Coating Deposition Process Research Articles

Deposition of fully dense Al-based coatings via in-situ micro-forging assisted cold spray for excellent corrosion protection of AZ31B magnesium alloy

In this work, three types of fully dense aluminum-based (Al) coatings (pure Al, AA2219 and AA6061) were deposited on AZ31B magnesium (Mg) alloy by a recently developed in-situ micro-forging assisted cold spray process. The detailed microstructure, coating adhesion and corrosion protection performance were systematically investigated. Results show that the porosities of the pure Al, AA2219 and AA6061 coatings are as low as 0.34 ± 0.11%, 0.23 ± 0.09% and 0.24 ± 0.08%, respectively. Strong adhesion strength (83.6–91.5 MPa) was achieved for the Al-based coatings due to the in-situ micro-forging induced enhanced mechanical-interlocking between Al-based coating and the magnesium alloy substrate. The corrosion current density of the AZ31B Mg alloy decreases to 1.9–5.8 μA cm−2 from 312.8 μA cm−2 after coated with the Al-based coatings. The long-term corrosion tests further indicate that the Al-based coatings are not aqueous solution permeable during the entire 1000 h immersion, thus provided robust long-term corrosion protection of AZ31B Mg alloy substrate. Moreover, the difference in corrosion resistances among the three Al-based coatings was observed and was further explained based on their unique microstructures arising from the coating deposition process. The present in-situ micro-forging assisted cold spray process shows great potential for economical and effective corrosion protection of magnesium alloy and provides more freedom for industries to design and use magnesium alloy parts.

A residual stresses numerical simulation and the relevant thermal-mechanical mapping relationship of Fe-based coatings

Abstract Residual stresses model comprehensively considers the three main sources of residual stress during the coating deposition process: quenching stress, thermal stress and phase transformation-induced stress. With the deposited layer temperature, coating thickness, number of deposited layers and relevant workpiece dimensions as the input, the model can easily calculate the final residual stress distribution in the coating. Moreover, the thermal–mechanical behavior during the coating deposition process was revealed through experimental and theoretical analysis of coatings. The results showed that the coating fabricated within the range of 65.2–122.5 °C have relatively low residual stresses, ensuring relatively high service reliability.

Highly conductive ultra-sensitive SWCNT-coated glass fiber reinforcements for laminate composites structural health monitoring

In the present study, hierarchical single-wall carbon nanotube covered Glass fibres (GF-CNT) are developed for self-sensing Structural Health Monitoring (SHM) of epoxy laminate composites. The unidirectional (UD) CNT-modified glass fibers were fabricated by a versatile and scalable wet-chemical blade coating deposition process under ambient conditions. GF-CNT were employed to manufacture UD damage sensing composite laminates. Scanning Electron microscopy (SEM) revealed an extremely homogeneous CNT nanolayer consisting of highly entangled CNT networks covering fully the GF surfaces. A comprehensive electrical characterization of the manufactured laminate was carried out, revealing a strongly orthotropic response in terms of electrical resistivity. The damage sensing capability of the new developed “smart” reinforcement material was verified taking advantage of mode I Double Cantilever Beam (DCB) tests carried out on specimens with a pre-delamination. The electrical resistance, measured during the tests, exhibited a pronounced increase proportional to the delamination growth. The experimental data were also compared with the assessment of a predictive analytical model, showing a very satisfactory agreement.

Development of deposition process of cerium-containing protective coatings on alloyed steel

Development of deposition process of cerium-containing protective coatings on alloyed steel

КОНЦЕПЦИЯ САЕ-СИСТЕМЫ ПРОЕКТИРОВАНИЯ ПРОЦЕССА НАНЕСЕНИЯ ЗАЩИТНЫХ ПОКРЫТИЙ ДЛЯ УПРОЧНЕНИЯ И ВОССТАНОВЛЕНИЯ ДЕТАЛЕЙ ТЕХНОЛОГИЧЕСКОГО ОБОРУДОВАНИЯ

КОНЦЕПЦИЯ САЕ-СИСТЕМЫ ПРОЕКТИРОВАНИЯ ПРОЦЕССА НАНЕСЕНИЯ ЗАЩИТНЫХ ПОКРЫТИЙ ДЛЯ УПРОЧНЕНИЯ И ВОССТАНОВЛЕНИЯ ДЕТАЛЕЙ ТЕХНОЛОГИЧЕСКОГО ОБОРУДОВАНИЯ

Mathematical model of deposition process of composite coatings based on intermetallic Ti-Al system by vacuum arc

