Adhesion Strength Of Coatings Research Articles

Pulsed Magnetron Sputtering of Ceramic SHS Targets as a Promising Technique for Deposition of Multifunctional Coatings

The processes of the pulsed magnetron sputtering (PMS) of multicomponent ceramic targets are studied upon deposition of functional coatings of various purposes. The regularities of changes in the structural characteristics, as well as mechanical and tribological properties, under increasing magnetron power frequency are studied. Summarizing the results obtained using the PMS technology upon the deposition of coatings using multicomponent SHS cathodes, the following conclusions can be drawn. a) The structure of coatings. Pulsed sputtering leads to the development of a denser and, at the same time, more defective structure with a high level of internal stresses and roughness. The effect of the pulsed mode on the grain size depends on the sputtering type and configuration of magnetic fields. For reaction sputtering, structural refinement is observed in some cases. The effect of increasing the thickness of reaction coatings due to the commencement of interaction between atoms sputtered from the target and nitrogen atoms at precipitation and minimization of target surface poisoning is found. b) Coating properties. The effect of a pulsed mode on the adhesion strength of coatings is reduced to its decrease. Dependences of hardness and other mechanical properties on the frequency of the pulse power have an extreme character with a maximum at 50 kHz. The use of low frequencies (50–150 kHz) leads to a decrease in the friction factor. At the transition to the pulsed mode, the friction factor stabilizes during the test and, in most cases, wear resistance increases.

Determining the Adhesive Strength of Thin Hard Coatings

A method is proposed for determining the adhesive strength of thin coatings, taking account of their thickness. The method is used to determine the adhesive strength of some coatings, taking account of the elasticity of the base. It proves effective for coatings of practically any thickness.

Estimation of residual stress level in plasma coatings of increased thickness

Regulation of the thermal and stress state of the “coating-base” system is an important step of the coatings quality management and is carried out by changing the thermal power of the plasma jet per unit of the sprayed surface by controlling the movement velocity of the plasma torch and the sprayed material flow rate. (Research purpose) The research purpose is development of a mathematical model that describes the process of layer-by-layer coatings formation and the change in the thermal state of the coating-base system during plasma spraying. (Materials and methods) We have used finite differences, finite elements and marching for solving the thermal and strength problems in internal stresses determining. We have used a technique for determining thermal fields, considering the dependence of thermal-physical and mechanical properties of the coating and base materials on temperature, the occurrence of plastic deformations and stress relaxation. A mathematical model has been designed for calculating a thermal field with a moving boundary considering the nonlinear nature of coating growth during layer-by-layer deposition and the dependence on the thermophysical properties of the coating-base system materials. We have substantiated the method that allows eliminating the existing shortcomings of traditional technologies for design and experimental studies of the thermal and stress state of the coating-base system, as well as automatization of the process of solving the numerical model and increasing the efficiency of the entire research cycle. (Results and discussion) It was found that when the flow rate of the sprayed material is changed from 0.1 to 1.0 grams per second and the plasma torch travel velocity is from 10 to 350 millimeters per second, the residual stresses in PG-19M-01 coatings on steel change their sign and can be both compressive and tensile. Varying the coating conditions allows reducing the level of residual stresses by 3-5 times. The article shows that a decrease in the level of residual stresses corresponds to an increase in the coating adhesion strength at a constant mass average temperature of the particles during the deposition process and is achieved by controlling the sprayed material flow rate and the plasma torch velocity, pre-heating the substrate and cooling. (Conclusion) It was found that the use of the proposed model makes it possible to evaluate the effect of the parameters of the spraying process (plasma torch travel velocity, spray material consumption, thermal state of the substrate before spraying, cooling conditions during spraying) on the residual stresses level.

Adhesion Enhancement of Poly (acrylamide -co- Acrylic Acid)/ Polyethylene Glycol anti-Biofouling Coating using Fly Ash based Geopolymer

