Composite Coatings Research Articles

Surface Modification of Ti-6Al-4V Alloy by Composite Coating of Polycaprolactone Nanofibers-Fluoroapatite Nanoparticles Doped with Silicon and Magnesium

The purpose of this research was to create polycaprolactone nanocomposite coating - fluor apatite nanoparticles doped with silicon and magnesium, as well as polycaprolactone coating on the alloy in order to improve and modify the biological properties of this alloy. For this purpose, nano composite coating and polycaprolactone coating were first created by immersion methode. Then the physical, corrosion and biological properties of the coating created by different methods were investigated. The results indicated the creation of a uniform nanocomposite coating with a thickness of about 6.26 micrometers, with appropriate structure and phases, and an increase in roughness by adding nanoparticles to the polycaprolactone coating. Electrochemical measurements Ti<sub>6</sub>Al<sub>4</sub>V showed that the sample coated with polycaprolactone with nanoparticles has polarization R<SUB>P</SUB>=5.349×10<sup>5</sup> Ωcm<sup>2</sup> resistance, which is higher than the sample coated with caprolactone with polarization resistance R<SUB>P</SUB>=1.191×10<sup>5</sup> Ωcm<sup>2 </sup>and the sample without coating with polarization resistance R<SUB>P</SUB>=5.2453×104 Ωcm<sup>2</sup>. Cytotoxicity test showed the non-cytotoxicity of the coatings. Also, the cell growth and proliferation of the sample with nano composite coating compared to the sample without coating has a statistically significant difference. Cell adhesion on the sample with nanocomposite coating was also much better than the sample without coating and the sample with polycaprolactone coating.

Response of variation of electrical control parameters to coatings prepared in organo-silicon electrolyte by plasma electrolytic oxidation

This study aims to explore the influence of control parameters from the perspective of the amorphous ceramic coating formation process. Three preparation processes were preferred based on the thickness, appearance and corrosion resistance of the coatings by orthogonal experiment. The surface morphology, cross-sectional structure, phase composition and micro-hardness of PEO coatings were examined using scanning electron microscopy (SEM)/Energy dispersive X-ray spectroscopy (EDS), X-ray diffractometry (XRD) and hardness measurement techniques. Findings indicate that voltage exerts the most significant impact on coating thickness and appearance, whereas the influence of other parameters becomes more pronounced as the voltage increases. Three amorphous ceramic coatings prepared in 20 min with thicknesses of 27.4 μm, 83.2 μm and 193.3 μm increased the surface hardness of 6061 aluminium alloy by 6–8 times, and decreased the corrosion current density of 6061 aluminium alloy by 3 orders of magnitude in 1 mol L−1 HCl solution. Moreover, the thickening of the coating primarily occurs within a few minutes after the voltage reaches its peak, and high frequency and low duty ratio are prerequisites for better appearance under higher voltage conditions.

Investigation of Corrosion Behavior of Cenosphere reinforced Iron Based Composite Coatings

In the present study cenopshere was reinforced with FeCrNiC (Metco 42C) as matrix material and prepared four different feedstock powders such as FeCrNiC+0%Cenosphere, FeCrNiC+5%Cenosphere, FeCrNiC+10%Cenosphere and FeCrNiC+15%Cenosphere were coated by plasma spray technique on T22 substrate. Evaluation of the substrate and coatings potential under salt spray test was performed. Dense fog of 5% NaCl salt water was used to create a corrosive atmosphere within the chamber. The salt water's pH was kept constant at 6.5-7. The materials that underwent corrosion were examined using X-ray diffraction (XRD), and scanning electron microscopy (SEM). The FeCrNiC+15%Cenosphere and FeCrNiC+10%Cenosphere coatings exhibited reduced weight loss during a 168-hour corrosion test compared to the FeCrNiC+5%Cenosphere, FeCrNiC coatings, and substrate. The excellent chemical stability and corrosion resistance of Cr23C6, SiO2, NiO, and Cr2O particles contribute to gradually avoid the formation of red rust on Fe-based coated samples with exposure approaches to 52 and 130 hours.

