Search

A three-cathode arc-based evaporation system has been used to obtain vacuum ion-plasma high-entropy CrTiZrNbHf coatings. The statistically averaged concentration of components in the coating corresponds to Cr0.30Ti0.35Zr0.25Nb0.08Hf0.01. The kinetics of the coating deposition and the process of its structure self-organization have been studied by constructing a diagram of the Movchan–Demchishin–Thornton structure zone. Technological parameters such as the substrate temperature, vacuum chamber pressure, coating deposition rate, ion current density, bias voltage, etc., were combined into the form calculated. It is shown that, for the CrTiZrNbHf system under study, the critical value of the Ebi parameter amounts to about100 MJ/cm3. Exceeding this threshold leads to degeneration of the coating structure in the form of a nuclei-like or droplet-like morphology. [ABSTRACT FROM AUTHOR]

A systematic study is performed on the development of hot-dip galvanized coatings on a Mn-containing high-strength steel sheet by varying the dew point (− 50, − 10, and + 10 °C) during inter-critical annealing of the steel strip at 800 °C. It also studies the effect of dew point on the corrosion behavior of the coatings in freely aerated 3.5 wt% NaCl solution. The reducing gas atmosphere consists of 95% N2 and 5% H2, where inter-critical annealing is carried out. Surface oxidation of the steel has a strong effect on the development of sound coating. A defect-free adherent galvanized coating is obtained on the annealed steel surface at a fixed dew point of + 10 °C, and it is attributed to the fine and continuous compact Fe-Al crystals compared to galvanized coatings produced at other dew points as well as the highest atomically dense (0002) basal plane. This also leads to the lowest corrosion rate (~ 0.164 mm y−1, where mm and y stand for millimeter and year, respectively) of the galvanized coating produced at a dew point of + 10 °C when compared with galvanized coatings produced at dew points of − 50 °C (~ 0.279 mm y−1) and − 10 °C (~ 0.259 mm y−1). The lowest corrosion rate of the galvanized specimen developed at + 10 °C dew point can be attributed to the uniform and defect-free coating surface, together with the dominance of the more atomically dense (0002) basal plane. [ABSTRACT FROM AUTHOR]

A relatively small change in oxide content and microstructure in MCrAlY coatings (M = Co, Ni) can affect the functionality of the coating for oxidation protection or as a bond coat. The objective of this study is to fabricate a CoNiCrAlY coating with low porosity and low oxide content. The high velocity air-fuel (HVAF) process, with its relatively low process temperature, is particularly suitable for the deposition of spray materials that are susceptible to oxidation or degradation at high temperature. A CFD simulation model of HVAF process is developed to determine the process parameters for fabricating CoNiCrAlY coating. The simulation results are validated by particle diagnostics, thereby establishing a comprehensive understanding of the underlying process. To assess the coating microstructure, XRD and EDS analyses as well as observation of cross sections of the coatings are conducted. The results highlight the influence of various factors, such as the variation of carrier gas and particle size distribution, on the quality of the coatings. Consequently, the utilization of simulation-based process parameter development is well supported by the coating fabrications, offering valuable insights into the processes prior to implementation. [ABSTRACT FROM AUTHOR]

Cold spraying (CS) of high-strength materials, e.g., Inconel®625 is still challenging due to the limited material deformability and thus high critical velocities for achieving bonding. Further fine-tuning and optimization of cold spray process parameters are required, to reach higher particle impact velocities and temperatures, while avoiding nozzle clogging. Only then, sufficiently high amounts of well-bonded particle–substrate and particle–particle interfaces can be achieved, assuring high cohesive strength and minimum amounts of porosities. In this study, Inconel®625 powder was cold sprayed on carbon steel substrates, using N2 as propellant gas under different spray parameter sets and different powder sizes for a systematic evaluation. Coating microstructure, porosity, electrical conductivity, hardness, cohesive strength, and residual stress were characterized in as-sprayed condition. Increasing the process gas temperature or pressure leads to low coating porosity of less than 1% and higher electrical conductivity. The as-sprayed coatings show microstructures with highly deformed particles. X-ray diffraction reveals that powder and deposits are present as γ-solid-solution phase without any precipitations. The deposits show high microhardness and compressive residual stresses, which is attributed to work hardening and peening effects. The optimized deposits reach almost bulk material properties and are thus well suited for industrial applications. [ABSTRACT FROM AUTHOR]

