Thick Coatings Research Articles

Numerical Analysis of 3D Unilateral Quasi-static Contact: Effect of Coating Thickness and Mechanical Properties

In this study, a numerical model for unilateral quasi-static contact between a rigid sphere and an elastic coating has been developed. The contact problem was solved using a numerical procedure based on the FFT technique, considering various coatings with different thicknesses and mechanical properties, implemented through a Matlab code. The model calculates the contact surface deformation and pressure field through a double iteration process. The first iteration solves the contact problem for a given indenter penetration, while the second iteration refines this penetration by minimizing the difference between the fixed and calculated loads. To achieve this, influence coefficients are derived from the elasto-static equations using the Papkovich-Neuber potentials. The study discusses the influence of coating thickness and friction coefficient value on the tribological behavior of the coating. The results indicate that contact pressure increases (ranging from 1.9 to 2.5) as the coating becomes thicker or more rigid (0.02 mm to 0.2 mm). Additionally, the tribological behavior of the coated surface is affected by the coating's thickness, hardness, and friction coefficient value. Importantly, this model demonstrates versatility by being applicable to both smooth and rough surfaces.

Study of resin coating adhesion on GFRP laminate surfaces after UV degradation

This paper describes research on the effect of UV radiation on the surface of a GFRP (Glass Fiber Reinforced Polymer) laminate in the context of increasing the adhesion between the laminate and polymer resin coatings. GFRP composite samples were prepared using the hand lay-up method. The samples were then exposed to various types of ultraviolet radiation (UVA, UVB, UVC) for 1000 h, with surface roughness measurements every 100 h. The flexural strength of laminates after photoaging was tested, which showed an increase in the strength of aged laminates compared to the reference sample by approximately 5–10 %. Coatings of various thicknesses were applied to the surface of the aged laminates and their adhesion to the substrate material was tested using the mandrel bending method alongside the cross-cut technique. The greatest change in surface roughness was observed on the sample exposed to UVC radiation, where the roughness increased approximately twice in relation to the reference sample. Coating adhesion tests have additionally shown that degradation under the influence of UVC has a positive effect on the adhesion of coatings to the laminate.

Interface stiffness identification of rough and weak bonded interface using developed ultrasonic reflection phase derivative spectrum

The thickness and interface roughness of coatings both affect the interface bonded quality. Existed ultrasonic testing methods based on traditional phase screen approximation or spring model assumption are difficult to simultaneously identify the interface roughness and stiffness of coating. This paper, a new method for integrated identifying coating thickness, interface roughness, and interface stiffness using developed ultrasonic reflection phase derivative spectrum (URPDS) is proposed. A phase-screen-approximated spring-model (PSASM) for ultrasound vertically propagating into rough and weak bonded interface is constructed. On basis of PSASM, a URPDS of coating/substrate structure is developed for identifying the interface stiffness and other parameters of coated parts. Cross-correlation analysis is used to eliminate the phase deviation of URPDS introduced by reference signal and initial phase of tested signal. Sensitivity analysis is used to determine the high-sensitivity regions of URPDS to interface roughness and interface stiffness. Genetic algorithm optimization is used to achieve integrated identification of coating thickness, interface roughness, and interface stiffness. The rationality of PSASM is verified through numerical simulation using a series of coating/substrate models with rough and weak bonded interface, and the relationship between the high-sensitivity regions and the high-precision measurement ranges of interface roughness Rq and interface stiffness Kn is clarified. Ultrasonic experiments are implemented on Nickel-coating samples and coated parts using plane wave probe. The coating thickness, interface roughness, and interface stiffness could be identified accurately, which shows that the proposed URPDS method can identify the interface stiffness of rough contacted dissimilar media or coated parts with rough interface.

Response of variation of electrical control parameters to coatings prepared in organo-silicon electrolyte by plasma electrolytic oxidation

This study aims to explore the influence of control parameters from the perspective of the amorphous ceramic coating formation process. Three preparation processes were preferred based on the thickness, appearance and corrosion resistance of the coatings by orthogonal experiment. The surface morphology, cross-sectional structure, phase composition and micro-hardness of PEO coatings were examined using scanning electron microscopy (SEM)/Energy dispersive X-ray spectroscopy (EDS), X-ray diffractometry (XRD) and hardness measurement techniques. Findings indicate that voltage exerts the most significant impact on coating thickness and appearance, whereas the influence of other parameters becomes more pronounced as the voltage increases. Three amorphous ceramic coatings prepared in 20 min with thicknesses of 27.4 μm, 83.2 μm and 193.3 μm increased the surface hardness of 6061 aluminium alloy by 6–8 times, and decreased the corrosion current density of 6061 aluminium alloy by 3 orders of magnitude in 1 mol L−1 HCl solution. Moreover, the thickening of the coating primarily occurs within a few minutes after the voltage reaches its peak, and high frequency and low duty ratio are prerequisites for better appearance under higher voltage conditions.