Multifunctional electroless nickel boron composite coatings incorporated by magnesium diboride ceramic particles

Multifunctional electroless nickel boron composite coatings incorporated by magnesium diboride ceramic particles

Microstructure, wear and corrosion resistance of Ni-based composite coating by multi-layer laser cladding

Using laser cladding technology to prepare coatings on the gear ring of the main wheel made of ZG42CrMoA, the composite coatings consisting of γ-Ni, M23C6, Ni3B, WC, and W2C. As the amount of WC nanoparticles increased, a "pinning" effect on dislocations hindered dislocation movement during wear, Comparative analysis showed a reduction in wear rate by 76.94 % and 72.80 % compared to the untreated substrate and high-frequency quenched substrate, respectively. Further, finite-element analysis indicated maximum compressive stress values of 274.37 MPa and 262.20 MPa during the impact and friction phases, respectively. This was lower than the corresponding values of the high-frequency quenched layer, which were 288.63 MPa and 283.16 MPa. The corrosion current density of the composite coating reduced by 87.98 % and 92.71 % compared to the untreated substrate and the high-frequency quenched substrate, respectively. Additionally, the electrochemical impedance amplitude of the composite coating was 72,456 Ω, which was substantially higher than that of the high-frequency quenched substrate (1270 Ω) and the untreated substrate (1717 Ω) by 570.5 % and 422.0 %.

Wear behavior of electron beam remelting modified Ni/WC thermal spray coatings

Ni/WC composite coatings were prepared by combining thermal spraying and electron beam remelting. Characterization methods such as SEM, EBSD and XRD were used. The effect of electron beam remelting beam current on the corrosion and wear resistance of Ni/WC composite coatings was investigated. The microstructure showed that hard carbides and borides such as W2C, Cr23C6, and M3B were generated within the remelted coating. Compared to the thermal spray specimens, the hardness of the 16 mA specimen was increased by a factor of 1.47, and the hardness of the 22 mA specimen was also increased by a factor of 1.14. The results of the corrosion experiments showed that the 16 mA specimen had the lowest corrosion current density and the highest corrosion potential, which showed the best corrosion resistance. Wear experiments were carried out by using SiC balls as the counterbodies. The results showed that the wear resistance of both 16 mA and 22 mA specimens under dry friction with 3.5 % NaCl solution conditions was improved compared to the thermal spray coating. The 22 mA specimens showed more obvious subsurface damage. The wear mechanism of thermal spray coatings is mainly abrasive, and the wear mechanism of remelted coatings is mainly abrasive and adhesive.

Application of bio-based modified graphene oxide in epoxy composite coatings

This study focuses on the application of bio-based modified graphene oxide epoxy composite coatings and analyzes the coating properties, such as anticorrosive ability, hydrophobicity and self-healing properties, through experimental studies of modified graphene oxide using substances such as cashew nut phenol, lignin and glutamic acid. Summarizing the latest research progress, it is found that the materials such as cardanol, lignin and glutamic acid are from a wide range of sources, are green and have a wide range of application prospects, and it is also shown in the results of EIS analysis that the modified graphene oxide epoxy compliant coatings exhibit higher impedance values at low frequencies, and have good protective properties and barrier properties. The cashew phenol-modified graphene oxide epoxy coating has high densification, high barrier capacity and high hydrophobicity in addition to good coating healing ability using GO modification. The glutamate-modified graphene oxide epoxy coating can be desorbed by using HCL solution to make L-Glu/GO reusable, with good reusability and high application value.

Composite Coatings of Gellan Gum and Inulin with Lactobacillus casei: Enhancing the Post-Harvest Quality of Guava

Guava is a highly sought-after tropical fruit in the market due to its high content of vitamins, minerals, antioxidants, and other phenolic compounds. However, due to its climacteric nature, it has a short post-harvest shelf life. The aim of this study was to develop coatings based on gellan gum (GG) and inulin (IN) incorporating Lactobacillus casei, which were tested for their potential ability to extend the post-harvest shelf life of whole guava fruit. The coatings were prepared using the following formulations: 0.5 GG/1.0 IN (w/v), 0.8 GG/5.0 IN (w/v), 0.5 GG/1.0 IN(w/v), and 0.8 GG/5.0 IN (w/v). The coated and uncoated (control) fruits were stored at 25 °C for 12 days, and various quality attributes were evaluated (including respiration rate, soluble solids, titratable acidity, weight loss, total phenol content, and color). The results indicated that the application of the coatings reduced weight loss, color change, and respiration rate in the fruits. However, the 0.8 GG/5.0 IN (w/v) formulation provided the best maintenance of post-harvest quality for the fruit evaluated. The coatings with a higher inulin content showed the highest growth of L. casei, which could enhance the antimicrobial effect of the coating. Therefore, the combined application of L. casei and inulin in coatings based on gellan gum can be considered an effective treatment to extend the shelf life and preserve the quality of guava fruits.