One of the options for solving the scientific and applied problem of the predicted formation of ion-plasma coating tribological characteristics is presented. The problem is solved by creating and analyzing a carbon coating database. The object of research in this work is ion-plasma diamond-like coatings (DLCs) deposited on a steel substrate. It is shown that the use of nitrogen instead of hydrogen to stabilize carbon coatings not only ensures stable thicknesses of DLCs at the level of 1.0–1.5 μm, but also serves as an important and convenient technological parameter for regulating the tribological coating characteristics during deposition. Based on the predicted and experimental values of friction coefficient μ and data on sample path length L, the intervals of optimal values of technological parameters %N and λ are determined. The studied ion-plasma DLCs, obtained according to the established optimal application modes, can be recommended for application under friction conditions equivalent to the tribological tests carried out at friction load F ≈ 10 N. [ABSTRACT FROM AUTHOR]

For studying the deposition behaviour of dual-carbides cermet particles on coating microstructure and properties，the surface morphology and cross-sectional microstructure of the original powder and the flat particle on the low-carbide steel substrate were analyzed，and the microstructure，phase constitution and properties of HVOF sprayed micro-nano WC-Cr3C2-CoNi coating were investigated systemically.Results showed that the particles deposited on the substrate showed a caky shape with smooth and convex surface，radial sputtering streaks appeared around the particles，and the thickness of flat particles was much smaller than their radial dimensions.In addition，the section microstructure of the coating presented certain lamellar characteristics，and the interfaces between flat particles，hard phase and bond phase，flat particle and substrate and different hard phases bonded well.The coating had the main phase of WC，some decarburized phases，and the amorphous phase of Cr2O5.Moreover，the microhardness，elastic modulus，fracture toughness，adhesive strength and wear weight loss of the coating were (13.19±0.52) GPa，(145.17±3.89) GPa，(2.59±0.64) MPa·m1/2，(38.41±0.51) MPa and (6.08±0.68) mg respectively.Compared to WC-Co12 coating，the decomposition of WC and the decarburized phases decreased significantly in the HVOF sprayed micro-nano WC-Cr3C2-CoNi coating and the coating’s mechanical properties were obviously improved.

In this work, the composition of the zinc–aluminum–magnesium alloy coating was designed to have a fixed aluminum–magnesium ratio of 1:1, while the content of aluminum and magnesium elements increases gradually within the range of 1–2 wt.%. The micro-morphology of the coating with different compositions was observed by a scanning electron microscope (SEM). Combined with the surface distribution results of energy dispersive spectrometer (EDS) analysis elements and the phase analysis results of diffraction of X-rays (XRD), the phase distribution of the coating is understood. The statistical calculation of the phase distribution was carried out after staining the SEM image by ImageJ, This is consistent with the solidification simulation results of the thermodynamic simulation software (PADAT). The influence of magnesium and aluminum elements on the microscopic morphology and phase distribution of the zinc–aluminum–magnesium (ZnAlMg) coating was studied, and the mechanism of action was analyzed. The results show that the volume ratio of binary eutectic phase (Zn/MgZn2) and ternary eutectic phase (Zn/Al/MgZn2) in the coating tends to increase as the contents of the two elements elevate. The quantity of MgZn2 is the critical factor for the corrosion resistance of the coating; the more MgZn2, the better the corrosion resistance. [ABSTRACT FROM AUTHOR]

This paper reports on an essential step towards accelerating the development of new, environmentally friendly active protective coatings by structure optimization. The complex microstructure of the pigment particles within a coating have been observed non-destructively in 3D by nano-computed tomography using synchrotron radiation. For the first time, a stochastic geometry model is fitted based on spatial geometric features of the particles observed in the 3D images. The typical cell of a random Gibbs-Laguerre tessellation is used to model the particles' polyhedral shapes as well as the observed joint size and aspect ratio distributions. [Display omitted] • Essential step to simulation and optimization of leaching in active protective coatings • Complex spatial microstructure of pigment particles observed non-destructively in 3D • Stochastic geometry model reproduces variation of sizes, shapes, and their correlation • Model allows to easily alterate the particle distributions starting from the real ones • First step towards a realistic computational model for release of corrosion inhibitors [ABSTRACT FROM AUTHOR]

