Multilayer Protective Coatings Research Articles

Химический состав, структура и микротвердость многослойных высокотемпературных покрытий

Introduction. Plasma spraying is one of the modern and effective methods for coatings application for various purposes and compositions. With the help of thermal plasma flows, it is possible to spray almost any powder materials (ceramic, metal, metal-ceramic). Plasma spraying of multilayer protective coatings can be successfully used to increase the durability of pierced mandrels, which are the main tool in the production of hollow billets. The purpose of this work is to study the chemical composition, structure, and microhardness of multilayer high-temperature coatings of two different compositions deposited by plasma spraying, which are supposed to be used to increase the durability of pierced mandrels. Materials and research methods. The deposition of multilayer coatings of two compositions was carried out on a plasma-powder spraying unit with contact excitation of an arc discharge UPN-60KM TSP2017. Coatings were obtained by sequential deposition of three layers with different powder compositions. After deposition of all three coating layers, oxidative annealing was carried out at a temperature of 900°C to form a dense scale layer of FeO + Fe2O3 + Fe3O4 on the surface. The chemical composition of the coatings was studied by X-ray microanalysis using a TESCAN scanning electron microscope with an OXFORD attachment. The microstructure of the coatings was studied using a NEOPHOT metallographic microscope. Phase X-ray diffraction analysis was performed on a SHIMADZU diffractometer in Kα chromium radiation. Microhardness was measured on a LEICA hardness tester at a load of 50 g. Results and discussion. The nature of the distribution of chemical elements over the thickness of the coating, consisting of four layers, is established: an inner metal layer that provides protection against high-temperature corrosion; a transitional metal layer designed to equalize the thermal properties between the layers; α-Fe metal oxide layer and iron oxides and external thermal barrier oxide layer FeO + Fe2O3 + Fe3O4. Coatings are characterized by a non-uniform distribution of structural components and microhardness over its thickness. The microhardness of the inner layer reaches 1,400 HV0.05, the transition layer is 800 HV0.05, and the metal oxide layer is 300 HV0.05.

Composition, Structure, and Properties of Ti, Al, Cr, N, C Multilayer Coatings on AISI W1-7 Alloyed Tool Steel

New methods of diffusion metallization of AISI W1-7 steel have been developed. The paper proposes a comparative analysis of the properties and characteristics of AISI W1-7 steel after three methods of chemical heat treatment: diffusion nitriding, nitrogen titration by physical deposition from the gas phase, and diffusion chromium plating with subsequent titanium alloys. The results are presented as a comprehensive analysis of coatings: metallographic, micro-X-ray spectral, X-ray phase, durometric, heat resistance, and wear resistance. It is established that multilayer protective coatings are formed as a result of treatments. It is shown that the coatings consist of carbide and nitride zones, intermetallic, and an Al2O3 layer outside the coating. The coatings have been found to contain barrier layers that prevent aluminum from penetrating the substrate. The maximum microhardness is typical for layers based on titanium carbide—30.3–35.5 GPa and titanium nitride—22.0–22.6 GPa, heat-resistant steels AISI W1-7 at a temperature of 900 °C in 4.2–8.5 times and wear resistance under sliding friction without lubrication up to 5.4 times compared to samples without treatment.

МОЖЛИВОСТІ БАГАТОШАРОВИХ ЗАХИСНИХ ПОКРИТТІВ

The article discusses the problem of using multilayer protective coatings for weapons and military equipment in order to provide protection from atmospheric and aggressive environments and mask objects simultaneously. The difference between these coatings from the known paint coatings is that they are capable of performing several functions simultaneously. The practical use of multilayer protective coatings allows you to increase the combat effectiveness of weapons of the Land Forces. Multilayer protective coatings are the most affordable and effective means of protecting weapons and military equipment products formed on the surface of products as a result of the application of liquid paints and their drying. The urgency of work in this area is due to the fact that at present there are no means of enhancing the protection of the application of liquid paints due to the use of protective coatings. Thus, the urgency of solving the problems associated with improving the protection of the application of liquid paints by the use of multi-layer protective coatings is unconditional at this time. Camouflage coloring reduces the visibility of military equipment and weapons due to the merging of individual color spots with the surrounding background and reduces the range of detection and identification of equipment and weapons when reconnoitered by photographing and observing with the naked eye or in electron-optical and optical devices. In addition, camouflage coloring increases the effectiveness of masking equipment with service tools and local materials at hand. The article shows that due to the preventive application of multilayer protective coatings, it is possible to successfully increase protection and camouflage and, consequently, the combat effectiveness of weapons and military equipment. The purpose of this article is to address the issue of the protection of the application of liquid paints through the use of multi-layer protective coatings. Keywords: protective coatings, paint, weapons and military equipment, multilayer protective coatings, liquid paints, camouflage coloring, combat effectiveness of weapons and military equipment.