Hydrogel has been used as an alternative to replace biocide-based paint in preventing biofouling. However, hydrogel has low adhesion on metallic substrate, hindering its application for coating. Therefore, the aim of this project is to enhance the adhesion strength and anti-biofouling properties of the poly(acrylamide-co-acrylic acid)/polyethylene-glycol hydrogel, poly(AAm-co-AAc/EG) coating via the incorporation of fly ash-based geopolymer that range from 0.5 wt% to 2.5 wt%. The hydrogel coating was synthesised via free radical polymerisation with the aid of N,N-methylenebisacrylamide (MBA) as the crosslinker, and ammonium persulfate (APS) as the initiator. The Fourier transform infrared (FTIR) spectra of the hybrid hydrogel had proved the presence of geopolymer with the availability of significant peaks at 3,294 cm-1 (N-H bond), 2,946 cm-1 (O-H bond), 1,545 cm-1 (C-O-C bond) and 1,113 cm-1 (Si-O-Si or Al-O-Si bond). The average swelling capacity of the hybrid hydrogel coating in distilled water (up to 50,000%) was significantly higher than in artificial seawater (up to 5,000%) due to osmotic pressure difference. The anti-biofouling performance test by using algae (Chlorella vulgaris sp.) suspension showed that the incorporation of 2.0 wt% geopolymer into hybrid hydrogel coating had successfully reduced the algae attachment on the substrate by 92% as compared to the control sample. The adhesion strength of all hydrogel coatings was investigated by using the pull-off adhesion test in accordance to ASTM D4541. The incorporation of 2.0 wt% geopolymer into hydrogel matrices demonstrated an increment of 58% in adhesion strength on steel plate as compared to neat hydrogel. The results showed that geopolymer has the potential to improve the anti-biofouling and adhesion strength of hydrogel coating.

Effect of micro-blasting on the tribological properties of TiN/MT-TiCN/Al2O3/TiCNO coatings deposited by CVD

The effect of micro-blasting on the tribological properties of TiN/MT-TiCN/Al2O3/TiCNO coatings was studied. The multilayer coatings were deposited on cemented carbides by chemical vapor deposition. The microstructure, mechanical and tribological properties were investigated using X-ray diffraction, scanning electron microscopy (SEM), nano-mechanical testing system, scratch tester and reciprocating tribometer. The results show that micro-blasting significantly reduces the surface roughness and converts the residual tensile stress of Ti(C,N,O) top-layer and Al2O3 layer into compressive stress. Affected by the residual compressive stress, the hardness and adhesion strength are increased. More importantly, the friction coefficient is decreased attributed to the decreased surface roughness and improved hardness. Also, the wear resistance of micro-blasted TiN/MT-TiCN/Al2O3/TiCNO is superior due to higher hardness of Ti(C,N,O) top-layer, Al2O3 layer and adhesion strength of coatings. Especially for the total sliding time of 2 h, the wear volume and wear rate of micro-blasted coatings are 69.4% of as-deposited coatings, because micro-blasting helps to increase the adhesion strength and micro-cracking resistance, which play important roles in the improvement of wear resistance. Micro-blasting has a positive effect on the friction and wear properties of TiN/MT-TiCN/Al2O3/TiCNO multilayer coatings since the adverse impact of top-layer thinning is offset.

Automated evaluation of Rockwell adhesion tests for PVD coatings using convolutional neural networks

An automated method for the classification of the adhesion strength of thin PVD coatings applied on hardened steel substrates is presented in this study using deep neural networks. For the determination of the adhesion strength Rockwell-indentation tests were carried out according to VDI 3198. For this approach, pre-trained convolutional neural networks are adapted to classify microscopic images into the expected adhesion classes HF 1 to HF 6 using transfer learning with a dataset of 1650 already evaluated indentation images. The classification performance of the Matlab implemented network models AlexNet, GoogLeNet and inception-v3 is compared with test and verification images of Rockwell indentations. The inception-v3 network shows good accuracy for polished (roughness Sa < 20 nm), hardened steel substrates with deposited thin coatings of a thickness up to 5 μm. The classifications of the implemented models exhibit an agreement of approximately 85–90% compared to human assessment. The evaluation is robust against disturbance variables such as different exposure times, brightness, image contrasting and magnifications. Different image capture devices can be used with no effect on the classification. The networks show promising results for automated industrial applications, such as in-line adhesion control in coating processes, as they do not require human operator support.

Investigation of the Influence of Kinematic and Geometric Parameters of the Thermo- Sprayer Location on the Adhesion Strength of Anti-Friction Coating

The article presents the results of the influence of the kinematic and geometric parameters of the thermos-sprayer location on the adhesion strength of the anti-friction coating. A mathematical apparatus for calculating the inertia forces acting on an anti-friction coating particle is proposed. The results of a number of experimental studies confirming the convergence of theoretical positions are presented. As a result, dependencies have been revealed that make it possible to predict the bond strength of the anti-friction coating with the steel base during gas-flame spraying.

