Composite Coatings Research Articles

Microstructure evolution, wear and corrosion behavior of WC reinforced CoCrFeNiMn high-entropy alloy composite coatings by induction cladding

In this study, CoCrFeNiMn high entropy alloy (HEA) composite coatings reinforced with different WC particle contents were prepared by induction cladding technology for the first time. The effects of WC particle contents (0–70 wt%) on the microstructure, hardness, wear resistance and corrosion resistance of the coatings were analyzed. The results showed that the coatings prepared by induction cladding exhibited good metallurgical bonding with the substrate. The addition of WC particles led to grain refinement in the CoCrFeNiMn HEA together with second-phase strengthening and solid solution strengthening, improving the microhardness of the coatings. Compared to the average hardness value of 183 HV0.5 for the CoCrFeNiMn HEA coating, the composite coating with 60 wt% WC particle content exhibited the highest average hardness value of 679 HV0.5. The addition of WC particles significantly enhanced the wear resistance of the composite coating, with wear mechanisms including adhesive wear, abrasive wear, fatigue wear and oxidation wear. The composite coating with 60 wt% WC particle content demonstrated outstanding wear resistance, with a specific wear rate value of 0.491 × 10−6 mm3N−1 m−1, representing a reduction of approximately 670 times compared to the CoCrFeNiMn HEA coating. However, the addition of WC particles caused uneven potential distribution within the composite coatings, leading to galvanic corrosion. The WC particles and precipitated carbides increased the defects in the passive film, thus reducing the corrosion resistance of the composite coatings.

Effect of W content on the wear resistance of Inconel 625/Y2O3 composite coatings by laser cladding

In this study, tungsten (W) reinforced Inconel 625/Y2O3 composite coatings were fabricated on Inconel 625 substrates by laser cladding, and the effect of the content of W on the phase composition, microstructure, microhardness and wear resistance of the coatings were investigated. The addition of W relieves the residual stresses in the clad layer and has less effect on the deformation of the substrate. In addition, W can promote the precipitation of Laves phase while refining the grains. Excessive W content promotes the generation of more Laves phases in the coating and leads to W precipitation. It increases the microhardness of the coating, but causes microstructure unevenness. Y2O3 is enriched at the grain boundaries in the form of particles, which plays a role of pinning and inhibits the diffusion of the grain boundaries. When the content of W reaches 6 wt%, the coating shows the best wear resistance with solid solution strengthening, fine grain strengthening and hard phase. When the content of W reaches 9 wt%, the uneven distribution of the microstructure of the coating weakens the strengthening effect.

Carbon Nanotube–Polymer Composite Coating on the Anode Surface for Enhancing the Performance of Zn-Ion Batteries

Carbon Nanotube–Polymer Composite Coating on the Anode Surface for Enhancing the Performance of Zn-Ion Batteries

Impact of ultraviolet aging on the composition and characteristics of multifunctional composite coatings

AbstractMultifunctional composite coatings exposed to environmental conditions are prone to aging and potential functional failure due to ultraviolet (UV) radiation. This study investigates the impact of UV radiation on the structure and properties of low infrared emissivity composite coatings, comprising ethylene propylene diene monomer (EPDM) as the matrix and antistatic carbon fiber (CF) and flaky floating aluminum powder as fillers. In addition to analyzing the photochemical degradation reactions of the composite coating under UV irradiation, the role of fillers in resisting UV aging is elucidated. The performance parameters examined include infrared (IR) emissivity, surface resistivity, mechanical properties, and dielectric properties. The results indicate that after UV aging, EPDM undergoes the most significant changes, leading to the formation of carbonyl groups. CFs experience mild UV aging and an increase in resistivity. Aluminum powder, on the other hand, remains largely unchanged after UV aging and its addition significantly reduces the UV aging rate of the composite coating, resulting in a low IR emissivity of as low as 0.2 after UV aging. Among them, Coating 4 exhibits the best overall performance after UV aging.Highlights The UV aging mechanism of EPDM and the role of fillers were revealed. The UV aging of the coating significantly reduced the infrared emissivity (Reduced from 0.5 to 0.2). Al powder effectively reduced the UV degradation rate of the coating by reflecting UV light. The properties of the double‐formulated coating perform best after UV aging.