Application of electric spark doping technology for strengthening the surface of the Part

To increase the wear resistance and durability of parts, it is necessary to ensure proper roughness of the surface of the part. To achieve this goal, you can use the method of electric spark doping, which is characterized by energy intensity, environmental cleanliness and a number of other advantages. With the help of electric spark doping, both single-layer and multi-layer protective coatings can be applied, which allow you to obtain new surface materials.

Layer-by-Layer Deposition of Copper and Phosphorus Compounds to Develop Flame-Retardant Polyamide 6/Montmorillonite Hybrid Composites

Nowadays, increasing attention is devoted to the search for polymeric composite materials that are characterized by reduced flammability. In this work, the layer-by-layer (LbL) technique was applied to form multilayered protective coatings for polyamide 6/montmorillonite (PA6/MMT) hybrid nanocomposites. This time, the double layers LbL deposition was used in order to improve the thermal properties or flammability of PA6 materials. Our goal was to check how five, 10, and 15 triple-layer deposition onto the surface of PA6 and PA6/MMT composites influenced these relevant properties. For this reason, disodium H-phosphonate, sodium montmorillonite, and iodo-bis(triphenylphosphino)copper were used for polyelectrolyte solution preparation. It was found that the LbL method could be successfully used to improve the flammability characteristics of polyamide 6-based composites. Nevertheless, the deposition of the copper complex should be combined with other flame retardants—preferentially containing phosphorus—which enable synergistic effects to occur. Moreover, microscopic observations confirmed that the surfaces on which the formation of interwoven fibrous crystal structures was observed had a tendency to protect the entire material against the destructive effects of heat, contributing, among other things, to reduce the maximum point of heat release rate (PHRR).

Effect of processing conditions on the structural properties and corrosion behavior of TiO2–SiO2 multilayer coatings derived via the sol-gel method

TiO2–SiO2 multilayer protective coatings were prepared via the sol-gel method on a C45E steel substrate. The influences of the number of layers, annealing temperature and annealing atmosphere on the corrosion resistance were investigated. Electrochemical characterization showed correlations between the processing parameters and the corrosion resistance. A maximum polarization resistance of 61 kΩ cm2 was achieved with coatings of three layers annealed at 900 °C in air compared to just 2 kΩ cm2 for the uncoated C45E steel sample. This research revealed the possibility of preparing a dense corrosion-resistant layer on C45E steel with minimal surface defects by optimizing the processing parameters.

Microstructure and mechanical properties evaluation of cathodic arc deposited CrCN/ZrCN multilayer coatings

For the development of advanced nanoscale multilayer protective coatings, proper design of microstructure and chemical composition of carbon containing sequential transition metal nitride nanolayers is an important issue. In this work, five different nanostructured CrCN/ZrCN multilayer coatings were deposited periodically by cathodic arc evaporation. The bilayer period of the CrCN/ZrCN multilayer coatings was kept at 20 nm. The C2H2 gas flow ratio was adjusted from 6.3 to 20.0% for achieving CrCN/ZrCN multilayer coatings with 2.3–4.2 at.% carbon content. Nanolaminated CrCN and ZrCN nitride layers and thin amorphous carbon nitride mixed nanolayers ∼5 nm thick were obtained as the carbon content reached 4.2 at.%. It was found that the hardness and adhesion quality were strongly improved by the carbon addition to the CrCN/ZrCN multilayer coatings. An increase of 2.6–4.6 GPa in hardness was found for the CrCN/ZrCN multilayer coatings due to the balance of solution hardening effect of carbon atoms and the softening by the amorphous mixed nanolayer. An optimal combination of high hardness, 28.9 GPa, and good adhesion, 41 N of upper critical load were achieved when the carbon content was 4.2 at.% for the CrCN/ZrCN multilayer coatings.

Multilayer protective coatings obtained by pulsed laser deposition

Devices developed for the aeronautic or space industries must be able to operate in harsh environments. In order to protect devices such as microstrip antennae, various coatings have to be used. Herein, we present the results of obtaining YSZ/Al2O3 heterostructures by Pulsed Laser Deposition (PLD) for the protection of planar monopole antennas without changing their performances after the deposition process. The theoretical SRIM-TRIM simulation code results on the effects of ionized radiations incident on a YSZ/Al2O3 heterostructure, as well as the physical properties of the YSZ/Al2O3 thin films obtained by the PLD technique are also presented. The SRIM studies show that at the same energy range the proton penetration depth is higher than the alpha penetration depth, giving insights about the penetration depth of proton and alpha particles in the studied targets. Our goal is to obtain a multilayer structure able to enhance the endurance of the antenna and microwave circuitry in harsh space environment without reducing the performances under nominal operation conditions.