Enhancing the adhesion strength of polyurethane coatings by dispersing layered silicates via sonication and high-shear mixing method

Low adhesion strength of polyurethane coating to a steel substrate is often attributed to poor steel preparation. However, the ratio of diisocyanate/polyol and dispersion of fillers within a polyurethane coating matrix influence the adhesion strength, optical and corrosion resistance properties. Poor dispersion of nano-fillers in a polymer coating matrix can lead to low adhesion strength, because close packing of nanoparticles often hides the hydroxyl groups required to form polar–polar bonds with the steel surface. This study combines sonication and high-shear mixing methods with shorter mixing times to prepare polyurethane nanocomposite coatings with various clay concentrations while keeping the ratio of diisocyanate/polyol constant. Fourier-transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM) and X-ray diffraction, thermogravimetric analysis and pull-off are used to characterize polyurethane nanocomposite coatings. FTIR results confirm that sonication and high-shear mixing successfully prepare polyurethane-based coatings. TEM shows uniformly dispersed clay particles in polyurethane matrices. The adhesion strength improved on addition of 1–5 wt% C30B organoclay, with the highest improvement (34.4%) at 3 wt% loading. The corrosion resistance of polyurethane coatings was improved by the incorporation of organoclays into their matrices. Onset degradation temperature is also delayed by 4.1–8.5% as the clay concentration increased from 1 to 5 wt%.

Improving adhesive strength of WC-CoCr coating with novel bimodal roughening substrate: Finite element modeling

The durability of a coating-substrate system is mainly determined by its adhesion strength. However, a major challenge is to effectively evaluate the adhesive effect after design, as measuring the adhesion strength of complex composite coatings is difficult. In this work, a bi-roughened surface of substrate was designed and its effects on the adhesive strength of WC-CoCr coatings were explored by simulation. Initially, a finite element model was established to simulate the substrate-coating system with bi-roughening (sub-roughness and sub-roughening angles) interface. In the case of monomodal Ra 7.5 μm, the adhesive strength was predicted to be only 68 MPa. While, the designed sub-roughening of Ra 0.8 μm enhanced the value to nearly 80 MPa. Moreover, the adhesive strength is further improved to above 100 MPa by tailoring the sub-roughening angle to 60°. The residual stresses along interfacial region decrease significantly for bi-roughening design, which can be responsible for enhanced adhesive strength. Additionally, individual crack growth occurs in almost every bi-roughening, and does not connect with the main crack, which result in a proportional increase in apparent interfacial shear strength. Briefly, adhesion strength is considerably improved for the bi-roughening design, which is beneficial for durability of the coatings during service.

Formation of film antifriction coatings on the friction surfaces of machine parts

The article presents a study of the adhesion strength of film anti-friction coatings. The process of a film anti-friction coating formation is described. An experiment to determine the adhesion strength of a film anti-friction coating is considered. In the course of the experiment, a number of samples of different roughness were used on which an anti-friction coating was applied. The thickness of the coating was controlled by a thickness gauge. Conducted a qualitative assessment of the adhesive strength of the coating with the base metal. Conclusions about the strength of adhesion, its dependence on surface roughness and initial surface treatment are made.

Surface Microstructuring of Steel Components for CVD Diamond Coating by Ultrasonic Vibration Superimposed Face Milling using Tailored Tools

Diamond coatings applied by chemical vapor deposition (CVD) provide extraordinary properties concerning hardness and wear resistance, which enables an increase of the performance or lifetime of highly stressed components. In particular, the combination of steel substrates and diamond coatings allows for numerous applications in several sectors of industry. However, there are significant challenges considering the coating adhesion strength. For example, the mismatch concerning the thermal expansion of steel and diamond commonly leads to a delamination of the coating. Thus, a suitable pre-treatment of the substrate surface is compulsory.With the aim of improving CVD diamond coating adhesion, ultrasonic vibration superimposed machining (UVSM) is applied when doing face milling on steel X46Cr13 specimens. The vibration direction is parallel to the tool axis and perpendicular to the feed direction. The tool wear and the surface microstructure are determined by 3D laser scanning microscopy.The investigations show, that predefined microstructuring of the substrate surface by UVSM contributes to an enhancement of the CVD diamond coating adhesion, especially regarding coatings with a thickness up to 10 µm. This can be referred to a better distribution or a reduction of thermally induced residual stresses in the diamond layer. However, a reliable generation of deterministic microstructures by UVSM significantly depends on the wear behavior of the tool. Uncoated cemented carbide grades exhibit considerable deficits reflecting in rapid tool wear. Therefore, adapted tool coatings are experimentally investigated, which result in an increase of the tool life and a reduction of the geometrical deviations of the microstructures. With an appropriate system of surface microstructure and coating, for example for tribological applications substantial improvements in terms of wear resistance and coefficient of friction are expected.