Air Foil Thrust and Journal Bearing Coatings: A Review

Abstract Surfaces of air foil thrust and journal bearings in high-speed turbomachinery are coated to improve their operational integrity, particularly when the aerodynamic load-carrying capacity is reduced during instances of startup and shutdown. Surface coatings, as protective barriers in air foil bearings, can mitigate the adverse effects of direct surface interactions on such occasions. This article provides an in-depth review of the body of important research conducted for the study of coated air foil thrust and journal bearings, highlighting the state of the art in coating technology. The review features the role of composite coatings, designed to provide favorable thermal, mechanical, and frictional characteristics. This article also highlights the trends in the selection of coatings for air foil bearings, pertinent to desired thermo-mechanical performance.

Effects of Cr3C2 addition on microstructure and corrosion properties of Cr3C2/15–5PH composite coatings on 12Cr13 by laser cladding

The application of laser cladding technology to prepare iron-based composite coatings has significant advantages in improving the surface properties of 12Cr13 stainless steel. 15–5PH composite coatings reinforced with Cr3C2 particles of different contents (0–25 wt%) were prepared on the 12Cr13 surface by the coaxial powder feeding laser cladding system. The microstructure, phase composition, element distribution, corrosion resistance and corrosion mechanism of the composite coatings were analyzed and studied by optical microscope, scanning electron microscope, X-ray energy dispersive spectrometer, X-ray diffractometer and electrochemical workstation. The results indicated that the Cr3C2/15–5PH composite coatings exhibited good macroscopic morphology and dilution rate under appropriate laser cladding process parameters. The addition of Cr3C2 particles changed the main phase from α-Fe to γ-Fe and formed new carbide phases (M7C3 and Cr23C6). The Cr3C2/15–5PH composite coatings exhibited a typical microstructure with rapid solidification characteristics, and the addition of Cr3C2 significantly changed the grain size. The distribution of Fe, Ni, and Cr elements in the composite coatings was uniform, and the relative content of Cr elements increased and remained at high level. The 15-5PH composite coating with 15 wt% Cr3C2 exhibited a lower corrosion current density and higher impedance modulus values. The surface of this composite coating had no obvious corrosion pits, and the passive film effectively retarded the further corrosion by the Cl- ions on the surface during the electrochemical corrosion process. By preparing a 15–5PH composite coating with 15 wt% Cr3C2 on the surface of 12Cr13, the corrosion resistance of the surface can be effectively improved.

Microstructure and Tribological Properties of WC/Ni-MoS2 Titanium-Based Composite Coating on TC4

To improve the mechanical properties of a TC4 surface, TC4 + Ni-MoS2 + xWC (x = 5%, 10% and 15% wt.%) composite coatings were prepared by the coaxial feeding laser cladding technique, and the effect of the WC content on the microstructure and tribological properties of the coatings were investigated using multiple characterization methods. The results indicated that increasing the WC content negatively impacted the forming quality of the coating, but did not change the coating phase which predominantly comprised Ti2Ni, Ti2S, TiC, matrix β-Ti and residual WC. With the addition of WC, TiC exhibited an increase in both quantity and particle size, accompanied by a transition in growth morphology from spherical to petal-like. MoS2 completely dissolved in all coatings and the S element provided by it effectively synthesized a strip-like phase Ti2S which presented a morphology similar to the lubricating phase TiS in the Ti-based melt pool system. The microhardness and wear-resistance of all the coatings were higher than that of TC4 and gradually improved with the addition of WC, which indicated that raising the WC content was conducive to enhancing the mechanical properties of the coatings. The friction coefficient of TC4 was lower than that of the three WC content coatings, indicating that Ti2S was not the lubricating phase. The wear mechanism of all coatings was abrasive wear.