Preparation and properties of Mg-Nd binary alloy MAO/SiO2@α-Fe2O3 organic composite coating

In order to make magnesium alloys better used in aviation, electronic information and other fields, it is necessary to improve their corrosion resistance and wave absorption properties. In this paper, a composite coating with corrosion resistance and wave absorption properties was prepared on magnesium alloy by micro-arc oxidation-organic coating technology. An organic absorbing coating with a thickness of about 40 μm was sprayed on the MAO coating containing Yb2O3 nanoparticles. Among them, the absorbing fillers in the organic coating are mainly SiO2 and α-Fe2O3. Three different mass ratios of SiO2 and α-Fe2O3 were set to 20%, 22.5% and 25%, respectively, to prepare three different MAO/SiO2@α-Fe2O3 organic composite coatings. The morphology, roughness, microstructure and chemical composition of the organic composite coating are characterized. The results show that after coating the organic composite coating, the roughness of the coating is significantly reduced, and the compactness and interlayer adhesion of the coating are significantly improved. The electrochemical test and SKPFM test of the organic composite coating were carried out. The results showed that with the increase of the mass ratio of SiO2 and α-Fe2O3, the corrosion resistance and stability of the organic composite coating increased, and the Volta potential also gradually moved up. The microwave absorbing properties of organic composite coatings were studied by vector network analyzer. The results show that the microwave absorbing properties of the coatings are positively correlated with the mass ratio of SiO2 and α-Fe2O3.

Mechanical properties and tribological behaviors of Ag/graphene composite coating under sliding friction and current-carrying fretting

Charging connector of electric vehicles faces two working conditions of sliding friction and current-carrying fretting. Traditional Ag coating is difficult to meet the performance requirements. Herein, Ag/graphene composite coatings were prepared by electroplating, and the chemical compositions, crystal phase, mechanical and tribological properties were studied. The results showed that adding graphene increased the hardness, elastic modulus and toughness. Under sliding friction and current-carrying fretting, Ag/graphene coating exhibited low COF and wear, stable and low ECR. The sliding friction mechanism was dominated by abrasive wear, while the current-carrying fretting mechanism was dominated by adhesive and fatigue wear. The worn surface analysis indicated that the superior tribological properties were attributed to the improved mechanical properties and the formation of transfer film.

Facile fabrication of linezolid/strontium coated hydroxyapatite/graphene oxide nanocomposite for osteoporotic bone defect

Hydroxyapatite (HAp) coatings currently have limited therapeutic applications because they lack anti-infection, osteoinductivity, and poor mechanical characteristics. On the titanium substrate, electrochemical deposition (ECD) was used to construct the strontium (Sr)-featuring hydroxyapatite (HAp)/graphene oxides (GO)/linezolid (LZ) nanomaterial coated with antibacterial and drug delivery properties. The newly fabricated nanomaterials were confirmed by X-ray diffraction analysis (XRD), Fourier-transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS) analysis and morphological features were examined by scanning electron microscope (SEM) analysis. The results reveal multiple nucleation sites for SrHAp/GO/LZ composite coatings due to oxygen-comprising moieties on the 2D surface of GO. It was shown to be favorable for osteoblast proliferation and differentiation. The elastic modulus and hardness of LZ nanocomposite with SrHAp/GO/LZ coatings were increased by 67 % and 121 %, respectively. An initial 5 h burst of LZ release from the SrHAp/GO/LZ coating was followed by 14 h of gradual release, owing to LZ's physical and chemical adsorption. The SrHAp/GO/LZ coating effectively inhibited both S. epidermidis and S. aureus, and the inhibition lasted for three days, as demonstrated by the inhibition zone and colony count assays. When MG-63 cells are coated with SrHAp/GO/LZ composite coating, their adhesion, proliferation, and differentiation greatly improve when coated with pure titanium. A novel surface engineering nanomaterial for treating and preventing osteoporotic bone defects, SrHAp/GO/LZ, was shown to have high mechanical characteristics, superior antibacterial abilities, and osteoinductivity.

