Thick Coatings Research Articles

Measurement report: Characteristics of airborne black-carbon-containing particles during the 2021 summer COVID-19 lockdown in a typical Yangtze River Delta city, China

Abstract. Black-carbon-containing (BCc) particles are ubiquitous in ambient air, significantly contributing to particulate matter (PM) pollution. The unexpected outbreak of the COVID-19 pandemic in the summer of 2021 prompted a localized and prolonged lockdown in Yangzhou, situated in the Yangtze River Delta, China. This lockdown led to significant alteration of local anthropogenic emissions, while neighboring cities continued regular operations, providing a unique opportunity for the investigation of BCc particle characteristics influenced by varying emission conditions. Single-particle aerosol mass spectrometer (SPA-MS) analysis revealed a notable decrease in the proportion of freshly emitted BCc particles during the lockdown (LD) period. However, PM2.5 concentrations remained relatively unchanged, with an observed increase in the proportion of aged BCc particles during LD compared to the period before the lockdown (BLD). The study also underscores the significant role of regional transport in PM2.5 pollution during the campaign. Moreover, reactive trace gases (e.g., NOx, SO2, and volatile organic compounds – VOCs) could form thick coatings on pre-existing particles, likely via enhanced heterogeneous hydrolysis under high relative humidity (RH), resulting in significant BCc particle growth (∼ 600 nm), as well as PM2.5 concentration, during LD. Our study highlights that short-term, strict local emission controls may not effectively reduce PM pollution due to the complex production and transmission characteristics of BCc particles and the nonlinear responses of PM2.5 to its precursors. Achieving further effective PM2.5 reduction mandates a focus on nuanced control of BCc particles and necessitates a comprehensive and extensive approach with a regionally coordinated and balanced control strategy through joint regulation.

Investigation on Microstructures, Hardness, Friction, and Wear of Cold Sprayed Ti6Al4V Coatings With Coating Thickness of 100-3000 µm

The effect of coating thickness (CT) on the microstructures, hardness, and wear of cold sprayed Ti-6Al-4V (CS-Ti64) coatings was systematically investigated since the prolonged high pressure CS deposition could change their microstructures and porosity levels. In addition, the CT was relatively important for their durability, performance, and service life. Therefore, the CS-Ti64 coatings with different CT of 100-3000 µm were prepared on commercially available Ti64 (CA-Ti64) substrates via high pressure CS processes. The CS-Ti64 coatings had low porosity levels wherewith severely deformed Ti64 particles with a crescent-shape could be seen in their cross-sectional microstructures. The hardness of the CS-Ti64 coatings increased with increased CT probably due to their lowered bulk porosity levels associated with longer high pressure CS deposition. As a result, the increased CT from 100 to 3000 µm resulted in a 9.8% decrease in the wear of the CS-Ti64 coatings. The wear of the CS-Ti64 coating with 3000 µm was 16.8% lower than that of the CA-Ti64 as all the CS-Ti64 coatings had lower wear than the CA-Ti64. It could be concluded that the prolonged high pressure CS deposition for the thick CS-Ti64 coatings had an influence on their porosity, hardness, and wear.

Effect of deposition parameters on structural and mechanical properties of Novel h-BN doped TiCrNbN coatings

In this paper, the novel h-BN doped TiCrNbN thin films was deposited on the DIN 1.2714 steel using closed field unbalanced magnetron sputtering (CFUBMS) technique with variable working pressure, bias voltage, and LaB6 target voltage. The main goal is to determine the contribution of degrees of these parameters on structural and mechanical properties using Analysis of Variance (ANOVA). The deposition parameters were leveled based on L9 (33) orthogonal Taguchi design method. Microstructural and thickness of coatings were investigated using SEM. The coatings had granular and flawless surface properties. The thickness of the coatings was determined in the range of 874 nm and 1.69 μm. The deposition parameter that has the highest contribution to coating thickness is working pressure. Hardness and adhesion strength of coatings were determined employing nanohardness and scratch tester, respectively. The highest hardness among the coatings was 24.67 GPa, obtained with the 3x10-3 Torr working pressure, 100 V bias voltage and 600 V LaB6 target voltage parameters. The deposition parameter that has the highest contribution to hardness is working pressure. The coating conditions with the highest hardness exhibited the highest adhesion strength. The superiority of the contribution of working pressure on the adhesion strength was prominent compared to other parameters.