Novel fluorine-functionalized Ti3C2Tx/TiO2 hybrid coatings with enhanced weatherability, antifouling, and interfacial anticorrosion performances

As a valuable symbol of human cultural heritage, bronze inevitably endures varying degrees of corrosion due to environmental change. Thus, developing an efficient protective coating for bronze is crucial to ensure bronze relics receive more protection. Herein, a multifunctional organic-inorganic hybrid composite coating of 1 H,1 H,2 H,2 H-Perfluorodecyltriethoxysilane (PFDTES), Ti3C2Tx nanosheets and TiO2 nanoparticles (PFDTES@Ti3C2Tx/TiO2) are successfully prepared and coated the bronze, which exhibits excellent anti-corrosion, weathering stability and superhydrophobicity. The superhydrophobicity of coating is derived from introducing a low surface energy C-F bond. Furthermore, the corrosion protection ability can be improved by the barrier effect of Ti3C2Tx nanosheets, and TiO2 nanoparticles can enhance the weathering stability of coatings by providing exceptional abrasion resistance and ultraviolet (UV) resistance capabilities. Morphological examination, X-ray photoelectron spectroscopy, an accelerated aging test, and electrochemical measurements, among other methods, were used to research the protective effect and anticorrosion performance of organic-inorganic hybrid coatings. It can be found that the composite coatings have a large water contact angle (153°) and form a superhydrophobic surface. Furthermore, electrochemical results show that the superhydrophobic PFDTES@Ti3C2Tx/TiO2 coating has a higher low-frequency impedance modulus and lower current density than the uncoated substrate, indicating enhanced corrosion resistance. Based on solid and liquid pollutant tests, the PFDTES@Ti3C2Tx/TiO2 coatings also showed good self-cleaning and antifouling properties. And coating maintained good transparency without changing the bronze color and appearance. In conclusion, the superhydrophobic PFDTES@Ti3C2Tx/TiO2 composite coating has potential applications in the field of bronze protection.

An environmentally friendly coating: Excellent self-cleaning, efficient antimicrobial, and durability properties

The development of non-polluting and non-toxic polymer antimicrobial agents is a prominent focus in contemporary research and development. Polymer quaternary ammonium salts are particularly promising for their antimicrobial efficacy. In this study, we synthesized quaternary imidazole derivatives using butylimidazole and 3-chloropropyltriethoxysilane. We then prepared PDMS/BIS/PPS hydrophobic antimicrobial composite coatings by incorporating quaternary ammonium salt chemically grafted silica (BIS), polyphenylene sulfide (PPS), and polydimethylsiloxane (PDMS). The resulting composite coating displayed a high contact angle of 136.4°±1° and a low sliding angle of less than 5°±1°, indicating its hydrophobic nature. Electrochemical assessments demonstrated exceptional corrosion resistance, with a corrosion inhibition rate of 99.967 %. Bacterial assays confirmed the coating's effectiveness in inhibiting bacterial proliferation, especially against E. coli. The quaternary ammonium-modified silica particles in the coating facilitate bacterial adsorption through electrostatic interactions, which compromise cell membrane permeability, obstruct nutrient uptake, and induce apoptosis. With its anti-fouling, self-cleaning, and anti-corrosion properties, this coating has substantial potential for applications in various fields, including medical devices, and food packaging.

Thermal Corrosion Properties of Composite Ceramic Coating Prepared by Multi-Arc Ion Plating

In this study, a NiCr/YSZ coating was applied to a γ-TiAl surface using multi-arc ion plating technology to enhance its high-temperature performance and explore the mechanisms of high-temperature oxidation and thermal corrosion. The thermal corrosion properties of the γ-TiAl matrix and NiCr/YSZ coating were investigated at 850 °C and 950 °C using a constant-temperature corrosion test in a 75% Na2SO4 + 25% NaCl mixture. The results indicate that after 100 h, the thermal corrosion weight gain of the coating samples was 70.1 mg/cm2 at 850 °C and 118.2 mg/cm2 at 950 °C. At these temperatures, sulfide formation on the surface increases, leading to a loose and porous surface. After 100 h of high-temperature corrosion at 850 °C, the primary oxidation product on the surface of the coating was tetragonal-ZrO2. At 950 °C, Y2O3, which mainly acts as a stabilizer in YSZ, reacted with Na2SO4, resulting in the continuous consumption of Y2O3. This reaction caused a substantial amount of tetragonal-ZrO2 to transform into monoclinic-ZrO2, altering the volume of the ceramic layer, which induced internal stress, crack propagation, and minor spallation. A continuous and dense internal thermally grown oxide (TGO) layer effectively impeded the diffusion of molten salt substances and oxygen, thereby significantly improving the thermal corrosion resistance of the thermal barrier coating.