Adhesion strength of protective and decorative coatings depending on the porosity of the cement substrate

Information provided about long-term bonding strength protective decorative coatings. A method is proposed for assessing the long- term bonding strength of coatings. The method consists in determining the bonding strength before testing and after t hours of testing. The dependence of the long-term bonding strength on the porosity of the cement substrate has been established. With an increase in the surface porosity of the substrate, observed a decrease in the time of maintaining the adhesive contact “coating-substrate». The aging process of coatings is considered from the position accumulation of damage, taking into account the hereditary factor. The influence of the hereditary factor on the kinetics of damage accumulation was established. It is shown that the dependence of the operating time on the level of damage accumulation can be approximated by an exponential dependence. The values of the activation energy of adhesive destruction of coatings are calculated.

Зависимость между параметрами вязкости и прочности сцепления газотермических покрытий деталей лесных машин

Зависимость между параметрами вязкости и прочности сцепления газотермических покрытий деталей лесных машин

EFFECT OF ARTIFICIAL WEATHERING AND TEMPERATURE CYCLING ON THE ADHESION STRENGTH OF WATERBORNE ACRYLATE COATING SYSTEMS USED FOR WOODEN WINDOWS

ABSTRACTThe adhesion of coatings to wood is important for their long-term performance. In this study, the adhesion strength of water-based acrylate coatings used for wooden windows after exposure to artificial weathering (AW) and temperature cycling (TC) was investigated. The analysis of the adhesion quality of coatings was performed via a pull-off test and failure characteristics. The 3-layered and 4-layered white and brown acrylate dispersions from six different producers were compared and the effect of coating thickness on adhesion strength was investigated. The adhesion strength values proved to be very variable. After AW, the adhesion strength and its variability increased for all the samples. TC had no statistically significant effect on the adhesion strength values. White coating systems were initially characterized by lower adhesion strength, but after AW and TC, they reached higher adhesion strength values than brown ones. The overall highest adhesion after AW and TC was recorded for the coatings based on alkyd-acrylate hybrid basis (Producer 3), while the lowest adhesion variability after AW was measured for one type of tested acrylate coating (Producer 4). The effect of different layering on adhesion strength was not demonstrated in this study.

Corrosion Resistance and Cathodic Disbondment of Epoxy Coating Applied on Zinc Phosphate Conversion Coating Containing Different Amounts of Cobalt Ions

In this study, the influence of phosphate surface pretreatment containing a cobalt ion additive on the anti-corrosion features of epoxy coating was investigated. Phosphate conversion coating (PCC) specimens were prepared. Then the epoxy coating was electrostatically sprayed on the phosphated substrate. The surface morphology and the composition of a zinc phosphate conversion coating with a cobalt ion additive were studied by scanning electron microscopy and X-ray diffraction, respectively. Also, the corrosion protection properties of specimens were studied by the polarization potentiodynamic test in 3.5% NaCl solution. Protective performance of double-layer coatings was studied using electrochemical impedance spectroscopy during 30 days in the mentioned solution. In addition, the impact of phosphate chemical treatment on increasing the adhesion strength of the powder coating was studied using the pull-off adhesion test and cathodic disbodnment test in the same solution. As a result, it was found that the corrosion resistance of PCC containing a cobalt additive enhanced significantly and that the PCC containing 3 g/L Co is less porous than other coatings. Also, the protection properties, adhesion strength, and cathodic disbondment resistance of the double-layer coatings with phosphate pretreatment containing 3 g/L Co increased significantly.

Investigation and prediction of adhesion strength of plasma coatings by mathematical modeling of deposition parameters

In this paper, studies were conducted in the field of adhesive strength of plasma coatings and the surface of the part. The propagation of a crack front in a plasma coating material with composite inclusions is simulated. It was proposed to consider the possibility of introducing into the composition of the material sputtering additional composite inclusions that have a greater plasticity and a size greater than the size of the particles in the coating.