A non-destructive measurement method for thermal barrier coating thickness in a robot polishing process based on point cloud processing

The adhesion state between the bond coat and top coat of thermal barrier coatings (TBCs) is influenced by the surface roughness of the bond coat. Under certain operating conditions, polishing is employed to reduce the surface roughness of the bond coat, thereby enhancing the adhesion strength between the top coat and bond coat and improving the TBC’s resistance to high-temperature oxidation. In order to accurately control the thickness of the bond coat during the polishing process, this study proposes a non-destructive measurement method for coating thickness based on point clouds. By preprocessing, registering, and calculating the distance between the point cloud generated by laser scanning the turbine blade, the thickness of the bond coat was determined. The method exhibits greater accuracy in regions with small curvature variations. Compared to measurements obtained using a metallographic microscope, the maximum thickness deviation between the two methods is 4.004 μm, and the relative error is less than 5%. Experimental results demonstrate that this method can accurately measure coating thickness, offering advantages such as real-time processing, flexibility in application scenarios, high measurement efficiency, and relatively low requirements for coating materials.

ФИЗИКО-ХИМИЧЕСКИЕ СВОЙСТВА МОДИФИЦИРОВАННЫХ БИТУМНЫХ ПРАЙМЕРОВ ДЛЯ ПРОТИВОКОРРОЗИОННОЙ ЗАЩИТЫ СЕЛЬСКОХОЗЯЙСТВЕННОЙ ТЕХНИКИ И ОБОРУДОВАНИЯ

Compositions based on bitumen primers can be used for anti-corrosion protection of agricultural machinery and equipment. Their physicochemical properties were studied. It has been shown that the thickness of coatings, which is responsible for the effectiveness of barrier protection, increases as expected with an increase in the number of applied coating layers, and decreases even with a slight increase in temperature and with an increase in the amount of solvent in the case of coating by dipping. Increasing the amount of solvent added to the bitumen primer from 40 wt. % up to 67 wt. % leads to a reduction in coating thickness by 55 times. Brush application produces thinner finishes than dip application. Moisture absorption for modified BP with 67 wt. % solvent is 1-2 orders of magnitude higher than that of BP with 40 wt. % white spirit, therefore, a decrease in protective effectiveness can be expected for these materials. According to experimental studies, the contact angles for the original BP exceed 900C, which indicates the presence of hydrophobic properties. The type and concentration of additives affect the contact angles. Introduction 5 wt. % of modifying additives, paraffin P2 and Emulgin, reduces the contact angle of BP, the addition of KO-SZhK, on the contrary, increases it, improving hydrophobic properties. BP with 40 wt. % white spirit, including those with additives, shows good adhesion to carbon steel 0.8 kp. At 67 wt. % solvent in the presence of drying oil and unrefined sunflower oil additives, adhesion worsens. Viscosity-temperature dependences in semi-logarithmic coordinates for modified BP are close to linear in the temperature range 20 -60 0C with a high approximation reliability index R2 = 0.9543 - 0.9833. Based on the physicochemical properties, high anti-corrosion properties can be assumed.

