Composite Coatings Research Articles

RESEARCH OF HEAT RESISTANCE OF CARBON-CARBON COMPOSITE MATERIALS WITH PROTECTIVE COATINGS OBTAINED USING FUNCTIONALLY ACTIVE CHARGES

This study focuses on the development of protective coatings for carbon-carbon composite materials (CCСM) used in high-temperature processes in aerospace engineering. CСCM have limitations due to their susceptibility to oxidation, erosion, and burnout in gas streams. Our research is aimed at creating protective coatings using functionally active charges (FAC) obtained under non-stationary temperature conditions and improving the performance of composites. The aim of our study is to identify the optimal compositions of powders for chromium-alloyed protective coatings using functionally active charges to increase the heat resistance of the working surface. We analyzed various methods of obtaining protective coatings, including chemical-thermal and liquid-phase saturation methods, to find out their peculiarities in interaction with the CCСM matrix and changes in their mechanical properties. In addition to the traditional methods, we have investigated the method of saturating the surface with a solid phase in an active gas environment using FAС, which are obtained under non-stationary temperature conditions. This method provides high quality coatings, reduces processing time and makes it possible to work at high temperatures depending on the composition of the spray coatings. Much attention was paid to the problem associated with chemical interaction and formation of carbide phases, which are important for ensuring the stability of coatings under high temperature conditions. Experimental studies include a factorial experiment to determine the compositions of powder mixtures that provide high heat resistance. Various independent variables, such as the content of chromium, silicon, titanium, and aluminum, were considered, taking into account their influence on the physical and mechanical properties of coatings. Particular attention was paid to the optimization of the parameters of thermal autoinitiation of the functionally active charge under process conditions. Regression equations are presented to evaluate the dependence of the wear resistance of coatings on the autoinitiation parameters and the content of alloying elements. The analysis of the study results includes the construction of three-dimensional graphical dependencies for optimizing the composition of powdered CBA in the Cr-Al-Ti and Cr-Al-Si systems. In practice, chromium-aluminum-siliconized coatings obtained under isothermal conditions, when tested for heat resistance, have a more porous surface through which oxygen penetrates to the surface of the HCCM. Compared to the coatings obtained using FAS, the heat resistance is 1.5-1.7 times higher, which can be explained by the higher concentration of chromium, aluminum, silicon, and titanium, which contribute to the formation of protective oxide membraness. The low-porosity surface of the coatings obtained using functionally active layers prevents oxygen from entering the material, contributing to the formation of oxide protective membranes such as SiO2, TiO2, Cr2O3, Al2O3.

Oleogel Microsphere‐Based Composite Protective Coatings with Room‐Temperature Self‐Healing Enabled by a “Soft + Hard” Hybrid Architecture

AbstractIntrinsically self‐healing coatings are compelling candidates for highly reliable anti‐corrosion technologies because of their easy implementation, low cost, and repeatable self‐healing. However, most of these coatings require intervention to initiate healing due to the locking of their chain segments under ambient conditions (to provide sufficient mechanical strength). Herein, a “soft + hard” hybrid architecture strategy of preparing oleogel‐based protective coatings with room‐temperature and repeatable self‐healing is proposed by embedding “soft” self‐healing and viscoelastic oleogel microspheres (OMs) in “hard” waterborne epoxy matrix. Such a decoupled design affords both instantaneous healing without external stimuli (crack narrowing within 10 min and protection recovered within 5 h) and good mechanical properties (improved wear resistance with an 80% reduction in friction coefficient, a 63% reduction in wear volume, as well as a maintained adhesion strength of 96%). The slippery and hydrophobic OMs also bring anti‐biofouling, interfacial water repellency, and inhibitor loading‐release features, leading to coatings with superior corrosion protection (>1010 Ω cm2 impedance modulus throughout 110 d) rather than just their self‐healing. This work demonstrates a feasible approach to integrating room‐temperature repeatable self‐healing and sufficient mechanical strength in future coating design.

Mesoscopic characteristics, microstructure evolution, friction mechanisms, and corrosion behavior of Ni60-SiCp coatings fabricated by laser-based directed energy deposition

The influence of varying SiCp on the mesoscopic characteristics, microstructural evolution, microhardness, frictional mechanisms, and corrosion resistance behavior of laser-based directed energy deposition Ni60-SiCp composite coatings was investigated. Coatings reinforced with varying SiCp, the innovative concept of the ''Temperature-SiCp joint effect'' mechanism was proposed. The microstructure was progressively refined due to the SiCp, while microhardness was affected by the solid solution strengthening and diffusion strengthening effects of high SiCp. Furthermore, based on wear scar morphologies, wear scar EDS analysis, and wear mechanism modeling, the frictional mechanisms were elucidated. Simultaneously, a clear understanding of the relationship between SiCp and corrosion behavior were established. It is evident that the analysis of SiCp reinforcement content in composite holds significant guiding significance.