Surface protective coatings on magnesium alloys have been developed to control the corrosion rate of biomedical magnesium implants under mechano-chemical loadings. Quantifying the effect of coating's microstructural features on the corrosion behaviour of magnesium alloys facilitates the innovative design of biodegradable magnesium implants from the surface to the bulk. The present work is devoted to exploring the applicability of deep learning methods for efficiently predicting the in vitro pitting corrosion behaviour of coated magnesium alloys. To this end, the proposed machining learning method employs different CNN models for predicting the corrosion curve and the evolution of corrosion interfaces. In the proposed deep learning method, phase field simulations with varying coating microstructures are used to generate the required corrosion datasets for training and validating the models. The method is applied to a PEO coated WE43 magnesium alloy to assess its feasibility based on in vitro experiments. Performance analysis shows that the multi-input CNN is superior to the single-input CNN in predicting the corrosion curve. The proposed encoder–decoder architecture can predict the evolution of corrosion interfaces with an average error about 1%. These results demonstrate that the proposed CNN models provide a promising alternative to conventional simulation methods for evaluating the protective performance of coatings. [Display omitted] • Deep learning framework for rapid corrosion prediction of coated magnesium alloys. • The hybrid approach is calibrated with in vitro experiments of a coated magnesium alloy. • The CNN models provide a promising method for evaluating the performance of coatings. • The machine learning approach significantly reduces computational costs. [ABSTRACT FROM AUTHOR]

In 2011, the Great East Japan Earthquake and tsunami caused a hydrogen explosion at the Fukushima Daiichi nuclear power plant, which exposed radioactive materials to the atmosphere and had a very negative impact on the nuclear power industry. Since then, efforts have intensified around the world to make nuclear power safer. Accident-tolerant fuel (ATF) is being developed to prevent the rapid oxidation of zirconium cladding, which directly causes hydrogen explosions. ATF research can be divided into two main approaches: changing the cladding material, or coating the surface of the cladding. Coatings are easier to commercialize and apply to existing nuclear power plants, so most vendors have focused on this approach. Chromium is a popular coating medium because of its superior properties such as a low oxidation rate and excellent adhesion. Therefore, research has been focused on suppressing the rapid oxidation of zirconium cladding in the event of an accident by adding a chromium coating with an appropriate thickness in terms of both economy and effectiveness. Even if the thickness of the coating is fixed, the penetration of oxidizing substances can be further delayed by improving the microstructure of the chromium coating, such as by reducing the grain boundary area. In this study, chromium-coated zirconium cladding tubes were fabricated by the arc ion plating process. The microstructure of the chromium coating was adjusted by varying the negative voltage (0–125 V), which in turn controlled the incident energy at which the chromium ionic particles hit the surface of the cladding tube. Experiments were then performed in 1200 °C steam environment to determine the optimal microstructure for high-temperature oxidation resistance. The development of various material degradation phenomena that occurred during 1200 °C steam oxidation was observed to identify the oxidation mechanism and the main factors of the microstructure that affect the zirconium oxidation rate. [ABSTRACT FROM AUTHOR]

In this work, the composition of the zinc–aluminum–magnesium alloy coating was designed to have a fixed aluminum–magnesium ratio of 1:1, while the content of aluminum and magnesium elements increases gradually within the range of 1–2 wt.%. The micro-morphology of the coating with different compositions was observed by a scanning electron microscope (SEM). Combined with the surface distribution results of energy dispersive spectrometer (EDS) analysis elements and the phase analysis results of diffraction of X-rays (XRD), the phase distribution of the coating is understood. The statistical calculation of the phase distribution was carried out after staining the SEM image by ImageJ, This is consistent with the solidification simulation results of the thermodynamic simulation software (PADAT). The influence of magnesium and aluminum elements on the microscopic morphology and phase distribution of the zinc–aluminum–magnesium (ZnAlMg) coating was studied, and the mechanism of action was analyzed. The results show that the volume ratio of binary eutectic phase (Zn/MgZn2) and ternary eutectic phase (Zn/Al/MgZn2) in the coating tends to increase as the contents of the two elements elevate. The quantity of MgZn2 is the critical factor for the corrosion resistance of the coating; the more MgZn2, the better the corrosion resistance.