This work is devoted to mathematical modeling of the process of deposition of composite coatings based on intermetallics of the Ti-Al system from vacuum-arc plasma, considering diffusion processes between alternating layers in order to predict the phase composition of the coating. The physical and chemical processes occurring during layer-by-layer deposition of multilayers coatings based on intermetallics of Ti-Al system by vacuum arc plasma in thin films were investigated. The processes occurring in the deposition of coatings based on intermetallic Ti-Al system by vacuum arc plasma were mathematically described. Diffusion processes were simulated using the finite element method. Diffusion processes occurring between layers of Ti and Al were modeled using Fick equations. Software based on mathematical model that allows to calculate the optimal deposition modes of coatings based on intermetallic Ti-Al system was developed. Influence of the deposition conditions on the content of intermetallic compounds in the coating was determined by X-ray diffraction methods. Results of mathematical model of deposition multilayer coatings considering diffusion processes were compared with experimental data. It is established that in the layer-by-layer deposition of titanium and aluminum, there are two mechanisms for the formation of intermetallic phases: due to diffusion processes and chemical reactions of samples running on the surface. A correlation between the percentage content of intermetallic phases in the coating and the diffusion processes between titanium and aluminum was established.

Chemical deposition process for coatings: the problems of mass and heat transfer

The known variants of deposition of thermal barrier coatings (TPC) of ZrO2-Y2O3 by the MO CVD method are analyzed. It is established that the use of this method in principle allows obtaining ceramic coatings with the required columnar structure, low thermal conductivity and technologically acceptable growth rates. It is shown that the main limiting factor in the coating growth rate is the productivity of the precursor vapor sources used. The analysis of known variants of realization of heat and mass transfer at the use of various precursors with a wide range of thermal parameters for the given process is carried out. The results of experimental studies and numerical modeling of the kinetics of sublimation of a number of precursors in the flow of an inert gas Ar, He or their mixtures in a given range of temperatures and gas flow rates are obtained. It is established that when sublimating a single precursor particle under forced convection, the mass transfer intensity of a given compound in the helium stream is several times greater than mass exchange in argon with other closely related parameters, such as the flow velocity and the temperature of the oncoming flow. At the same time, the temperature of the particle is lowered, which can be an important factor in increasing the thermal stability of the vapors. It is shown that there is an additional possibility to control the sublimation of the precursor with the Ar/He mixture.

Investigation of a nickel coating deposition processes from solid nickel electrolyte

Nickel is the basis of most of the heat-resistant materials used in the aerospace industry for power plant parts. Recently, the method of electrolytic coating with nickel is used to create protective coatings on aluminum, magnesium, zinc and cast irons. It is known to use the method of nickel plating of aluminum and magnesium alloys, in particular to protect the duralumin blades of screw aircraft. The lifetime of nickel-plated cast-iron drums for drying in paper production is significantly higher than in conventional cast iron, and paper quality is also improving. The aim of the work is to influence the concentration of hypophosphite on the kinetics of the cathode process and on the properties of the resulting nickel coating.

Structure Formation Features of Corrosion-Resistant Powder Material Type 316L Gas-Flame Sprayed Coating

Implementation of the extensive possibilities of the gas-flame spraying technique with respect to the main advantages of the powder metallurgy is only possible with a methodologically justified approach to materials selection, a study of gas-dynamic processes taking place in equipment during coating formation (powder flow rate, temperature and fl ame type, etc.), and control of metallurgical processes (structure formation, liquation, phase transitions, etc.). Such phenomena need to be controlled both at the stage of initial wire and powder production, and during coating deposition. In practice, the choice of coating materials for the oil and gas industry (such as pipes, distillation columns, pumping units), should not solely be based on powder chemical composition. Features of coating structure are typically not taken into account, which are interrelated both with the initial powder or wire formation technique, and with coating deposition process parameters. This work demonstrates the differences in structure formation within steels and gasflame coatings of the similar alloy composition. A direct relationship of structure formation in gas-flame coatings is established not only with deposition technology, but mostly the method of forming the initial powder material structure. It is shown that for the effective application of coating material it is necessary to determine the alloy system, the structural class and formation technology of the powder material connected with possible inheritance and/or structure-phase transformations during coating deposition.

Regeneration of manganese electrolyte during continuous electrolysis of manganese coatings

Water pollution in the electrolytic manganese metal (EMM) industrial production process is a serious problem, and the manganese and ammonia nitrogen concentration in the rivers near EMM plants still exceeds the standards. An environment-friendly regeneration method of the manganese electrolyte (ME) that reduces the duration of the electrodeposition process and saves water resources for ME preparation in laboratories was proposed. Thus, electrolytic manganese metal powder (EMMP) was dissolved in ME and the addition of hydroxylamine sulphate altered significantly the dissolution effect of EMMP in ME. The provided ME regeneration scheme allows to extend duration of the Mn coating deposition process up to one week without changing ME, just only adding the electrolyte prepared by dissolving EMMP in an anolyte. EMMP losses did not exceed 5–7% from the mass of the electrodeposited Mn coatings on the cathode. Ammonium selenate was dissolved in ME by periodically dissolving 2% of the salt from the mass of the electrodeposited Mn coating on the cathode at an electrolyte temperature of 30–40°C.