Implementing All-Weather Photocatalysis of Exhaust Fumes Based on the g-C3N4/TiO2/SrAl2O4: Eu2+, Dy3+ Ternary Composite Coating

This study examines the use of SrAl2O4: Eu2+, Dy3+ long-afterglow materials doped into g-C3N4/TiO2 coatings for photodegradation. The prepared sample was tested for the purification of automotive exhaust fumes, with the optimal mass ratio of g-C3N4/TiO2 and SrAl2O4: Eu2+, Dy3+ determined to be 1:1. Characterization tests, including XRD, FT-IR, XPS, and TG-DSC, were conducted to evaluate the microstructure and properties of the samples. Under poor lighting conditions, g-C3N4/TiO2 reduced CH and NOx by 59 ppm and 13 ppm within 4 h, respectively, while g-C3N4/TiO2/SrAl2O4: Eu2+, Dy3+ decreased CH and NOx by 98ppm and 34ppm, respectively, resulting in a significant improvement in degradation efficiency. The addition of long-afterglow materials significantly improves the efficiency of photocatalysts in purifying exhaust fumes in low-light environments, providing potential value for all-weather exhaust treatment in the future.

The effect of laser textured resin surface on the adhesion of supersonic plasma sprayed Al2O3/PF composite coating

Polymer composite materials have rapidly developed due to their unique properties and economic advantages. Despite their prominent physical and mechanical properties, they are unable to meet the higher performance targets in certain exceptional circumstances. Thermal sprayed ceramic/resin composite coating is a feasible solution. Prioritizing the mechanical properties of coating is significant theoretical and scientific value in practical engineering applications. In the article, Al2O3/phenolic resin composite coatings on the textured and sandblasted surface of the glass fiber reinforced polyester are prepared by supersonic plasma spraying. The damage of laser processing periods on resin substrate was discussed. The effect of pit depth and pattern interval on the bonding strength of coating was deeply explored. The results reveal that the highest bonding strength of the coating on textured surface is 28.4 MPa, which is double that of the coating on sandblasted surface. The textured surface can be effectively created with appropriate laser process parameters while avoiding the damage of fiber. On the premise that the glass fiber is not damaged, deeper pits and smaller pattern interval are beneficial for increasing the contact rate between the coating and the substrate. The research provides an effective way to dramatically increase the adhesion of the ceramic/resin composite coating.

Production of Cu/Diamond Composite Coatings and Their Selected Properties.

This article presents Cu/diamond composite coatings produced by electrochemical reduction on steel substrates and a comparison of these coatings with a copper coating without diamond nanoparticles (<10 nm). Deposition was carried out using multicomponent electrolyte solutions at a current density of 3 A/dm2 and magnetic stirring speed of 100 rpm. Composite coatings were deposited from baths with different diamond concentrations (4, 6, 8, 10 g/dm3). This study presents the surface morphology and structure of the produced coatings. The surface roughness, coating thickness (XRF), mechanical properties (DSI), and adhesion of coatings to substrates (scratch tests) were also characterized. The coatings were also tested to assess their solderability, including their spreadability, wettability of the solder, durability of solder-coating bonds, and a microstructure study.

Effect of the graphene-based material on the conductivity and corrosion behaviour of PTFE/graphene-based composites coatings on titanium for PEM fuel cell bipolar plates

Titanium is widely used as a material for bipolar plates (BP) PEM fuel cells, but they require conductive coatings that help with corrosion and have low interfacial contact resistance (ICR). Among many materials, polymer composites reinforced with graphene nanoparticles have the potential to become an effective coating, but the influence of different types of graphene-based materials on the performance remains has not been properly established. In this study, different nanoparticles (graphene monolayers, reduced graphene oxide and few-layer graphene) were used to process PTFE/graphene composite coatings for Ti, and their performance was evaluated. Most of the coating formulations improved the corrosion resistance of the Ti in one or two orders of magnitude, but only the combination of few-layer graphene and carbon black as additive resulted in an ICR of 12 mΩcm2, in range with the target values.