Harnessing optimized SiO₂ particles for enhanced passive daytime radiative cooling in thin composite coatings

Passive daytime radiative cooling (PDRC) technologies can achieve sub-ambient temperatures by reflecting sunlight and radiating heat to outer space without energy consumption. Conventional PDRC structures, however, suffer from high costs, limited scalability, and poor resistance to pollution. This study presents an optimized Stöber method combined with cetyltrimethylammonium bromide (CTAB) modification to synthesize SiO₂ particles (SiP-C) with nano-synapses surface morphology (30–50 nm) and a broad particle size distribution (100–800 nm). These features facilitate both Rayleigh and Mie scattering, resulting in excellent solar reflectance (97 %) and selective emissivity (0.95). By mixing SiP-C with polyvinylidene fluoride (PVDF), a PDRC coating was fabricated using a simple blade-coating method. The coating, with a thickness of only 143 μm, demonstrated a solar reflectance of 95 % and emissivity of 0.98, achieving a cooling temperature of 10.5 °C below the shielded air temperature under high solar irradiance (981 W/m2) and relative humidity (56.4 %). The SiP-C nano-synapses also imparted hydrophobic properties (contact angle of 142°), enhancing resistance to environmental pollution. The composite PDRC coating thus offers scalability, low cost, high performance, and compatibility for various energy-saving cooling applications.

Laboratorial investigation on optical, thermal and pavement performance of biomimetic dark reflective coatings with composite structure for pavement cooling

The surface temperature of asphalt pavement in summer can reach up to 70 °C, which leads to poor outdoor thermal comfort and exacerbates the urban heat island effect. Reflective coatings can effectively reduce pavement temperature, but their intrinsic light color with high reflectance causes safety issues such as glaring. In this study, based on the biomimetic idea of chameleon skin structure, composite pavement coatings for cooling and anti-glare were developed. Their optical properties, thermal behavior, adhesion and skid-resistance performances were investigated. The results showed that near-infrared reflectance of black and grey double-layer reflective coatings could reach 0.66 and 0.70, respectively (58 % higher than single-layer coatings). The optimal mass fraction of perylene black in the upper black/grey coating was 2.94 % and 0.74 %, respectively. The double-layer dark coatings could decrease the temperature by 14 °C at the depth of 3 cm below road surface, which achieved cooling effect close to that of white single-layer reflective coatings. The adhesion between coating and stone was generally higher than the cohesion of asphalt, therefore, opening traffic for a period of time or carrying out micro-milling before coating could improve the abrasion resistance. Due to increase in the thickness of the double-layer coating, the microscopic texture of road surface was reduced, thereby reducing skid-resistance. However, it still met the standard requirements. This study intends to provide a reference for developing pavement coatings that balance cooling and visual safety to mitigate the heat island effect, and improve the sustainability of transportation infrastructure.

Assessment of the microstructure, adhesion and elevated temperature erosion resistance of plasma-sprayed NiCrAlY/cr3C2/h-bn composite coating

This study uses an air jet erosion tester to investigate the erosion behavior of NiCrAlY/Cr3C2/h-BN composite coatings that are plasma-sprayed at three different temperatures and 40 m/s on T22 boiler steel alloy. 30 and 90° are the impingement angles. To identify the erosion mechanism, SEM and X-ray diffraction techniques are used to analyze the surface morphology and phase generated on the eroded surface. Findings of erosion test indicate that the erosion resistance was notably enhanced by addition of Cr3C2 and h-BN because of its lubricating characteristics and capacity to reduce frictional forces during erosion. The combined influence of Cr3C2 and h-BN enhanced the coating hardness and erosion wear resistance, thereby improving its overall resistance to erosion. The weight loss method was employed to calculate the erosion rate, and the NiCrAlY/Cr3C2/h-BN coating showed up to 30.55% and 34.48% lower erosion rate as compared to uncoated T22 substrate at 600 °C for 30° and 90° impact angles, respectively. This characteristic is affected by the hard reinforcement Cr3C2's high-temperature stability, the h-BN's self-lubricating ability, the formation of a protective oxide layer that forms at 600 °C, and the eroded coating's ductile behavior of material removal. The study also reveals that the NiCrAlY/Cr3C2/h-BN coating system on T22 boiler steel alloy has excellent erosion resistance, making it suitable for use in high-temperature and erosive environments in boiler systems and similar industries.