TiO2 deposited dual functional hydrogel coatings with superhydrophilic and photocatalytic properties for efficient oil/water separation and dye photodegradation

Hydrogel coatings have been applied in oil/water separation owing to the underwater superoleophobic and anti-oil fouling property. However, the intrinsic relatively poor mechanical performance of hydrogel coatings and inevitably polluted by organic pollutants induce the separation performance reduction in the long-term operation and even possibly cause the coatings to peel off. In this work, we developed a simple and robust TiO2 deposited polyacrylamide-sodium alginate (TiO2@PAS) composite hydrogel coating with underwater superoleophobic and dye photodegradation abilities. PDA/TiO2 nanoparticles were deposited on the substrate surface through the mussel inspired chemistry strategy. Moreover, Polyacrylamide and calcium alginate were crosslinked into the double network hydrogel to enhance mechanical performance. The prepared hydrogel coating was introduced onto different substrates to endow the coated substrates with robust superwetting and anti-oil fouling properties. Separation efficiency of TiO2@PAS hydrogel coated copper mesh for oil/water mixtures reached 99.1% after 50 cycle separation tests. The hydrogel coated PVDF membrane was prepared through the same method and separation efficiency for oil-in-water emulsion keeps above 99.3% during multiple cycles separation. Moreover, the photocatalysis active TiO2 nanoparticles allowed the TiO2@PAS composite hydrogel coating to degrade the organic dye methylene blue (MB) through the photo-Fenton-like photodegradation process with degradation efficiency as high as 98.7%. Notedly, the TiO2@PAS hydrogel coating shows robust superwetting performance even underwent abrasion test and acid-base immersing, which has the potential for adapting extreme operating condition. Overall, the study on the TiO2@PAS composite hydrogel coatings provides a general and simple design strategy for superwetting and photocatalytic hydrogel coatings for multi-demand water treatment application.

Enhancing weatherability and mechanical properties of tung oil wood finishes through natural rubber modification via the Diels-Alder reaction

Tung oil is commonly utilized for coating protection in wooden products, often attracting attention for its appearance, antimicrobial capabilities, and insect-resistant coatings. However, its poor mechanical properties and poor weather resistance stem from excessive self-crosslinking of surplus conjugated double bonds and molecular chains, resulting in poor film wrinkling. Therefore, this study introduces natural rubber via the Diels-Alder reaction to consume the residual double bonds in tung oil, resulting in tung oil/natural rubber composite coatings (NRTO) with excellent mechanical properties and weather resistance. The results indicate that NRTO exhibits excellent mechanical properties, including high elongation (32 %) and strong adhesion (4.55 MPa). Furthermore, NRTO demonstrates outstanding acid resistance and UV aging resistance. Given its many benefits, NRTO film emerges as a promising candidate for substantially protecting wood surfaces in demanding environments.

Synergistic effect of Al2O3 and MoS2 on the corrosion behaviour of plasma sprayed aluminium matrix composite coating

In this study, the incorporation of alumina (Al2O3) and molybdenum disulfide (MoS2) in Aluminium (Al) was successfully fabricated through shroud plasma spray. This strategic incorporation of MoS2 and Al2O3 effectively fills voids, leading to a remarkable reduction in inherent porosity within the aluminium coating, achieving an impressive ∼76.54 % reduction. These composite coatings exhibited outstanding hydrophobicity (contact angle ∼119°), signifying remarkable water repellency and anti-corrosion properties compared to bare aluminium (contact angle ∼81.7°). During the electrochemical corrosion test, the corrosion rates (CR) of Al coating (CR = 9.14 mpy) was notably around 23 times higher compared to MoS2 and Al2O3 reinforced aluminium composite coating (CR = 0.372 mpy) in a 3.5 wt % NaCl electrolyte. The subsequent post-corrosion analysis further confirmed the composite coating's efficiency in mitigating the impact of corrosive salts, underlining the effectiveness of the hybrid coating in combating corrosion attacks. A corrosion behaviour prediction model was established based on computational and experimental data.