Технология получения вакуумных ионно-плазменных износостойких покрытий

A review of the technologies of vacuum ion plasma (VIP) coating spraying based on the reasonability of science intensity, its criteria and evaluation methods is carried out. The technological features of producing VIP coatings are viewed with the emphasis on the process of coating formation on a substrate, which occurs under the impact of the most powerful forces in nature, i.e. these are forces of interatomic interaction. This leads to a very high level of cohesive strength of the coatings, which results in wear resistance and corrosion resistance. This leads to a very high level of cohesive strength of the coatings, succeeding in wear and corrosion resistance. Methods of research, diagnosis and testing of VIP coatings, due to the peculiarities of their structure and properties, include, as a rule, equipment and techniques of leading world manufacturers in the field of electron microscopy, microrentgen spectral analysis, diffraction analysis, X-ray photoelectron spectrometry, continuous and dynamic indentation, bench testing of unique properties. With respect to scientific and practical activities of the authors, examples of coatings of various nature (nitride, carbon, metalloceramic), different architectures (monolayer – single-phase, multilayer – 2D composites, dispersed – 3D composites) and various applications (wear–resistant, tribotechnical, antierosion, thermal barrier) are given. In particular, some types of nitride coatings TiN, TiAlN, CrAlSiN, which are characterized by high hardness H  24 GPa and abrasive wear resistance, are in the focus. However, in conditions of relatively smooth sliding friction, only the multiphase nanostructured CrAlSiN coating retains wear resistance. In conditions of drop-impact erosion, nanocompositional multilayer VIP coatings of TiN/MoN composition demonstrate the highest resistance, which compete with the recognized champion in this field - welded plates of stellite VZK (WCoCr). Despite the fact that the thickness of the VIP coatings viewed in the paper is a film of 1...10 microns, whereas the stellite plates have a thickness of at least 4 mm. In conclusion, it is noted that VIP technology continues to develop new materials, for example, to create diamond-like coatings or coatings made of high-entropy alloys. VIP technology corresponds to a high level of science intensity, and VIP coatings are promising for putting to use in mechanical engineering.

On effective surface elastic moduli for microstructured strongly anisotropic coatings

The determination of surface elastic moduli is discussed in the context of a recently proposed strongly anisotropic surface elasticity model. The aim of the model was to describe deformations of solids with thin elastic coatings associated with so-called hyperbolic metasurfaces. These metasurfaces can exhibit a quite unusual behaviour and concurrently a very promising wave propagation behaviour. In the model of strongly anisotropic surface elasticity, strain energy as a function of the first and second deformation gradients has been introduced in addition to the constitutive relations in the bulk. In order to obtain values of surface elastic moduli, we compare dispersion relations for anti-plane surface waves obtained using the two-dimensional (2D) model and three-dimensional (3D) straightforward calculations for microstructured coatings of finite thickness. We show that with derived effective surface moduli, the 2D model can correctly describe the wave propagation.

A mechanical TiAl/TiAlN multinanolayer coating model based on microstructural analysis and nanoindentation

A finite element model reproducing the mechanical behaviour during nanoindentation tests on Ti0.67Al0.33/Ti0.54Al0.46N multilayer coatings was developed. Coatings with two different nanoperiods (10 and 50 nm) were deposited by radio-frequency magnetron sputtering from a single sintered titanium/aluminium target using the reactive gas pulsing process. X-ray diffraction and transmission electron microscopy confirmed the multilayer stacking of the coatings. The finite element models of coatings with these two stacking periods were built considering successive hypotheses: equal thicknesses for metal and nitride nanolayers stacked without transition layer, equal thicknesses stacking with a transition layer between each metal and nitride nanolayer and finally imbalanced thicknesses stacking with a transition layer. The elastic and plastic properties of the stacked nanolayers were determined on thick monolithic coatings of metal and nitride using indentation testing and the finite element model updating method respectively. The elastic-plastic properties of the interface were introduced in the multilayer model as a rule of mixtures of the metal and nitride properties using two hypotheses: parallel or serial. For 50 nm-period film, the interface has a negligible effect on the overall indentation response. On the other hand, for the 10 nm period, the imbalanced stacking model with precise knowledge of the transition layer thickness obtained by N K-edge electron energy loss spectroscopy is required to reproduce the experimental indentation curve. Compared to classical analytical models accounting for hardness, not only the hardnesses but also the indentation moduli appear to be well predicted and evaluated in this work.

Degradation of LaPO4-8YSZ composite thick thermal barrier coatings by molten calcium-magnesium-aluminosilicate

The effect of LaPO4 content on the calcium-magnesium-aluminosilicates (CMAS) corrosion resistance of the plasma-sprayed LaPO4-8YSZ composite coatings at 1250 °C was investigated. The microstructure and corrosion products of the LaPO4-8YSZ composite coatings after CMAS attack was determined by using SEM/TEM/SAED. The results indicated that LaPO4 was segregated at the grain boundaries of the composite coatings and the addition of LaPO4 into 8YSZ coating increased their CMAS reactivity, which led to the formation of planar reaction zone while the CMAS infiltration depth decreased from ∼658 μm to ∼119 μm. The CMAS infiltration depth of the composite coatings firstly increased with LaPO4 addition, reaching its maximum for the composite coating with 5 wt% LaPO4, and then showed a downtrend. For the composite coating with 20 wt% LaPO4, a dense apatite layer formed in the corrosion front, which inhibited CMAS penetration and resulted in the shallowest CMAS infiltration depth among the test samples.