The heterogeneous anti-radiation shield for spacecraft*

The paper deals with modeling of elemental composition and properties of heterogeneous layers in multilayered shields to protect spacecraft onboard equipment from radiation emitted by the natural Earth’s radiation belt. This radiation causes malfunctioning of semiconductor elements in electronic equipment and may result in a failure of the spacecraft as a whole. We consider four different shield designs and compare them to the most conventional radiation-protective material for spacecraft - aluminum. Out of light and heavy chemical elements we chose the materials with high reaction cross sections and low density. The mass attenuation coefficient of boron- containing compounds is 20% higher than that of aluminum. Heterogeneous shields consist of three layers: a glass cloth, borated material, and nickel. With a protective shield containing heavy metal the output bremsstrahlung can be reduced. The amount of gamma rays that succeed to penetrate the shield is 4 times less compared to aluminum. The shields under study have the thicknesses of 5.95 and 6.2 mm. A comparative analysis of homogeneous and multilayered protective coatings of the same chemical composition has been performed. A heterogeneous protective shield has been found to be advantageous in weight and shielding properties over its homogeneous counterparts and aluminum. The dose characteristics and transmittance were calculated by the Monte Carlo method. The results of our study lead us to conclude that a three-layer boron carbide shield provides the most effective protection from radiation. This shield ensures twice as low absorbed dose and 4 times less the number of penetrated gamma-ray photons compared to its aluminum analogue. Moreover, a heterogeneous shield will have a weight 10% lighter than aluminum, with the same attenuation coefficient of the electron flux. Such heterogeneous shields can be used to protect spacecraft launched to geostationary orbit. Furthermore, a protective boron-containing and nickel coating can be deposited onto a finished housing frame of space equipment.

Novel multilayer nano-composite protective coatings for metallic medical tools

Abstract Requirements for tribological protective coatings for medical tools, which would increase their wear and corrosion resistance, are very high. The presented paper deals with novel nano-composite, multilayer protective coatings for tissue interaction elaboration and their diagnosis on metallic substrates. A hybrid pulsed laser deposition system was used for coating deposition. In the presented work, nano-composite Cr/CrN + [Cr/a-C : H implanted by metallic nanocrystals] multilayer coatings were developed for surface protection. The mechanical properties of the coatings were investigated by means of micro-hardness and elasticity modulus measurements. Bio-medical tests were conducted using eukaryotic cells. Microstructural analysis by means of transmission electron microscopy indicated that chromium which was implanted into a-C : H layers reacted with carbon forming chromium carbides.

Stressed-Strain State of Multi Layer Foil under One-Axis Tension

Multilayer protective materials and coatings attract attention last years because the possibility appears to obtain unique properties of materials due to combination of properties and sizes of layers. In his paper analytical solution is constructed for the problem on multilayer foil tension. It is assumed that stress and strain tensor components depend on one space coordinate in the axis direction perpendicular to layers and generalized plane stressed state is realized. Interesting effect is detected for two-layer material: thickness of the coating exists when one of diagonal stress tensor components is minimal, that ensure minimal break in the corresponding stresses in interface. This effect is observed previously experimentally by many authors. However, other diagonal component of stress tensor has maximal value for other value of coating thickness. The positions of the maximal and minimal values of stresses and breaks depend on combination of properties and thicknesses of layers.

Review of Home-Grown Technologies in the Field of Protection of Carbon-bearing Materials from Gaseous Corrosion and Erosion in Plasma’s High-Speed Flow

This article is continuation of authors’ publication cycle on subject «Multifunctional protective c-e for extra heat-stressed elements of structure of hypersonic systems». There was made analysis of modern domestic approaches to creation of single-ply and multilayer protective coatings of various classes: glass-ceramic, receiving by means of different methods; on the base of oxide ceramics; oxygen-free reaction-bonded; microcomposite syner- getic type. There was paid attention on full absence of applied science investigations, oriented on development of structured and physic-chemical models of coatings’ architecture, substantiation it’s functioning in the conditions of interaction with gas’ high-speed flow. Selection of coatings’ chemical composition and processing technology of its formation is realized basically on empirical base. There was presented a range of coatings, declared as workable in the still or weak perturbed air up to temperature 1600–2000 °C; however, there is not realistic estimate its protective capabilities in the conditions of impact of high entalpic ultra- and hypersonic oxygenated gas flow, owing lack or absence of appropriate data. Especially pinpointed microcomposite coatings of synergetic type Si–TiSi 2 –MoSi 2 –B–Y, developed in the frame of original conceptual approach to creation of multilevel sys- tem of heat protection of heat-stressed construction elements from heat-resisting materials of hypersonic motor apparatus and its propulsion plants. Detailed analysis of its r within single constructive wall with protected carbonaceous material allows detect trends and directions of authors’ follow- up study with the aim of development’s improvement.