Effect of Heat‐Treatment and NiB–TiO2 Composite Coating on the Tribological Performance of AISI P20 Steel

Effect of Heat‐Treatment and NiB–TiO₂ Composite Coating on the Tribological Performance of AISI P20 Steel

Effect of SiC fillers on the microstructure, adhesive strength and corrosion resistance of polycarbosilane-derived coating on steel

Polycarbosilane-derived (PCS-derived) coating containing SiC fillers with enhanced adhesive strength and corrosion resistance were fabricated on Q235 steel by a simple method of dip coating. The effects of content and particle size of SiC fillers on the phase composition, surface morphology, adhesive strength and corrosion resistance of PCS-derived coatings were studied. Addition of SiC fillers could reduce the microcrack width on the coating surface. The microcrack width decreases with the decrease in particle size of SiC fillers. Addition of 2.5 wt% SiC fillers with particle size of 30 nm could make the coating surface crack-free. Different from particle size, the effect of filler content on the microcracks has a moderate value which is corresponding to lower microcrack width. In addition to the microcracks, SiC filler content and particle size have significant effects on the adhesive strength between coatings and substrates. The higher adhesive strength is 319.1 MPa for coatings fabricated with a particle size of 500 nm and a content of 10 wt%. SiC fillers can improve the corrosion resistance of the PCS-derived coatings. In comparison with particle size of filler, filler content has a greater effect on the corrosion resistance of the coatings. The corrosion mechanism was analyzed. Appropriate content of fillers reduce the microcrack width and further improve the corrosion resistance of the coatings.

Green based composite polyurethane coatings for steel

Green based composite polyurethane coatings for steel

Microstructure and wear resistance of SiC strengthened laser cladded Inconel625-Nb4-SiCx composite coatings

The Inconel625-Nb4-SiCx composite coatings with SiC content ranging from 0 to 2.4 wt% were fabricated through the laser cladding technology. The microstructure of the coating was characterized and the properties of the coating were fully tested. The addition of SiC promoted the generation of M(Nb, Mo)C and Cr23C6 in the coating and improved the homogeneity of the microstructure. The microhardness distribution of the samples could be divided into four zones in order: substrate, heat affected zone, fusion zone and coatings. Similarly, the microhardness of the coatings gradually improved as the SiC content increased, and 2.4SiC coating obtained the highest microhardness, which was 58.2 % above the substrate. The friction test results indicated that the increasing SiC had a constructive impact on the friction performance of the coatings, namely, the wear rate of the coatings was decreased over the substrate by 20.7 %, 36.7 %, 44.6 %, 60.1 % and 70.1 % in order. The wear mechanism shifted from grievous adhesion, oxidation, and fatigue wear in the substrate to mild adhesion and oxidation wear in 2.4SiC coating. This work investigated SiC enhanced In625/Nb/SiC composite coatings and provided a new solution for repairing and improving the performance of In625.

Numerical simulation of thermal evolution and grain morphology of laser melted AlSiTiNiCo-WC composite coatings

Numerical simulation of thermal evolution and grain morphology of laser melted AlSiTiNiCo-WC composite coatings

Influence of electrodeposition parameters on the fabrication of Ni–Co/SiC + TiN composite films through pulse current electrodeposition

In this investigation, pulsed current electro-deposition (PCE) was used to prefabricate Ni–Co/SiC + TiN composite coatings (NCSTCCs) on mild steel surfaces. The research focused on the influence of two electrodeposition parameters, pulse frequency (PF) and duty cycle (DC), on NCSTCF features including microscopic surface morphology, crystal orientation, grain size, microhardness, SiC and TiN nanoparticles (NPs), deposition quantity, and corrosion resistance properties. The results indicated that NCSTCCs produced under a 10% DC showed minimal SiC and TiN contents with a percent volume of just 5.6 v/v% and 5.4 v/v% respectively under the fixed condition of 60 Hz PF. However, the three-dimensional surface diagram indicated that the Ni–Co/SiC + TiN composite film deposited at 50% DC and 10 Hz PF displayed the highest SiC and TiN contents (11.6 v/v% and 11.7 v/v%) among all the films. Furthermore, NCSTCCs deposited under 50% DC and 10 Hz PF had peak microhardness at 667.4 kg/mm2, while the composite film achieved a microhardness of 514.1 kg/mm2 when prepared using 10% DC and 60 Hz PF. Moreover, when the DC and PF were at 50% and 10 Hz respectively, the Ni–Co/SiC + TiN composite film presented the maximum charge transfer resistance (4915.7–4927.2 Ω·cm2), indicating an excellent corrosion resistance.