Erosion wear of the multilayered high velocity oxy‐fuel ceramic coatings on aluminum alloy composite substrate

AbstractHigh velocity oxyfuel coatings have been sprayed on aluminium (Al) alloy composites substrate with varying coating thickness and tested for their wear behavior. The density and micro‐ hardness of the coatings found to increase with increase in coating thickness. The air erosion wear test has been conducted using quartz sand of size up to 75 μm as erodent. The steady state experiments indicate that the greatest specific erosion rate is at 60° and minimum at 30°. Due to the presence of interlayer, specific erosion rate decreases with the increase in the thickness of the coatings. Surface topography of the eroded samples indicate a decrease in surface roughness with increase in impact velocity. Thereafter, Taguchi (L16) orthogonal array has been utilized in order to optimize the input parameters. Analysis of variance has been applied to determine the contribution of individual control factors. The results from Taguchi experiments and analysis of variance find the order of dominance of control factors and their individual contribution as: velocity (47.31 %) > coating thickness (29.94 %) > angle (13.26 %) > erodent feed rate (7.65 %). Coatings have exhibited a semiductile wear behavior.

Effect of Aluminide Coating Thickness on High-Temperature Fatigue Response of MAR-M247 Nickel-Based Superalloy

Effect of Aluminide Coating Thickness on High-Temperature Fatigue Response of MAR-M247 Nickel-Based Superalloy

Study of optical characteristics of microdischarges in the micro-arc oxidation process

Micro-arc oxide coatings of aluminum alloy AD31 samples were formed in an electrolyte containing 2 g/l NaOH and 9 g/l Na2SiO3 for 2, 4, 8, 16 min in the anode and anode-cathode modes. During the processing, the forming curve, the time dependences of the charge passed through the galvanic cell, and the optical parameters of the microdischarges were measured using the optical synchronization method developed by the authors with subsequent image recognition. The thickness of the coatings was measured using a point autofocus probe surface texture measuring instrument Mitaka PF-60, the surface morphology was studied using a VEGA3 scanning electron microscope using SBH surface topography. The elemental composition of the coatings was determined using a scanning electron microscope JSM-6610LV. The analysis of the elemental composition and morphology of the surface revealed that the inner layer of synthesized coatings consists of Al2O3, the outer layer consists of Al2O3·SiO2 mullite, and the ratio of phases Al2O3 and mullite changes with changes in current density and oxidation mode. The formation of mullite is due to the presence of Na2SiO3 in the electrolyte. It is shown that with increasing processing time and current density, the thickness, roughness and porosity of coatings increase. The interrelation of the optical parameters of microdischarges with the morphology of the surface and the elemental composition of the formed coatings is substantiated; it is shown that the ratio of illuminated and non-illuminated sections of the sample surface by microdischarges can be used as a rough estimate of the ratio of electron and ion currents corresponding to microplasma and electrochemical processes. A mathematical model describing the dependence of the coating thickness on the oxidation time based on Faraday's laws for electrolysis and the results of measuring the optical parameters of microdischarges and the electrical parameters of the MAO process without taking into account microplasma processes that do not lead to an increase in the thickness of coatings is proposed. The error of adequacy of the proposed model does not exceed ±10 %. The results of the study can be used in the development of a digital twin of the micro-arc oxidation process.

NEW METHODOLOGIES FOR ASSESSING CAVITATION LOAD AND RESISTANCE OF STRUCTURAL MATERIALS AND PROTECTIVE COATINGS IN NUCLEAR POWER INDUSTRY. PART II. POLYFRACTIONAL APPROACH

A fractional approach to cavitation erosion process as proposed previously by one of the authors is explained. The polyfractional erosion process is considered as a superposition of a series of monofractional ones and described by a differential kinetic equation with a set of parameters constituting “the erosion resistance matrix”. The funda-mental methodological considerations are supplemented by describing the most typical applications including pre-diction of erosion of structural materials under given cavitation load, derivation of cavitation erosion fatigue charac-teristics, retrieval of effective erosive load basing on performance of reference materials. Finally, extending the methodology onto thin and thick protective coatings is proposed.