New ways to the manufacturing of pigmented multi-layer protective coatings

The manufacturing of pigmented multi-layer protective coatings is the matter of the present investigation. Finely sieved Al-Mg (4.5wt.%) powders were used in combination with a phenyl-methyl silicone resin to form single or multi-layered coatings with good erosion-corrosion properties. The coatings were formed on low carbon steel by alternating a layer of resin deposited by dipping or spraying to a layer of dry metallic powders deposited by fluidized bed. Baking in convection oven at 250°C for 45min allowed the full consolidation of the composite coatings. The visual appearance of the coatings and the uniformity in them of the powder distribution were assessed by scanning electron microscopy. The favorable erosion-corrosion endurance of the developed coating systems were investigated by progressive load scratch tests, dry sliding linear reciprocating tribological tests and dipping in acid and salty solutions. In conclusion, the good protection grade the coatings are able to provide together with the viability of the manufacturing process ensure a high potential of the proposed technology in several industrial domains.

Complex determination of the diffusion coefficients of alloying elements in heat-resistant nickel alloys and deposition of multifunctional multilayer protective coatings

We showed the possibility and suggested the calculation procedure of determining the diffusion coefficients of elements in complex doped alloys from the distribution of elements in dendritic cells of heat-resistant nickel cast alloys. We developed a new technology to deposit multifunctional coatings on gas-turbine blades, which, at working temperatures, prevent the formation of undesired topologically close-packed phases in a protected heat-resistant nickel alloy and its coating for a given lifetime.

Complex determination of the diffusion coefficients of alloying elements in heat-resistant nickel alloys and deposition of multifunctional multilayer protective coatings

Complex determination of the diffusion coefficients of alloying elements in heat-resistant nickel alloys and deposition of multifunctional multilayer protective coatings

Damage Evaluation of Thermal Barrier Coatings Under High Temperature Low Cycle Fatigue Conditions

Thermal Barrier Coatings (TBCs) are multi-layer protective coatings used in the hot section components such as combustor and turbine of advanced gas turbine engines to protect them from degrading effects of hot gases. Today, due to lack of a reliable life time assessment, the potential of these coatings cannot be fully used. Understanding of damagemechanisms of thermal barrier coatings is the key factor to increase durability and reliability. In this paper TBCs have been shortly introduced and then damages resulting from high temperature low cycle fatigue tests and their probable reasons have been explained. Inconel 100, a directionally solidified nickel based superalloy as a substrate, approximately 120 μm thick NiCoCrAlY bond coat and approximately 200 μm thick 7 wt % Yttria Partially Stabilized Zirconia ceramic top coat have been used. Both layers are deposited by EB-PVD technique. The results of the tests show that number and size of the cracks changes with the strain range. Cracks initiate in the TGO/BC interface and propagate into the substrateperpendicularly to the loading axes. Ceramic thermal barrier coating retards the formation of cracks. On the surfaces of the specimens having only bond coat, rumpling which is a typical service damage of turbine blades has been detected.

Corrosion behavior of chromium-free dacromet coating in seawater

In order to overcome the environmental objection of chromium(VI) in dacromet, a novel chromium-free dacromet was developed. Electrochemical impedance spectroscopy (EIS) and d.c. potential measurements were employed to study the anticorrosion behavior of the sintered ceramic zinc–aluminum coatings in still seawater. Results of X-ray diffraction (XRD) indicate that the main corrosion products are composed of Al 2O 3, ZnCl 2, Zn(OH) 2 and Fe 2O 3. The scanning electron microscope (SEM) and energy dispersive X-ray spectroscope (EDX) analysis were carried out to study the morphological appearance and the local chemical composition of run-out coatings. The results show that the evolution of open circuit potential can be divided into four stages during the lifetime of CFD/steel. The EIS behaviors of Zn–Al coatings immersion in seawater at the first day are similar to the ceramic CrN coating prepared by PVD, while the impedance data of the next days are parallel with multilayer protective coatings. The galvanic protection effect of the coating keeps active only in the first 3 days and then the physical shielding function play a dominant role.