Influence of Cu distribution in thermally sprayed Cu-bearing coatings on the prevention of Desulfovibrio vulgaris corrosion

Thermally sprayed Cu-based coatings show promise for combating microbiologically influenced corrosion (MIC) within natural gas pipelines. However, the efficacy of Cu-bearing coatings against MIC over prolonged exposure to bacterial fluids remains unclear. To examine the effect of Cu distribution on the prevention of MIC, two types of Cu-containing coatings were prepared: stainless steel (SS)-Cu composite coatings and Monel 400 coatings with Cu in solid solution. These coatings were deposited using high velocity oxy-fuel (HVOF) and wire arc spray (WAS) techniques. Dynamic flow corrosion testing was utilized to examine the influence of Cu concentration and distribution on biofilm attachment and pit formation. The results show that SS-Cu composite coatings exhibit preferential Cu dissolution when exposed to Desulfovibrio vulgaris solution, significantly reducing biofilm attachment over the short-term period (7 days) which correlated with the release rate of Cu ions. However, accelerated Cu ion release led to Cu2S deposition on sample surfaces, diminishing anti-biofilm properties with prolonged exposure (28 days). Pit depth measurements indicated a correlation between pit formation and Cu ion release throughout the exposure period, with bio-generic H2S likely contributing to increased pit corrosion. Utilizing the Preference Ranking Organization Method for Enrichment Evaluation (PROMETHEE), the anti-MIC performance of coatings were ranked based on biofilm thickness, biofilm coverage, pit depth, antimicrobial effect, and splat thickness. The ranking placed WAS Monel with Cu in solid solution as the most effective coating, attributed to its thin laminar structure, enhanced corrosion resistance, and antimicrobial properties. Cu in solid solution was concluded to be more effective in resisting MIC of Desulfovibrio vulgaris under dynamic flow conditions compared to Cu existing as segregated phase within composite coatings.

Electric-field-induced assists fabrication of micro-SiC/Epoxy coating with low additive amount to improve surface insulating performance of HVDC insulator

The micro-SiC/Epoxy composite coating has huge potential for application in the insulator of high voltage direct current (HVDC) gas insulated switchgear (GIS) since it can effectively suppress charge accumulation at gas–solid interface and adaptively regulate resistive electric field distribution. However, achieving stable and fruitful properties often requires high filler concentrations, which can compromise processability and long-term stability. Thus, a new method is proposed for preparing SiC/Epoxy composite coatings based on in-situ electric-field-induced assist (EFIA). The alignment process of SiC induced by the in-situ electric field, the effects of in-situ field on the physical and chemical properties of cured composites were studied. Even at concentrations far below the percolation threshold, the alignment of SiC particles along the in-situ electric field direction can induce significant non-linear conductive properties along that specific direction in the composite. Furthermore, the EFIA-coating leads to a 59.43% reduction in surface charge accumulation, more than a 50% decrease in charge dissipation time, and a 17.3% increase in surface flashover voltage. The coating discussed in this paper will be helpful in insulation design of DC components.

Fabrication of CNTs/MMT/PPS composite hydrophobic coatings on metal with enhanced anticorrosive and self-cleaning performance

Although much work has been reported on anticorrosive coatings at this stage, most materials are confronted with a variety of harsh environments in practical applications, posing extreme challenges to the various properties of the coatings. In this study, carbon nanotube/montmorillonite/polyphenylene sulfide (CNTs/MMT/PPS) composite coatings were prepared by air spraying method. CNTs-MMT composite fillers with nanostructures were prepared by the amide reaction of 3-aminopropyltriethoxysilane (APTES) modified MMT and carboxylated CNTs. The particle size distribution test demonstrated that the amidated CNTs-MMT exhibited superior dispersion performance compared to CNTs and MMT alone, resulted in a more homogeneous and dense coating. The coatings obtained by combining the low surface energy of polytetrafluoroethylene (PTFE) exhibits hydrophobicity and has excellent self-cleaning properties. The electrochemical corrosion current density of the composite coating was three orders of magnitude lower than that of bare iron, and the corrosion efficiency was 99.43 %, demonstrating excellent corrosion resistance. The thermogravimetric test results showed that the CNTs/MMT/PPS composite coatings displayed excellent thermal stability up to 530 °C. Therefore, the CNTs/MMT/PPS composite coating possesses significant advantages in the field of anti-corrosion due to its enhanced durability, heat resistance, and corrosion resistance.

Inhibition Mechanism of Water-Soluble Chitosan-Curdlan Composite Coating on the Postharvest Pathogens of Serratia marcescens and Pseudomonas syringae in Cherry Tomatoes.