The Influence of the Coating Deposition Process on the Interdiffusion Behavior Between Nickel-Based Superalloys and MCrAlY Bond Coats

In this work, interdiffusion between two nickel-based superalloys and two MCrAlY bond coats is investigated. The MCrAlY bond coats were applied using two different spraying processes, high velocity oxygen fuel spraying (HVOF) and low-pressure plasma spraying. Of primary interest is the evolution of Kirkendall porosity, which can form at the interface between substrate and bond coat and depends largely on the chemical compositions of the coating and substrate. Experimental evidence further suggested that the formation of Kirkendall porosity depends on the coating deposition process. Formation of porosity at the interface causes a degradation of the bonding strength between substrate and coating. After coating deposition, the samples were annealed at 1050 °C for up to 2000 h. Microstructural and compositional analyses were performed to determine and evaluate the Kirkendall porosity. The results reveal a strong influence of both the coating deposition process and the chemical compositions. The amount of Kirkendall porosity formed, as well as the location of appearance, is largely influenced by the coating deposition process. In general, samples with bond coats applied by means of HVOF show accelerated element diffusion. It is hypothesized that recrystallization of the substrate material is a main root cause for these observations.

Hybrid Aerosol Deposition Process for Ceramic Coatings

Hybrid Aerosol Deposition Process for Ceramic Coatings

One-step immersion plating method to deposit anticorrosion nickel-sulfur coatings on copper

Although nickel has a lower standard electrode potential than copper, nickel-sulfur coatings were successfully deposited on copper through one-step immersion plating method, which was carried out in the aqueous solution consisting of NiSO4·6H2O and Na2S2O3·5H2O at room temperature. The open circuit potential tests demonstrated that copper had a more negative potential than nickel in Na2S2O3·5H2O solutions, which made the deposition of nickel on copper through immersion plating feasible. Because of the decomposition of sodium thiosulfate, sulfur could be codeposited with nickel and the nickel-sulfur coatings were finally obtained. The surface morphology and composition of the coatings were characterized with SEM, EDS, XPS and XRD analyses, and the results indicated the coatings were mainly composed of metallic nickel and Ni3S2. The deposition process of the nickel-sulfur coatings was investigated by analyzing the morphology evolution of copper substrates. The as-prepared nickel-sulfur coatings possessed good anticorrosion ability for its compact structure and could lower the corrosion current density of copper in 3.5wt% NaCl solution to its 1/20.

Electrostatic Solid Lubricant Coatings: Optimization of Process Parameters and Performance in Tribological Tests

The scope of this study is to optimize the electrostatic solid lubricant coating deposition process parameters such as electric potential, solid lubricant feed pressure and distance between the nozzle tip to metal substrate on its average surface roughness of the coatings. Statistical design approach was used to plan and confirm the experimental investigation. In addition, tribological performance of coatings is assessed through pin-on-disc tests under dry sliding conditions. Results demonstrate that the electric potential has the most significant effect on the roughness of coatings. Electrostatic solid lubricant coatings works quite satisfactorily in dry sliding conditions and can endow in making sliding process more environmental friendly.

Hybrid biocomposites based on titania nanotubes and a hydroxyapatite coating deposited by RF-magnetron sputtering: Surface topography, structure, and mechanical properties

In this study, biocomposites based on porous titanium oxide structures and a calcium phosphate (CaP) or hydroxyapatite (HA) coating are described and prepared. Nanotubes (NTs) with different pore dimensions were processed using anodic oxidation of Ti substrates in a NH4F-containing electrolyte solution at anodization voltages of 30 and 60V with a DC power supply. The external diameters of the nanotubes prepared at 30V and 60V were 53±10 and 98±16nm, respectively. RF-magnetron sputtering of the HA target in a single deposition run was performed to prepare a coating on the surface of TiO2 NTs prepared at 30 and 60V. The thickness of the CaP coating deposited on the mirror-polished Si substrate in the same deposition run with TiO2 NTs was determined by optical ellipsometry (SE) 95±5nm. Uncoated and CaP-coated NTs were annealed at 500°C in air. Afterwards, the presence of TiO2 (anatase) was observed. The scanning electron microscopy (SEM), X-ray diffraction (XRD), photoelectron spectroscopy (XPS) and nanoindentation results revealed the influence that the NT dimensions had on the CaP coating deposition process. The tubular surfaces of the NTs were completely coated with the HA coating when prepared at 30V, and no homogeneous CaP coating was observed when prepared at 60V. The XRD patterns show peaks assigned to crystalline HA only for the coated TiO2 NTs prepared at 30V. High-resolution XPS spectra show binding energies (BE) of Ca 2p, P 2p and O 1s core-levels corresponding to HA and amorphous calcium phosphate on TiO2 NTs prepared at 30V and 60V, respectively. Fabrication of TiO2 NTs results in a significant decrease to the elastic modulus and nanohardness compared to the Ti substrate. The porous structure of the NTs causes an increase in the elastic strain to failure of the coating (H/E) and the parameter used to describe the resistance of the material to plastic deformation (H3/E2) at the nanoscale level compared to the Ti substrate. Furthermore, only the HA coating on the NTs exhibits a significantly increased H/E ratio and H3/E2 factor compared to the NTs and Ti substrate. Increases in resistance to penetration for the indenter were also observed for HA-coated TiO2 NTs prepared at 30V compared to uncoated and CaP-coated NTs prepared at 60V.