Electrophysical and thermoelectric properties and crystal structure of the formed Mn4Si7 thin vacuum coatings

The necessary information on the formation of high manganese silicide (Mn4Si7) coating by magnetron sputtering method is presented in this work. The technology and basic modes of creating the necessary targets for a magnetron sputtering device are presented. Targets were created by adding silicon and manganese powders in the required amount and heating them under vacuum conditions at high temperature and pressure. Thin silicide films (thin coatings) of different thicknesses were formed on the surface of silicon dioxide from the produced targets using the method of magnetron sputtering. The electrophysical and thermoelectric properties of the produced films were studied using physical and optical methods.Due to the change in the structure of the coatings during subsequent heat treatment, the Seebeck coefficient noticeably increases.

Examination of nonideal film growth in batch atomic layer deposition for plasma-resistant coatings

Atomic layer deposition (ALD) can be used to fabricate protective coatings including moisture barrier layers for organic light emitting diodes, anticorrosion layers for photoelectrodes, and plasma-resistant coating for semiconductor manufacturing equipment, which necessitates the deposition of large and thick ALD films via batch ALD. However, batch ALD for the fabrication of large-area and thick coatings exhibits nonideal film growth, a phenomenon that cannot solely be explained by transient concentration distribution within the deposition chamber. This paper describes the application of precursor “exposure” (in the unit of Langmuir, or Pa s), defined as the integral of concentration over time, as a metric to assess the growth per cycle (GPC) distribution under nonideal ALD conditions, demonstrating that the local GPC correlates well with the cumulative precursor exposure at that site. Consequently, this measure can effectively predict the nonuniformity (NU) distribution of film thickness and facilitate the determination of optimal operating conditions that ensure maximal uniformity of exposure. Under this condition, the intrafilm NU of ALD-grown Al2O3 film (nominal thickness 300 nm) was reduced to 1.2%, and the interfilm NU is diminished to as low as 3.3%. These values represent reductions of 40% and 45%, respectively, compared to the NU levels observed under nonideal conditions (insufficient trimethylaluminum, TMA exposure downstream). The plasma etch rate of ALD-deposited films is merely 4.3 nm/min, representing a reduction of one-half compared to films deposited under nonideal conditions (9.8 nm/min) with overload TMA exposure downstream leading to chemical vapor deposition-like reactions.

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.

Clean and durable thick nanodiamond composite hard coating deposited on cemented carbide towards sustainable machining: Eco-friendly fabrication, characterization, and 3-E analysis

This research explores a sustainable approach for fabricating high-performance nanodiamond composite (NDC) hard coatings for dry machining. Aiming to address limitations in conventional coatings, such as environmental concerns, restricted film thickness, and compromised performance. The study utilizes Coaxial Arc Plasma Deposition (CAPD), a clean and efficient technique, to deposit thick (10 μm) NDC films directly on WC−Co substrates without chemical etching. Compared to traditional Chemical Vapor Deposition (CVD), CAPD offers significant advantages: lower temperature deposition, faster growth rate, and precise control over film thickness and morphology. The resulting NDC films boast exceptional durability due to their unique nanostructure, diamond nanocrystallites embedded in an amorphous carbon matrix. The addition of Al-interlayers (100–500 nm thickness) optimizes film properties. The optimal interlayer at 100 nm thickness not only mitigates the catalytic effects of Co but also enhances film hardness (50.4–58 GPa), Young's modulus (516–613.75 GPa), and adhesion (13–18.5 N) compared to films without an interlayer. Notably, the 100 nm Al-interlayer triples the deposition rate to 3.3 μm/h, achieving the desired thickness for effective hard coatings. The high density of grain boundaries within the films allows for exceptional stress release, enabling this increased thickness. Furthermore, these grain boundaries and the graphitic phase contribute to the film's superior tribological performance – a low coefficient of friction (0.1) and minimal wear rate (1.5 × 10⁻7 mm³/N⋅m) under dry machining conditions. These findings demonstrate the immense potential of CAPD-deposited NDC films as a sustainable alternative for advanced cutting tools, promoting environmental responsibility, economic viability, and energy efficiency.

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.

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.