Thermal Behaviour of Hydrofugated Plaster Block Masonry with Variation of Coating Thickness

The objective of this research is to analyze the influence of ceramic coating, simulating the external side, and plaster with different thicknesses, simulating the internal side of a prototype of solid water-repellent gypsum block masonry, aiming to improve the thermal performance mainly in the settlement joints of the block. For this purpose, two specific test methods were used: thermal camera and infrared thermography. The temperature differences between the internal and external faces were analyzed by means of thermocouples connected in the middle of the prototype and the mapping of the temperature profile on the surface of the cladding. It was found that the addition of gypsum sheathing plus ceramic improves the thermal performance of the masonry system, observing that the variation of the thickness of the gypsum mortar provides a gain in thermal resistance, a reduction in thermal transmittance and an increase in thermal capacity.

Molecular dynamics study of the groove-forming mechanism of mechanically scratched grating multilayer aluminum films

For a long time, the forming quality of large area diffraction gratings is restricted by the one-time coating quality and uniformity of large thickness and large area aluminum films. Large thickness coatings, low accuracy of large depth grooves and diamond tool wear problems were the main reasons for the failure of the test to inscribe large area diffraction gratings. Therefore, the use of layered coating process can effectively ensure the uniformity and consistency of large-area and large-thickness grating blanks coated with aluminum film, and improve the high precision of large depth diffraction grating slot type. In order to reveal the mechanism of the groove-forming process of multilayer aluminum films, the microstructure and mechanical properties of different aluminum films were observed. In this article, the removal behavior and mechanism of nanomechanically scratched multilayer aluminum film materials are investigated using a molecular dynamics approach, and the characteristics of multilayer aluminum films scratched into grooves are analyzed in terms of surface morphology, scratching force, structural evolution, dislocation distribution, von Mises stress and shear strain. The results indicate that in the scratching simulation process, multilayer aluminum film has a higher number of removed atoms and a larger atomic displacement compared to single layer aluminum film, which is conducive to precise shape control of the groove. The average tangential force and normal force of multilayer aluminum film show a decreasing trend compared to single layer aluminum film, which helps to scratch grooves and reduce tool wear. The total length of the dislocation lines of the multilayer aluminum film is large, and the distribution area is large, which improves the precision of scratching the grooves. Therefore, an appropriate increase in the number of aluminum film layers has a precise control effect on the groove shape. This study has certain reference significance for analyzing the complex grooving deformation law of grating aluminum film, improving the diffraction efficiency of grating aluminum film, and further improving the manufacturing process of grating aluminum film.

Effects of TiAlN Coating Thickness on Machined Surface Roughness, Surface Residual Stresses, and Fatigue Life in Turning Inconel 718

The surface roughness and surface residual stresses are affected by the coating thickness of physical vapor deposition (PVD) TiAlN tools, which could alter the service performance of machined components. However, the relationships among the tool coating thickness, the machined surface roughness, the surface residual stress, and the fatigue life are still not sufficiently illustrated. In this research, PVD TiAlN coatings with several thicknesses of 1.6 μm, 2 μm, 2.5 μm, and 3 μm were deposited on carbide tools. Turning experiments using Inconel 718 were conducted with uncoated and various TiAlN tools under flood cooling conditions. The surface roughness could be improved with the selection of thin PVD TiAlN coating thicknesses of 1.6 μm and 2 μm compared to that of uncoated tools. The tensile residual stresses at the machined surface in the directions of cutting speed and feed rate linearly decreased by 148.67% and exponentially decreased by 92.24% when the TiAlN coating thickness was increased from 0 μm to 3 μm. The values of the low-cycle fatigue life of machined Inconel 718 linearly increased by 15.60% with the increase in TiAlN coating thickness from 0 μm to 3 μm, which was mainly due to the improvement of surface residual stresses. The results could provide guidance for the selection of suitable TiAlN coating thicknesses for wet machining Inconel 718 based on the part service conditions.

Morphological Seed Traits Predict Early Performance of Native Species to Pelletized Seed Enhancement Technologies.