Cherry tomatoes, a very popular fruit, are highly susceptible to microbial infestation, which cause significant economic losses. In order to preserve cherry tomatoes better, we treat them with a Chitosan (CTS) and Curdlan (CUR) composite coating. The lowest inhibitory concentration of CTS/CUR composite coating on Serratia marcescens and Pseudomonas syringae, the growth curves, and the changes of the cell lysis rate were determined to explore the inhibitory mechanism of CTS/CUR composite coating on Serratia marcescens and Pseudomonas syringae and the microscopic morphology of Serratia marcescens and Pseudomonas syringae was observed using scanning electron microscopy at the same time. The results showed that the CTS/CUR composite coating could effectively inhibit the growth of Serratia marcescens and Pseudomonas, and the inhibitory effect reflected the concentration-dependent characteristics. The electron microscopy results indicated that the inhibition of Serratia marcescens and Pseudomonas syringae by the CTS/CUR composite coating might originate from its disruptive effect on the cell wall and cell membrane of the bacterium.

Bacterial and corrosion resistance of polytetrafluoroethylene-silver composite coatings by magnetron sputtering

Titanium alloy and stainless steel implants have been widely applied in orthopedics. However, harmful ions released from implant corrosion caused by human body fluids and bacterial infections may inhibit patients’ recovery. In this work, a polytetrafluoroethylene-silver composite coating was prepared by RF unbalanced magnetron sputtering to improve the bacterial and corrosion resistance of the SS316L. The removal rates of the composite coatings for Escherichia coli and Staphylococcus aureus reached 97.27% and 99.99%, respectively. The contact angle of 131.5° and fluorescence staining experiments show that the composite coating has an antiadhesive effect on bacteria and less cytotoxicity against osteoblasts. The corrosion voltage of the composite coating was much higher than that of the control SS316L substrate, and the corrosion current density was reduced to 1/3, implying the enhancement of the corrosion resistance of the SS316L substrate.

In Situ Thermal Interactions of Cu-Based Anti-Corrosion Coatings on Steel Implemented by Surface Alloying

Incorporating expensive alloying elements into bulk steel for corrosion protection is undesirable, considering that only the surfaces are exposed to aggressive environments. Therefore, this work focused on developing and optimizing a new surface functioning technology through in situ observation of thermal interactions between the metallic powders at elevated temperatures. The study revealed that the Cu-Ni powder mixture, with 12.5 wt% Ni, began to melt at 1099.5 °C and was fully melted at 1175 °C, significantly different from the Cu-Ni solid solution and bulk Cu or Ni. As a result of high-temperature reactions, copper penetration of up to 35 µm for pure copper and 55 µm for copper-chromium composite coatings occurred due to liquid metal corrosion. In contrast, the copper-nickel composite coating exhibited a cupronickel solution microstructure with FeNi dendrites and a nickel-rich transition layer. This cupronickel coating, with a chemical composition of 89.3 wt% Cu, 6.2 wt% Ni, and 4.5 wt% Fe, demonstrated uniform thickness, superior surface morphology, and continuous coverage on the steel substrate. Furthermore, the Ni-rich transition layer played a vital role in preventing copper penetration along the grain boundary of the steel matrix while forming a chemical binding between the coating and the substrate. The practicality of the coating was further confirmed through the hot-rolling procedure and subsequent electrochemical corrosion tests, which resulted in a 44% improvement in corrosion resistance.

Empowering Photovoltaic Panel Anti-Icing: Superhydrophobic Organic Composite Coating with In Situ Photothermal and Transparency.

Solar energy is widely used in photovoltaic power generation as a kind of clean energy. However, the liquid film, frosting, and icing on the photovoltaic module seriously limit the efficiency of photovoltaic power generation. We developed a composite coating (Y6-NanoSH) by combining an in situ photothermal and transparent Y6 organic film with a nanosuperhydrophobic material. The Y6-NanoSH coated glass exhibited excellent optical clarity both indoors and outdoors, indicating that the coating holds great promise in anti-icing applications for photovoltaic panels. The Y6-NanoSH coating absorbs very little visible light but instead absorbs in the near-infrared region, thereby emitting heat. When exposed to sunlight, the Y6-NanoSH coated photovoltaic panel raises its surface temperature, inhibiting the growth and accumulation of ice and frost on its surface. This is achieved through a combination of photothermal emission and superhydrophobic repellency, which promotes the evaporation and rolling away of water droplets. This validates our success in developing a photothermal, transparent, and superhydrophobic coating with excellent anti-icing capabilities, suitable for use on photovoltaic panels, as well as potential applications in car windscreens, transmission lines, curtain walls, and weather radomes.