In this study, the effect of platinum-aluminide coating parameters on surface roughness of nickel-based superalloy Rene®80 was evaluated. For this purpose, different thicknesses of Pt-layer (2, 4, 6 and 8µm) were plated on the Samples. Then diffusion aluminide coating in two types, high tempeature-low activity and low temperature-high activity was performed. The results of structural investigations by scanning electron microscope and X-Ray diffraction indicated a three-zone structure of coating in all thicknesses of platinum layer, as well as in the two methods of aluminizing. Surface roughness of coatings was measured in three steps: 1-after Pt plating, 2-after Pt diffusion, and 3-after aluminizing and final aging. The results showed that the thickness of Pt and the final thickness of the coating directly affected the surface roughness. The minimum surface roughness was created by high temperature low activity with 2µ of Pt-layer (2.6μm) and the maximum of surface roughness was obtained in low-temperature high activity with 8µ of the Pt-layer (8.8 μm).

Suspension plasma spraying (SPS) as a potential technique to prepare thermal barrier coatings (TBCs) has been attracting more and more attention. However, most reports on SPS were carried out in the atmosphere. Given the unique features of in-flight particles and plasma jets under low pressure, the resulting coatings are expected to be different from those under atmospheric pressure. In this article, yttria-stabilized zirconia (YSZ) thermal barrier coatings were prepared using suspension plasma spraying under different environmental pressures. The results show that as the environmental pressure decreased, the column-like structural coating turned into a vertical crack segmented structure, as well as a dramatic decrease in surface roughness. More nanoparticle agglomerates were formed in the coating under lower environmental pressures. The real porosity of the coating increased with a decrease in environmental pressure. [ABSTRACT FROM AUTHOR]

Drug-coated balloon (DCB) therapy is a promising endovascular treatment for obstructive arterial disease. The goal of DCB therapy is restoration of lumen patency in a stenotic vessel, whereby balloon deployment both mechanically compresses the offending lesion and locally delivers an antiproliferative drug, most commonly paclitaxel (PTX) or derivative compounds, to the arterial wall. Favorable long-term outcomes of DCB therapy thus require predictable and adequate PTX delivery, a process facilitated by coating excipients that promotes rapid drug transfer during the inflation period. While a variety of excipients have been considered in DCB design, there is a lack of understanding about the coating-specific biophysical determinants of essential device function, namely, acute drug transfer. We consider two hydrophilic excipients for PTX delivery, urea (UR) and poly(ethylene glycol) (PEG), and examine how compositional and preparational variables in the balloon surface spray-coating process impact resultant coating microstructure and in turn acute PTX transfer to the arterial wall. Specifically, we use scanning electron image analyses to quantify how coating microstructure is altered by excipient solid content and balloon-to-nozzle spray distance during the coating procedure and correlate obtained microstructural descriptors of coating aggregation to the efficiency of acute PTX transfer in a one-dimensional ex vivo model of DCB deployment. Experimental results suggest that despite the qualitatively different coating surface microstructures and apparent PTX transfer mechanisms exhibited with these excipients, the drug delivery efficiency is generally enhanced by coating aggregation on the balloon surface. We illustrate this microstructure-function relation with a finite element-based computational model of DCB deployment, which along with our experimental findings suggests a general design principle to increase drug delivery efficiency across a broad range of DCB designs.

This study investigates the mechanical properties of aluminium 2024 (Al-2024) and aluminium 7075 (Al-7075) cold-sprayed materials and coatings for repairs. It aims to determine the acceptable data needed to meet regulatory requirement when substantiating cold spray repairs. The study focuses on repairs of non-principal structural element (PSE) structures such as skin and panels that are prone to corrosion and wear. For cold spray repair of such components, the microstructure, tensile, peel, bearing, and bending strength from the repair process and powder materials of Al-2024 and Al-7075, were identified and investigated in accordance with MIL-STD-3021. Results show an average coating porosity of