Multilayer protective polymeric coatings: Providing for their continuity

It has been shown that, owing to the application of a multilayer design (construction) and the correct choice of technology and materials, the following results on enhancement of the continuity of polymeric protective coatings (PCs) may be achieved: (1) a reduction in the technological defectiveness to a preassigned level due to overlapping of flaws, even at a high specific defectiveness of the materials used in the PC layers; (2) an increase in the resistance to cracking of rigid PC layers and hard substrates because of the redistribution of internal stresses in the substrate-multilayer PC system; and (3) an enhancement in PC resistance to cracking on the opening-up of a crack in the substrate under tension of bending.

Investigation of temperature and stress fields in laser cladded coatings

Temporal and spatial distributions of temperature and strain–stress have been modelled and investigated experimentally for the laser cladding process. The model corresponded to experimental conditions where the multilayer protective coatings were prepared by direct laser cladding of stellite SF6 powder on X10Cr13 chromium steel by means of a 1.2 kW CO 2 laser. For calculations the effect of base preheating, temperature dependent material properties, and also influence of time-break between cladding of the consecutive layers were taken into account. The calculated temperature fields indicated good bonding of the substrate and coating, which was in agreement with the micro-analytical test results. A decrease of the number of microcracks in the coating with an increase of substrate preheating temperature was concluded from stress calculations and confirmed in the experiment. Moreover, an increase of the cracking susceptibility with an increase of the time delay between cladding of the consecutive layers was evidenced by modelling. The best technological results were obtained for the case of single-layer coatings prepared on a preheated substrate and for higher coating thickness required the processing of consecutive layers with a possibly short time delay is advisable due to effective usage of laser beam energy for preheating and lower temperature gradients.

Advanced Graded Protective Coatings, Deposited by EB-PVD

Electron beam technology (EB-PVD) and equipment for one-stage deposition of advanced graded protective coatings using a composite ceramic ingot for evaporation are described. This technology allows replacing the flat interface between coating layers by a graded transition zones and achieve of a high degree of reproducibility of the composition, structure and lifetime of the functionally graded coating in compare with traditional multi-stages technologies of protective coating deposition.A design of the composite ceramic ingot is considered, as well as the ability to regulate in a broad range the composition, structure and properties of all levels of the graded protective coating including transition zones and coating layers. Examples and variants of advanced graded protective coatings with their structures and properties are given (thermal barrier, hard erosion-resistant and damping coatings) for aerospace and gas-turbine industry application deposited by one-stage EB-PVD process. Total cost of one-stage EB-PVD deposition process at least 2 times less in compare with traditional technological processes of protective coating deposition due to using only one EB-PVD unit and elimination of multistage nature of process cycle.Laboratory and productive electron-beam units designed and manufactured at ICEBT are considered. Development of modern protective coatings, technologies and equipment for their application is focused, primarily, on improvement of the durability and main service properties of the coating/protected item system, ensuring a reliable reproducibility of the coating structure and properties, shortening the cost and time of the entire technological cycle of their deposition. The existing traditional technologies of deposition of multilayer protective coatings, for instance, thermal barrier coatings (TBC), containing a oxidation-resistant metal bond coat and outer low thermal-conducting ceramic layer, are multi-stage, with combination of such processes as diffusion saturation, galvanic coating, plasma spraying and electron beam deposition [1-3]. Use of diverse expensive equipment, availability of intermediate mechanical and thermal treatments, as well as the operations of surface cleaning, apply considerable limitations both on widening of the sphere of such coating application, and their further development in terms of improvement of the structure and properties. The one-stage electron beam technology developed at ICEBT for deposition of advanced protective coatings based on evaporation of a composite ingot and allowing deposition of functionally graded coatings in one process cycle, meets the above goals to a considerable extent [4,5]. The technology is based on the use of the known phenomenon of fractionating at evaporation of multicomponent systems, containing elements with different melting temperature and vapour pressure, and their subsequent condensation under vacuum, allowing the flat interface, for instance between the metal and ceramic layers, to be replaced by a transition zone of the graded composition and structure. Fig.1 gives the schematic and appearance of a composite ingot used for one-stage deposition of advanced graded protective coatings in vacuum by its electron beam evaporation from one crucible. The ingot base material determines the purpose of the graded coating. For instance, Al2O3, TiC, TiB2, B4C, MgO, etc. can be used as the base of the ingot for deposition of hard wear-resistant, erosion-resistant and damping coatings. For the case of TBC, this is zirconium dioxide with additives