wireless control was developed to solve the problems of high labor intensity, safety hazards, and lack of special automated equipment for plane steel gate panel coating thickness detection. The robot adopted a chain mechanism and permanent magnet to realize the adsorption crawling on vertical panels, and a 180° reversible detection bench was designed to realize the conversion between panel coating thickness detection operation and panel cleaning operation. The operation flexibility was improved by the x‐axis and z‐axis movement control mechanism; it made the robot capable of adjusting the detection position while parked. The main crawling posture of the robot on the panel was analyzed, and the magnet adsorption force and crawling driving torque were determined. The remote control system was designed, and the robot crawling, detection position adjustment, camera screen, and data transmission display, and so on, could be controlled by the control page, making the robot easy to operate. Finally, it was verified that the detection robot can stably adsorb and crawl within the load of 2 kg, the error of coating thickness detection does not exceed the allowed range of 5%, and the surface of the panel after brush cleaning can meet the requirements of the detection. The stability and accuracy of the detection robot can meet the actual needs of plane steel gate panel coating thickness detection, can replace manual operation to reduce labor intensity and safety hazards, and further enhance the development process of intelligent equipment in the water conservancy industry. This study can provide some help for the development and application of this kind of robot.

Monte Carlo simulation of secondary electron yield of Al2O3 coatings with an extensive three-layer model

Abstract Based on the first principles combined with Monte Carlo method, the secondary electron emission characteristics of Al2O3 coating on Si substrate is studied in this work. Due to the differences of secondary electron yield between the Monte Carlo simulation with Al2O3/Si double-layer structure and the experimental results, a new three-layer structure is proposed. A layer of SiO2 is introduced between Al2O3 and Si according to atomic ratio detected by the experimental data. The simulation results with three-layer structure Al2O3/SiO2/Si are in good agreements with the experimental results. Two interface potential barriers of Si/SiO2 and Si/Al2O3 are formed when SiO2 exits. As a result, it is more difficult for electrons excited in Si to penetrate into the Al2O3 coating. Compared with double-layer structure, secondary electron yield is lower when the energy of primary electrons is high. With the growth of thickness of Al2O3 coatings, secondary electron yield increment decreases. When the thickness of the coating increases to 7 nm, internal secondary electrons are almost all excited in the Al2O3 coating.

A comparative study on erosion wear behavior of bilayered high velocity oxy‐fuel ceramic coatings on aluminum alloy substrate using granite and quartz erodent

AbstractHigh velocity oxy‐fuel coatings have been sprayed on a novel aluminium (Al) alloy substrate with varying coating thickness and tested for their wear behavior. The air erosion wear test has been conducted on coating samples using Granite stone powder and quartz sand of size up to 75 μm as erodent. The steady state experiments indicate that the greatest specific erosion rate is at 90° for erosion by granite sand and at 60° for erosion by quartz sand. The specific erosion rate decreases with the increase in the thickness of the coatings. Surface topography of the eroded samples indicate an increase in surface roughness at 90° as compared to that at 60° impact angle. Thereafter, Taguchi (L16) orthogonal array is utilized in order to optimize the input parameters. The input parameters are impact velocities, Coating thickness, Erodent feed rate and impact angle. The results from Taguchi experiments find the order of dominance of control factors as: velocity > angle > coating thickness > erodent feed rate for erosion by granite stone and velocity > coating thickness > angle > erodent feed rate for erosion by quartz sand. Coatings have exhibited a semi‐ductile wear behavior.

Modeling and Experimental Analysis of Bias Voltage Effects on Hardness and Thickness of TiN Coatings Produced by PVD Process

This study examines the impact of bias voltage on the mechanical properties and film thickness of TiN coatings deposited on cold work tool steel via the PVD process. TiN coatings, known for their excellent hardness and wear resistance, were deposited at varying bias voltages (100–300 V). Hardness measurements and SEM analyses were conducted to evaluate the relationship between bias voltage, hardness, and film thickness. Theoretical models, including hardness-load and indentation hardness relationships, were developed to provide a comprehensive understanding of these trends. The results demonstrate that increasing the bias voltage enhances coating hardness up to 250 V due to improved atomic mobility and nucleation density. However, beyond this threshold, grain coarsening and defect formation contribute to a reduction in hardness. A monotonic decrease in film thickness was observed with higher bias voltages, attributed to ion bombardment and re-sputtering effects. The developed models showed strong alignment with experimental results, particularly for indentation hardness behavior, while discrepancies in the hardness-load relationship were noted under high loads and higher bias voltages. These findings underscore the importance of precise bias voltage control and theoretical modeling in enhancing TiN coating performance for industrial applications.