The formation of a corrosion-resistant coating by the hydrothermal method is an effective way to provide significant protection to magnesium alloys. However, it is a challenge to prepare such a coating on magnesium-lithium alloys because of its high chemical activity. Herein, the dual-layer structured corrosion-resistant conversion coating composed with Mg(OH)2 and LiOH was successfully synthesized on Mg-9Li alloy by the optimization of the hydrothermal reaction in deionized water. The coating synthesized at 140 °C for 2 h has the best anti-corrosion performance in all obtained coatings, which has a uniform and compact coating with thickness of about 3 μm. The improvement of the hydrophobicity due to the stacking structure of the surface layer, as well as the barrier effect of its inner compact coating on corrosive media, lead to the excellent anti-corrosion performance of the obtained hydrothermal conversion coating

In conventional thermal spraying processes, it is difficult to employ one type of coating process to economically spray materials having greatly different melting points. In this study, wire electrical explosion spraying(WEES) was applied to prepare refractory Ta10W and non-refractory Ni60A coatings by using a self-designed WEES device. The coating microstructure, deposition efficiency and coating thickness, as well as the adhesive strength of both coatings were investigated. A uniform and dense Ta10W coating with the phase of Ta, Ta 2 N, and FeTaO 4 can be obtained when the energy density was 151.6 J/mm3, while the uniform and dense Ni60A coating made up of FeNi and SiO 2 phase was got at the energy density of 72.7 J/mm3. The maximum deposition efficiency of Ta10W and Ni60A were 53% and 47% respectively. The thickness increment of both coatings decreased with the explosion frequency. The critical load L c in the scratch test can be regarded as a criterion of the adhesive strength, the average critical load of Ta10W was greater than 50 N, while the Ni60A was 38.3 N. Through developing a high-efficient spray device and choosing the appropriate process parameter, especially a suitable energy density, the WEES will be capable to produce the commercially available coatings with greatly different melting points. • A set of high-performance wire electrical explosion spray (WEES) device was developed. • The refractory Ta10W and the non-refractory Ni60A was sprayed by the WEES technology. • The deposition efficiency and coating thickness of both coatings were investigated under continuous multiple sprays. • The adhesive strength of both coatings were characterized by the scratch test. [ABSTRACT FROM AUTHOR]

In this study, the effect of platinum-aluminide coating parameters on surface roughness of nickel-based superalloy Rene®80 was evaluated. For this purpose, different thicknesses of Pt-layer (2, 4, 6 and 8µm) were plated on the Samples. Then diffusion aluminide coating in two types, high tempeature-low activity and low temperature-high activity was performed. The results of structural investigations by scanning electron microscope and X-Ray diffraction indicated a three-zone structure of coating in all thicknesses of platinum layer, as well as in the two methods of aluminizing. Surface roughness of coatings was measured in three steps: 1-after Pt plating, 2-after Pt diffusion, and 3-after aluminizing and final aging. The results showed that the thickness of Pt and the final thickness of the coating directly affected the surface roughness. The minimum surface roughness was created by high temperature low activity with 2µ of Pt-layer (2.6µm) and the maximum of surface roughness was obtained in low-temperature high activity with 8µ of the Pt-layer (8.8 µm). [ABSTRACT FROM AUTHOR]

Uniformity, surface roughness, and chemical phase structure are all important features of implant coatings. While the first two variables are important for implant placement, the phase structure affects implant fixation. This study examined the coating morphology and the amount, size, and distribution of crystalline regions of press-fit and screw-type dental implants. Implants obtained from five commercial vendors were sectioned sagitally, mounted, and polished to reveal the coating microstructure. The crystalline phase content varied depending on the implant supplier; however, general trends were observed. Amorphous regions were predominantly found at the metal interface and decreased toward the outside of the coating, producing a crystallinity graded coating. The distal end of the implant, where heat build-up was more likely during the coating procedure, displayed a higher crystalline content and larger crystalline regions. Similarly, the thread apex consisted of more of a crystalline phase. The results of this study of coating microstructure may be used to improve the quality and performance of implants and may help to explain different in vivo responses to the many available varieties of hydroxyapatite-coated dental implants. [ABSTRACT FROM AUTHOR]