Native seeds are a finite resource, and their inclusion in revegetation is vital for supporting restoration outcomes that are both effective and scalable. Pelletized seed enhancement technologies (SETs) offer a promising solution to improve seed use efficiency in ecological restoration. Yet, knowledge of how diverse suites of native species perform when pelletized is required to optimize the application of SETs to the many species and ecosystems where restoration is required. Using a greenhouse trial of 64 Australian plant species, we assessed species performance to pelleting by evaluating (1) overall species amenability to pelleting based on total emergence and survival and (2) how pelleting modifies the rate of emergence based on average time to emergence, emergence rate index, and time spread of emergence. We investigated the potential for using morphological seed traits (seed endosperm:seed ratio, seed length, seed area, and seed coat thickness) to predict performance outcomes, by identifying traits that may aid in the prediction of species amenability to pelleting and emergence speed when pelletized. We found that some species demonstrate high amenability to pelleting and that pelleting can modify the emergence rates for many species. This work advances our understanding of the applicability of SETs for diverse native species, demonstrating the application of such technologies for meeting ecological restoration goals.

Advancements in Dry Coating for Battery Electrodes: Scalable Extrusion Mixing for Control of Electrode Microstructure and Electrochemical Performance

Dry coating of battery electrodes is emerging as a promising alternative technology to the prevailing slurry coating and drying process widely adopted in the lithium-ion battery industry.1,2,3 To date, the most energy-intensive step in cell manufacturing is the drying of slurry-coated electrodes,1 and the adoption of dry coating aims to mitigate both the environmental impact and production costs associated with electrode production. Beyond environmental and economic concerns, producing higher mass-loading electrodes, a crucial aspect for increasing cell energy density, faces inherent challenges with the slurry-coating process: the drying of thick coatings often leads to issues such as electrode cracking and the formation of inhomogeneous electrode microstructures.Bühler and Empa have collaboratively developed and are in the process of scaling up a dry-coating manufacturing method.4 Our process centers around the extrusion mixing of electrode components, followed by calendering of the dry mixture to produce the final electrode and direct lamination onto a current collector. In this presentation, we showcase the adaptability of extrusion mixing in inducing shear fibrillation of polytetrafluoroethylene (PTFE) binder, crucial for achieving the desired electrode microstructures (see Figure 1a and 1b). Furthermore, we demonstrate the capability of our dry-coating technology to produce high-mass loading electrodes with areal capacities of 5 mAh cm-2 or more (see Figure 1c).The presentation encompasses a thorough characterization of dry-coated electrodes, including their microstructure and electrochemical performance in lab-scale batteries. Key aspects, such as rate capability and capacity retention, are evaluated. A comprehensive comparison with slurry-coated electrodes, fabricated using identical active electrode materials, mass fractions, and mass loading, reveals that our dry-coated electrodes exhibit comparable performance to their slurry-coated counterparts.5 The scalability of our dry-coating technology is underscored, highlighting the achievable throughputs necessary for gigafactory-scale production with a single extruder.

Study on preparation and anti-sand erosion performance of thick DLC coating combined with FCVA deposition and HVP technology

To address the compatibility issues between the hardness and thickness of DLC coatings and to improve the erosion resistance of engine blades, a thick DLC coating was prepared using a combination of filter cathode vacuum arc (FCVA) deposition technology and high voltage pulse (HVP) technology. The prepared thick DLC coating exhibits low residual stress (1.79 ± 0.087 GPa) and high C-sp3 content (70.13 %), with a thickness and hardness of 18.46 μm and 51.07 ± 0.23 GPa, respectively. The results of anti-sand erosion tests indicate that the mass loss rates of DLC coating at the erosion angles of 45° and 90° are 4.44 × 10−3 mg/g and 1.99 × 10−2 mg/g, respectively. The good erosion resistance of thick DLC coatings is attributed to the consumption of residual impact energy by carbon cluster structures, which prevents the generation and propagation of cracks. Therefore, the thick and super-hard DLC coatings can be prepared by combining FCVA deposition technique with HVP technique, which has great potential applications in the aerospace industry.

Analysis of Primary Coating Thickness Effects on Adhesion Strength in S355J2+N Steel Material

Analysis of Primary Coating Thickness Effects on Adhesion Strength in S355J2+N Steel Material