Determination of thermostressed state of cylindrical bodies with multilayer inhomogeneous coatings

The method of determining the thermal stress state in a long cylinder with the inhomogeneous in the radial direction multilayer coating under a constant force surface load and a given temperature field is proposed. The corresponding problem of uncoupled thermoelasticity in terms of stresses is reduced by direct integration of the equations of equilibrium and compatibility to a set of integral equations relative to radial stresses and the sum of radial and circular stresses. The approximate analytical solutions to these integral equations were obtained taking into account the thinness of each coating layer. The method was verified by comparison with the results obtained from the exact solutions of the cor¬responding thermoelasticity problem for the power-law dependence of the thermomechanical characteristics of the coating materials on the radial variable. The method can be applied to determine the thermal stress state of the relatively thick coatings which consist of a large number of thin ones.

Optimizing Boride Coating Thickness on Steel Surfaces Through Machine Learning: Development, Validation, and Experimental Insights

Optimizing Boride Coating Thickness on Steel Surfaces Through Machine Learning: Development, Validation, and Experimental Insights

Study on the Relationship Between WC Coating Thickness and Residual Stress Using Critical Refracted Ultrasonic Longitudinal Waves

Tungsten carbide (WC) coatings of varying thicknesses were prepared using electrical discharge deposition technology. Relevant characterizations were conducted to analyze the residual stress in the WC coatings from a microscopic perspective, and this residual stress was measured using X-ray diffraction technology. Under isothermal conditions, a novel method for detecting the residual stress of the coatings utilizing critical refractive longitudinal (LCR) waves was employed to investigate the relationship between the residual stress of the WC coatings and their thickness. According to acoustic elastic theory, LCR stress measurement is based on the principle that stress within the material alters the propagation characteristics of ultrasonic waves. After correcting the effect of coating thickness on LCR propagation, the detection results of the LCR wave indicate that the compressive stress present in the coating may cause the substrate to exhibit a certain degree of tensile stress. At a coating thickness of 6–13 µm, as the thickness of the WC coating increases, the residual compressive stress within the coating gradually rises, leading to an increase in tensile stress on the substrate. However, at coating thicknesses of 13–16 µm, the changes in tensile stress on the substrate become minimal or even decrease, despite the continued increase in compressive stress within the WC coating. The relationship curve derived from the matrix surface aligns more closely with a quadratic function, while the curve obtained from the coating surface corresponds more to a linear function. This study employs LCR waves to detect residual stress in coatings, and the results indicate that LCR waves hold significant potential for application in the field of residual stress detection in coatings.

EVALUATION OF THE DIELECTRIC AND SEMI-CONDUCTOR COATING EFFECTS ON THE MICROWAVE ABSORPTION PROPERTIES OF METALS

This research evaluated the effects of dielectric and semiconductor coatings on the microwave absorption properties of three metals: aluminum, copper, and zinc. Using COMSOL Multiphysics software, simulations were performed to analyze the interaction of microwave radiation with these metals, both in their uncoated form and when coated with dielectric and semiconductor materials of varying thicknesses. The study involved creating geometric models, applying material properties, and conducting frequency domain analyses to determine absorption characteristics. The results revealed that coating thickness played a critical role in improving microwave absorption. Optimal thicknesses for dielectric coatings reduced reflectivity and provided impedance matching layers that facilitated greater microwave penetration. Semiconductor coatings further increased absorption due to their tunable conductivity and effective loss mechanisms, which efficiently converted microwave energy into heat. Aluminum and copper exhibited low absorption in their uncoated form due to high electrical conductivity and reflectivity, while zinc displayed moderate absorption. When coated, all three metals demonstrated significantly enhanced absorption, with the impact varying based on coating type and thickness. These findings have significant implications for applications in electromagnetic interference (EMI) shielding, microwave devices, and materials science. By understanding the influence of coating thickness on microwave absorption, this study provides insights for optimizing material designs and tailoring coating parameters to enhance performance for shielding technologies and microwave absorption applications. This research highlights the potential of coatings to overcome the limitations of metals and improve their functionality in diverse technological and industrial fields.