Abstract This study presents the elaboration of controlled microstructure of yttria stabilized zirconia (8YSZ) coatings by using an axial suspension plasma spraying (SPS) system. Several 8YSZ coatings were fabricated from porous to dense by using same starting feedstock powder via adjustment of the suspension concentration and the deposition distance. The microstructure control is strongly related to the flying droplet size and its momentum in front of the substrate surface. Both aspects significantly determine the droplet flattening behavior, the deposit size, and therefore the final coating microstructure. Graphical abstract Unlabelled Image Highlights • Axial suspension plasma spraying and controlling the coating microstructure • Suspension solid-load content, spraying distance and droplet size • Droplet trajectory, momentum, and impacting on substrate • 8YSZ coatings from porous to dense microstructure by same system [ABSTRACT FROM AUTHOR]

The microstructure of coating layers has important effects on final properties of paper. Eco-friendly bio-latex derived from sustainable starch has being increasingly used in paper coatings to substitute part of the petroleum-based synthetic latex as pigment binder. The influence of starch-based bio-latex on microstructure and surface properties of coatings such as surface composition, surface morphology, void fraction and water absorbency was studied in this paper. X-ray photoelectron spectroscopy (XPS) results showed that bio-latex addition led to a nearly linear decrease in surface carbon content for coatings dried at high temperature. Scanning electron microscope (SEM) images demonstrated that bio-latex addition may cause a lack of binder film at the coating surface that binds pigment particles, which was in agreement with the XPS results. The coatings demonstrated a marginal increase in surface roughness and some decrease in gloss with the addition of bio-latex, as was expected when starch-based binder was used. Unexpectedly, the void fraction of coatings increased slightly, which was contrary to the case in conventional cooked starch. The coatings had a significant decline in water contact angle after bio-latex addition, indicating a considerable increase in water absorbency. The changes in coating microstructure may be attributed to the unique core-shell structure and water-swollen nature of starch-based bio-latex particles. [ABSTRACT FROM AUTHOR]

Cold spray is a technique allowing the deposition of metallic powders on several different substrates. The deposition process is ruled by different factors, among these, of particular interest are the superficial roughness and texturing of the substrate. The aim of this research was to study the influence of different superficial texturing on the deposition process of aluminium powders on an AA 2024 T3 plate. Samples with different superficial texturing were produced by laser engraving through a Yb:YAG fibre laser, varying the laser treatment parameters. Aiming to highlight the influence of the laser treatment, the deposition process was carried out on all the samples under the same spraying condition. The cross-section of the interface between the substrate and the coating and the microstructure of the coating itself were observed to study the influence of the superficial texturing on the coating formation. It was found that the superficial texturing influences both the adhesion mechanism and the microstructure of the coating. [ABSTRACT FROM PUBLISHER]

In this study, the AlTiCrN coatings with different Cr contents were deposited from AlTi and Cr targets using a hybrid coating process that combines high power impulse magnetron sputtering with DC magnetron sputtering. The microstructure and mechanical properties of the AlTiCrN coatings were investigated using X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy, and nano-indentation. The tribological behaviors of the AlTiCrN coatings were evaluated by pin-on-disk tribo-tests at 400 °C, 600 °C and 800 °C, respectively. The results indicated that all the AlTiCrN coatings exhibited (Al,Ti,Cr)N solid solution phases with FCC NaCl-type structure. With increase in Cr target power, the Cr content increased from 0 to 25 at. %, tailoring changes in coating microstructure and properties. Firstly, the preferred orientation shifted from (111) to (200). Secondly, the hardness and elastic modulus of the AlTiCrN coatings increased from 31.4 ± 1.4 GPa and 448.8 ± 9.3 GPa at 0 at.% Cr to 33.7 ± 1.4 GPa and 469.5 ± 8.2 GPa at 8.9 at.% Cr, and then decreased with further increase in Cr content. Thirdly, the friction coefficient and wear rates of the coatings against Al 2 O 3 balls also exhibited some relationship with the coating compositions and test temperatures. The inherent mechanism was analyzed and discussed. [ABSTRACT FROM AUTHOR]