Comparison of Some Physical and Mechanical Properties of Waterborne Acrylic Coating Systems Containing Commercial UV Absorbers and Tree Bark Extracts

Aim of study: The aim of this study was to compare solid content, dry film thickness, and adhesion strength of different tree bark extract based and a commercial UV absorber.&#x0D; Materials and methods: Waterborne acrylic-based coating systems containing 5 different tree bark extracts (maritime pine, Calabrian pine, black pine, alder, fir) and a commercial UV absorber (Tinuvin 400 DW) were applied to 2 different wood species; Scots pine (Pinus sylvestris L.) and beech (Fagus orientalis L.). The dry-film thicknesses of the coatings were measured with light microscopy. The adhesion strength of the coatings was determined to investigate the bonding ability of the coatings with wood surfaces. The solid contents of the coatings were also determined.&#x0D; Main results: Permeability is an important parameter for dry-film thickness and adhesion strength. Wood species also influenced the dry-film thickness as well as adhesion strength. The dry-film thicknesses of the coatings containing bark extracts were higher than those with commercial UV absorbers. Similarly, the solid content of the coating containing maritime pine bark extract was found to be the highest.&#x0D; Highlights: The dry-film thickness and adhesion strength of waterborne acrylic coatings on wood substrate seem to be affected by addition of tree bark extracts.

Investigation of mechanical properties and oxidation resistance of CVD TiB2 ceramic coating on molybdenum

TiB2 anti-oxidation ceramic coatings were successfully synthesised on a Mo substrate by using chemical vapor deposition (CVD). A scratch test was performed to measure the adhesion strength of the TiB2 ceramic coatings to the Mo substrate. The results indicated good adhesion between the two materials; the adhesion strength was 125mN. Furthermore, high-temperature oxidation tests indicated that the CVD TiB2 ceramic coating protected the Mo substrate against oxidation up to 900℃. Isothermal oxidation experiments revealed that the Mo substrate covered with a 13-μm-thick TiB2 ceramic coating was protected against oxidation for a duration of 5h. The oxidation kinetics followed a parabolic law for the first 2.5h and a linear law in the next 2.5h.

ИССЛЕДОВАНИЕ АДГЕЗИОННОЙ ПРОЧНОСТИ ПЛЕНОЧНЫХ АНТИФРИКЦИОННЫХ ПОКРЫТИЙ

The paper is dedicated to the investigation of adhesion strength in film coatings. The goal of the work is a qualitative estimate of the strength of film antifriction coatings applied on friction units of machines. The topicality is grounded by the fact that the friction decrease on surfaces in units ensures the increase of life, power effectiveness and reliability of machinery. &#x0D; Most of the works are dedicated to the study of manufacturing films, their phase composition, structure, stress-strain properties, whereas in the material offered the adhesion properties of film antifriction coating are emphasized, which is a sufficient novelty. &#x0D; During the investigations of the adhesion strength of antifriction film coatings there was used a method of a normal detachment. To carry out comparative tests there were prepared four groups of different antifriction coatings. For each coating under testing there were prepared five samples which were loaded with the smooth increase of a breaking tension. &#x0D; Therefore there are obtained experimental dependences of normal stresses (σ) upon relative elongation (ε), which allow using values obtained for surfaces coated with antifriction film coatings with different areas. Upon completion of coating tests both parts of the samples tested were subjected to visual analysis. In the course of the analysis a character of destruction was defined. As a result of the theoretical and experimental investigations carried out there were drawn conclusions describing a qualitative and quantitative estimate of the adhesion strength of antifriction film coating.

Experimental evaluation of interfacial adhesion strength of cold sprayed Ti-6Al-4V thick coatings using an adhesive-free test method

Cold spray (CS) is a rapidly growing solid-state additive material deposition technique often used for repair of high-value metallic components. This study aims at evaluating the interfacial adhesion strength of cold sprayed Ti-6Al-4V (Ti-64) coatings deposited onto Ti-64 substrates for repair applications. An adhesive-free test method, referred as modified Collar-Pin Pull-off Test was developed based on Sharivker's (1967) original design, in order to overcome the limitations of existing test approaches (both adhesive-based and adhesive-free). This method was designed to allow measurement of adhesion strength of high strength coatings such as CS Ti-64, where adhesion strength is higher than 70–90 MPa. A parametric study was performed to assess the effect of coating thickness, scanning speed, track spacing, toolpath pattern, and substrate surface preparation on the coating adhesion strength. A finite element model was also used to evaluate the stress distribution during the pull-off test, and to check the validity of the proposed test method. The proposed adhesive-free test method was found to be capable of measuring coatings with adhesion strengths beyond the upper limit of conventional adhesive-based methods such as ASTM C633. Among the investigated cases, the highest value of coating adhesion strength was measured around 122 MPa, in the case of CS Ti-64 deposited on ground Ti-64 substrates.