In Situ Spray Bead Acquisition and Analysis for Coating Thickness Predictions

Coating thickness is considered to be one of the most important characteristics of thermal spray coatings. Therefore, it has long been the goal to be able to predict the coating thickness that ensues when coating an arbitrary part. A commonly applied approach is to determine the coating deposit based on a series of spray spot tests and use that for modeling the coating. Another option is to conduct spray bead tests, which better reflect the conditions during the coating. This work suggests a novel approach for in situ acquisition of the spray beads and their analysis. The acquisition is based on a 3D camera to scan the sample before and after depositing of a spray bead. The approach allows for their streamlined evaluation, enabling better understanding of spray bead formation and their modeling. The suggested analysis of spray beads includes uncertainty evaluation. This enables estimation of model prediction uncertainties which has been omitted in the previous works on the topic. The analysis shows that a relative expanded uncertainty of 10% (at 95% level of confidence) can be expected for the coating thickness prediction for the simplest scenario of coating a flat sample sprayed perpendicularly at a constant spray distance and spray speed.

Pulse width effects on microstructure and electrochemical properties of DLC coatings deposited on high-strength Al alloy

Abstract This study employed cage-like hollow discharge plasma-enhanced chemical vapor deposition (PECVD) to synthesize diamond-like carbon (DLC) films on the 2024 aluminum alloy. The DLC coatings were deposited using varying pulse widths. The microstructural and mechanical properties of the films were evaluated using scanning electron microscopy (SEM), x-ray diffraction (XRD), atomic force microscopy (AFM), Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), Nano Indenter G200 device, and a tribometer model (MS-T3001). The anticorrosion behavior of the coatings in a 3.5 wt% NaCl solution was investigated using a range of electrochemical techniques. The results showed that increasing the pulse width to 20 μs led to the deposition of thicker films due to enhanced plasma density and deposition rate. Corrosion measurements revealed lower corrosion and passive current densities as pulse width increased. This behavior can be attributed to the thicker DLC film, which effectively reduces the presence of pores and inhibits corrosive species from attacking the bare alloy. Additionally, this study calculated and reported the thermodynamic corrosion parameters, including enthalpy of activation (∆H), entropy of activation, and activation energy (∆E) for the sample.

Evaluation of 3D seed structure and cellular traits in-situ using X-ray microscopy

Phenotyping methods for seed morphology are mostly limited to two-dimensional imaging or manual measures. In this study, we present a novel seed phenotyping approach utilizing lab-based X-ray microscopy (XRM) to characterize 3D seed morphology, internal structures, and cellular analysis from a single scan. Seeds of pennycress (Thlaspi arvense L.) an oilseed cover crop, were scanned and segmented using a machine learning model. Seed morphological analysis and a coat thickness map was applied to compare seed volumes of four genotypes. Notably, the 3D seed volume measurement alone was not enough to reveal differences in seed coat between the genotypes. Applying a seed coat thickness map revealed that the Large-Golden genotype had a thinner seed coat compared to wildtype despite a greater seed coat volume. Cellular analysis showed that cotyledon cell size was a driving factor for larger seeds. XRM was compared to traditional seed morphology traits and positive correlations were observed. Between Large-Golden and wildtype, differences could only be resolved by XRM highlighting the limitations of 2D seed area measures. These results demonstrate that XRM can provide quantitative measures extracted from seeds for enhancing our understanding of seed structure, development, and facilitate breeding efforts for enhanced seed quality and crop performance.