Heavy steel automotive parts have been replaced with aluminum-based lightweight materials worldwide. In particular, grey cast iron engine blocks, which are very heavy components in vehicles, have been replaced by aluminum-silicon hypoeutectic alloys in order to reduce emissions and fuel consumption. However, aluminum alloys are not able to withstand severe engine cylinder conditions due to their poor mechanical properties. In this study, a Mo blended ferrous coating was fabricated using atmospheric plasma spraying to replace the grey cast iron liner in the automotive cylinder bore. Five fractions of Mo, 0, 5, 10, 15, and 20 wt%, with ferrous powder were prepared to investigate the effect of Mo on the microstructure and mechanical properties of coatings. All of the Mo-added coating layers showed significantly improved mechanical properties, such as hardness and wear resistance compared to that of grey cast iron. However, as Mo content exceeded 10 wt% of the blend, the tribological properties gradually degraded due to brittle fracture of Mo. As a result, 10 wt% Mo blended with ferrous powder provided optimized mechanical properties and can be substitute for grey cast iron liners in the automotive industry. [ABSTRACT FROM AUTHOR]

The paper presents coatings obtained using two different stainless steel (AISI 316) and marine bronze (CuAl8) wires sprayed with electric arc spraying. Substrate: mild steel S235J2 (LST EN 10025: 2004). Arc spray equipment - “EuTronic Arc Spray 4” with an additional power source. The main task was to select optimal technological spraying process and obtain coatings which possess the best mechanical, physical, tribological properties that meet the requirements of the specific requirements in service coatings. The microhardness, elastic modulus, and morphology was examined. Dry friction wear was assessed in the mass loss of the coatings. The results of tribological coatings properties were assessed in determining the mass lost. [ABSTRACT FROM AUTHOR]

This paper studies the microstructure, sliding wear behavior and corrosion resistance of high-velocity oxygen fuel (HVOF)-sprayed FeVCrC-based coatings. Various process parameters were tested to evaluate their effects on the coating properties, which were also compared to those of HVOF-sprayed NiCrBSi and Stellite-6 coatings. The Fe alloy coatings are composed of flattened splats, originating from molten droplets and consisting of a super-saturated solid solution, together with rounded particles, coming from partially unmolten material and containing V- and Fe-based carbide precipitates. All process parameters, apart from 'extreme' settings with excess comburent in the flame, produce dense coatings, indicating that the feedstock powder is quite easily processable by HVOF. These coatings, with a microhardness of 650-750 HV, exhibit wear rates of ≈2 × 10 mm/(Nm) in ball-on-disk tests against sintered AlO spheres. They perform far better than the reference coatings, and better than other Fe- and Ni-based alloy coatings tested in previous research. On the other hand, the corrosion resistance of the coating material (tested by electrochemical polarization in 0.1 M HCl solution) is quite low. Even in the absence of interconnected porosity, this results in extensive, selective damage to the Fe-based matrix. This coating material is therefore unadvisable for severely corrosive environments. [ABSTRACT FROM AUTHOR]

The study focuses on the role of silicon in the hot dip galvanizing process. Coating formation and growth were analysed. Centrifugal casting was used to prepare steel substrates with different silicon concentrations (< 0.01%, 0.06%, 0.11%, 0.17%, and 0.30%). Hot dip galvanizing was performed at 450 °C in the industrial galvanizing plant Zincpot (Estonia). The galvanizing time for coating formation was 4-25 s and for coating growth 195 and 1200 s after a longer incubation time. The thickness of the coating was measured and the microstructure of the Zn-Fe coating was examined. Even a very short time contact (4 s) between steel and zinc led to the formation of Fe-Zn intermetallics. The first phase was the ζ phase, immediately followed by the δ and then, after incubation the Γ phase. The reactions that took place in the galvanizing process during the shorter dipping times (< 25 s) were not influenced by silicon concentrations, but the influence of silicon was remarkable after longer dipping times (> 25 s). A schematic model of zinc coating formation is presented. Silicon affects hot dip galvanizing reactions by influencing Zn diffusion into steel and Fe diffusion into the coating. [ABSTRACT FROM AUTHOR]

Ni–40% WC composite coatings were prepared on 40Cr surfaces by high frequency induction cladding and then were treated by electrical contact strengthening (ECS) to further improve the coating properties. The effects of ECS on the coating microstructure, microhardness, phase transformation and wear behaviour were investigated using optical microscopy, field emission scanning electron microscopy, Vickers hardness measurements, X-ray diffraction and rolling contact wear tests. As the contact current increased, the porosity and grain size of the resulting composite coating decreased, and its cohesion increased. The hard phase in the coatings also diffused further. After ECS treatment, the average hardness of the Ni–40% WC composite coatings ranged from 652 HV 0.1 up to 906 HV 0.1 . As demonstrated by the results of the rolling contact wear tests, the composite coatings treated by ECS exhibited improved wear resistance. [ABSTRACT FROM AUTHOR]