Microstructure evolution and tribological properties over a wide temperature range of Ni-based composite coatings with Ti3AlC2 addition

Ni60A alloy powders doped with varying concentrations (0, 10 wt% and 20 wt%) of Ti3AlC2 MAX phase were coated on S31008 NiCr stainless steel substrate using atmosphere plasma spraying technique in this work. Comparative investigation was conducted to examine the effects of Ti3AlC2 additions on the microstructure evolution, microhardness, and wide temperature range (room temperature to 800 oC) tribological performance of the composite coatings. The findings demonstrated that the composite coatings were composed of γ-Ni, intermetallic hard metal borides, Ti3AlC2 and TiC phases, without any noticeable oxide phases. The 20 wt% Ti3AlC2 additions to the Ni60A alloy coating exhibited minimum imperfections in microstructure with a porosity drop of 65.8 %, and the highest microhardness which was enhanced by 64 % to 924 HV0.515. After introducing of Ti3AlC2, the coefficient of friction decreased and appeared to distinguish itself by remaining minimal and stable at low-medium temperatures compared with an increase of more than 70 % at high temperatures. Ni60A-10 wt% Ti3AlC2 coating resulted in the lowest friction coefficient of approximately 0.45 from room temperature to 400 oC and it peaked to 0.78 at 800 oC, reducing by 19.6 % and 6 % compared to non-composite coating, respectively. The wear resistance of the composite coating was considerably improved with the increment of Ti3AlC2, and the coating with 20 wt% Ti3AlC2 showed the most significant reduction in wear rate: 18.5 % at room temperature, 45.2 % at 200 oC, 37.2 % at 400 oC, 60 % at 600 oC, 90.8 % at 800 oC. The lubricate layered Ti3AlC2 phases and the tribo-oxide film predominate composed of derivative NiO, Cr2O3 Al2O3 and TiO2 played a critical role in antifriction and wear resistance. The wear mechanisms were accordingly conducted as abrasion and adhesion wear at low-medium temperature and transferred into tribo-oxidation wear at elevated temperature.

Effect of graphene content on the tribological and corrosion behavior of high-speed-laser-clad high-entropy-alloy composite coatings

To repair oil drill pipe joints that have failed owing to dry wear and tribocorrosion, graphene-reinforced CoCrFeMo0.5NiTi0.5 high-entropy alloy composite coatings (HEACCs) were developed through high-speed laser cladding. The HEACC containing 1.5 wt% graphene exhibited dry wear and tribocorrosion rates that were 59.18 % and 32.20 % of those observed in the high-entropy alloy coating, respectively. The HEACC exhibited a corrosion current density of 2.475 × 10−7 A/cm2. The HEACC containing 1.5 wt% graphene underwent progressive damage during dry wear owing to the combined effects of abrasive wear, which created furrows; adhesive wear, which led to flaking; and oxidative wear, which formed oxide layers. During tribocorrosion, chloride ions exacerbated surface damage caused by hard abrasives and asperities, intensifying corrosive–abrasive wear interactions.

INDUSTRIAL DESIGN OF HAZARDOUS PRODUCTION FACILITIES

The risk-oriented approach to industrial safety allows for the operation of hazardous production facilities in the cracks presence. There is a problem of assessing the critical size of cracks by non-destructive methods, which are currently not widely tested and standardized. Changing operating conditions and damage accumulation can transfer cracks into the category of developing cracks, and this can lead to catastrophic consequences. From this point of view, close proximity of objects containing explosive substances, as it is the case at processing plants, pumping stations, production platforms, poses a danger. Visualization of hazardous objects and their location areas warns the personnel about the need to comply with increased safety measures. This is aimed at using industrial design, which defines the principles of warning of hazardous objects by using color signs. A common trend in the coating usage is their multifunctionality. In this regard, the present research attempts to combine color warning signs with the possibility of their usage in composite coatings designed for corrosion protection, as well as showing the changes in temperature conditions of processes.