Modelling emission spectra of the gas-discharge plasma for the aims of its analysis and parameters estimation

In this paper modelling of the emission spectra of gas-discharge plasma using the data about the electronic transitions in substances under the assumption of local thermodynamic equilibrium is discussed. The possibility of using these spectra to simplify the analysis of the plasma composition during the coating deposition process and determine the parameters of the gas-discharge plasma are shown.

Heat flux investigations during flame thermal spray process using the lumped capacitance method

The evaluation of heat flux is vital in the field of thermal spray process since it decides the temperature gradient, the formation of the residual stress inside the coating and finally affects the coating properties. Especially for the specific net incident heat flux density launched by the torch during each passage, it affects greatly the interaction between the previous and latter adjacent layers, the temperature gradient formation as well as the residual stress distribution along the vertical direction during the coating deposition process. This work mainly concentrates on the estimation of heat flux density during flame thermal spray process based on a lumped capacitance model. The heat flux evolution during one multi-pass of the torch was analyzed in detail and the average heat flux density impinging the substrate surface was firstly estimated, the root mean square error between the measured temperature and the numerical estimation was selected as the evaluation criteria to compare the calculation accuracy. The dynamic increase of coating mass was then added into consideration and the net incident heat flux density launched by the torch was estimated. The peak power value of the heat flux density was estimated based on an assumed Gaussian form of thermal energy distribution.

Comparison of experiments and computations for cold gas spraying through a mask. Part 2

This paper presents experimental and simulation results of cold spray coating deposition using the mask placed above the plane substrate at different distances. Velocities of aluminum (mean size ~ 30 μm) and copper (mean size ~ 60 μm) particles in the vicinity of the mask are determined. It was found that particle velocities have angular distribution in flow with a representative standard deviation of 1.5–2 degrees. Modeling of coating formation behind the mask with account for this distribution was developed. The results of model agree with experimental data confirming the importance of particle angular distribution for coating deposition process in the masked area.

Surface Engineering Analysis of D-Gun Sprayed Cermet Coating in Aggressive Environment

Material degradation due to hot corrosion is a common problem in many engineering system, including coal fired turbines, valves and boiler tubes leading to huge economy losses. Detonation Gun process is a novel coating deposition process among the other thermal spray processes due to its very low porosity, strong adhesion to substrates, high cohesive strength and high hardness. In the present investigation, D-Gun process has been used to deposit Cr3C2–25NiCr coating on 23/8N Nitronic steel. The oxidation behavior of D-Gun sprayed Cr3C2–25NiCr coatings subjected to high temperature (700°C) in actual coal fired boiler for 1000 hours has been carried out in the present work. X-ray diffraction, Field emission–scanning electron microscope technique was used to analyze the scales formed on the surface of the oxidized samples. High volume fraction of carbides contributed for the higher microhardness of the coating (970HV). No microspalling of the scales were showed by the coated specimen. The scale remained intact and adherent to the substrate. The development of protective oxide scale of chromium, nickel and spinel of nickel and chromium have contributed the better oxidation resistance for coated specimen. The Cr3C2-25 NiCr coating imparted better hot corrosion resistance than the uncoated one in the given environment.

The influence of precursor gas pressure on structure and properties of fluoropolymer coatings by hot wire CVD

In this paper we investigated the deposition process of the fluoropolymer coatings by the method of Hot Wire Chemical Vapor Deposition. The dependence of precursor gas pressure on deposition rate, structure and properties of the formed film was investigated. The study has shown that the increasing of precursor gas pressure leads to change of the film structure from porous to continuous with globules and further to solid that have different wettability. Depending on the mode of deposition was obtained the fluoropolymer coating with different structure: the wetting angle changed from 60 to 170°. A mechanism of the formation of fluoropolymer coating was discussed.