Metallic coatings were processed on a 35CrMo4 substrate using a thermal flame spray technique. The deposited metal was a high carbon steel, low alloyed with Cr, Mn and Si. In those coatings FeO and Fe 3 O 4 oxides were found, as well as stable α-ferrite phase and some γ-austenite phase. γ-Austenite phase is metastable and transforms into stable α-ferrite during annealing treatment at 300 °C. This γ to α-phase transformation, as well as the evolution of the oxides during the annealing post-treatment, has some influence on the mechanical properties of the coating: hardness, tribological properties, Young's modulus and adhesion on the 35CrMo4 substrate. [ABSTRACT FROM AUTHOR]

The paper presents the results of investigation of pulse atomizing air jet application in electric arc metallizing. To ensure the pulsed mode, the respective device was developed allowing control of outflowing of a jet with frequency within 0-130 Hz. Oscillograms of variation of dynamic pressure are given. Dependence of pulse atomizing air jet on frequency of closing the spray gun nozzle channel is shown. Coating microstructures are given. Influence of pulsation frequency on composition of coatings spray-deposited with PP-MM-2 wire is shown. 15 Ref., 6 Figures. [ABSTRACT FROM AUTHOR]

Abstract: Yttria-stabilized zirconia (3YSZ) coatings were successfully obtained by suspension plasma spraying. The coatings present generally two-zones-microstructure comprising nanostructured zones contributed by unmolten, partially sintered nanoparticles surrounded by lamellar splats formed from molten and agglomerated in-flight fine solids. In addition, different types of cracks inside the coating microstructure were classified and quantified by image analysis such as e.g. inner microcracks and segmentation cracks associated with quenching process as well as horizontal interlamellar cracks. Thermophysical properties of sprayed coatings were tested with a thermal diffusivity set up basing onto light flash principle. Subsequently, the thermal conductivity was determined with the use of literature data of density and specific heat. The calculations showed very low thermal conductivities values. The values did not correlate with coatings porosity data. Consequently, the analysis of variance (ANOVA) test allowed evaluating the possible impact of the various types of cracks on thermal conductivity. By this analysis, a good correlation between vertical cracks, which include microcracks and segmentation cracks, and thermal conductivity was found. The findings also confirmed the increase of thermal conductivity associated with this type of cracks. [Copyright &y& Elsevier]

In recent years, cobalt has been known as an alternative coating material to chromium in corrosion and erosion resistant applications. Extensive research has been carried out on a variety of electroplated cobalt coatings. In this study, for the first time, the relative priority of cobalt coatings has been evaluated by using the Analytic Hierarchy Process (AHP), in combination with empirical methods. In the first step, Cu substrates have been coated with Co under different experimental conditions. The SEM micrographs of Co coatings have been analyzed via image analysis (Clemex) software. In the second step, through the AHP and the Expert Choice software, benefiting from expert opinions, the relative weights of the effective parameters with an influence on microstructure have been calculated. Subsequently, by using the weights obtained, the relative priority of alternatives was calculated and the quality of coatings was ranked. The predicted ranking has been found to be in consistence with the experimental results. This result shows that before experimental tests, the best alternatives to achieve the ultimate goal could be anticipated. This anticipation leads to reduce in trial and error and the multiplicity of the tests in investigations. [ABSTRACT FROM AUTHOR]

Abstract: The microplasma synthesis of the surface layers on aluminum alloy 2024 was studied by optical emission spectroscopy in situ. The evolutions of atomic line intensities in emission spectra and the properties of obtained coatings are discussed. The evolution in the chemical composition of plasma microdischarges and coatings layer structure in the light of previously obtained data on the dynamics of phase transformation by EPR and semi-quantitative X-ray analysis were compared. In the early stages of the synthesis of the plasma consists mainly of the substrate components, but with coating thickness increasing the electrolyte components become dominant. The formation of a dense layer enriched with α-Al2O3 requires specific conditions, which can be found from the changes in the emission spectra of microdischarges radiation. [Copyright &y& Elsevier]