Application of Carboxymethyl Cellulose and Its Edible Composite Coating in Fruit Preservation

ABSTRACTFruits are highly susceptible to quality deterioration and spoilage during postharvest storage. Edible coating emerges as an effective strategy to prolong the postharvest life of fruit and enhance their quality during storage. Carboxymethyl cellulose (CMC) is a polysaccharide derivative widely applied in various industries due to its excellent barrier and mechanical properties. CMC has been utilized as an edible coating material for postharvest preservation of fruit for many years. Ongoing research is centred on the development of composite films by integrating CMC with natural biopolymers or potential active agents to augment their functionality in postharvest fruit preservation. This review consolidates findings on composite coatings of CMC combined with various materials for fruit storage and preservation, shedding light on the challenges associated with such composite coatings.

Fabrication of a Universal Composite Coating for Biliary Stents with Protein Antifouling and Antibacterial Synergies

Fabrication of a Universal Composite Coating for Biliary Stents with Protein Antifouling and Antibacterial Synergies

Recent Advances in Corrosion Inhibition of Bonded NdFeB Magnets.

Bonded permanent NdFeB magnets are useful in numerous applications, including electric vehicles, and the demand is steadily increasing. A major drawback is corrosion due to inadequate wetting of the magnetic particles by liquid polymers such as polyphenylene sulfide or polyamide. Recently reported methods for corrosion inhibition are summarized, and their applicability is critically evaluated. The phosphorylation of magnetic particles inhibits corrosion but does not enable appropriate properties in harsh environments. The same applies to metallic coatings, which usually contain aluminum and zinc. Advanced epoxy adhesives are a promising solution, although some authors have reported inadequate corrosion resistance. The application of composite coatings seems like an appropriate solution, but the exact mechanisms are yet to be studied.

Effects of Al2O3 content on the microstructure and performance of Inconel 625-xAl2O3 composite non-skid coatings by plasma enhanced high-velocity arc spraying

The efficient preparation of metal/ceramic composite coatings with excellent performance has been a hot research topic in the field of thermal spraying. In this study, a novel plasma enhanced high-velocity arc spraying (PE-HAS) technique is developed. A series of Inconel 625-xAl2O3 composite non-skid coatings are deposited by PE-HAS with different feeding ratio of alloy wire (1.6 mm in diameter) and ceramic powder (13.5 μm in average particle size). Specifically, the microstructure, mechanical properties, corrosion resistance and tribological performances of the coatings have been comprehensively investigated. Results indicate that all of the composite coatings with different Al2O3 contents are characterized by high densities, low defects (porosity≤3.52 %), strong bonding (≥50 MPa) and high friction coefficient (≤ 1.034). The coatings with low Al2O3 content feature a more homogeneous structure and superior bonding strength. The microhardness and wear resistance of the coatings increases significantly with increasing Al2O3 content, which should be attributed to the formation of many localised enhancement areas composed of different forms of Al2O3 phases. It is worth noting that the unique feedstock feeding method promotes the formation of the in-situ double-layer structure of coatings with high Al2O3 content, which further improves the wear and corrosion resistance. However, the friction coefficient gradually decreases when the Al2O3 content is too high, thus affecting the anti-slip performance of the coating.

Effects of ZrW2O8 Content on the Microstructures and Properties of Composite Coatings Produced by Laser Cladding

Addressing the issue of cracking in laser-cladding Ni-based composite coatings with WC particles, this study explored an approach to fabricating a crack-free coating by incorporating ZrW2O8 powder. The influence of varying ZrW2O8 contents on the crack susceptibility, microstructure, microhardness, wear resistance, and corrosion resistance of Ni60/WC composite coatings was systematically examined. The findings indicate that the ZrW2O8 content significantly impacts the microstructure and functional properties of the coating. Furthermore, it is suggested that the main contributors to preventing crack formation and diffusion are believed to be the pressure interaction caused by the negative expansion effect of ZrW2O8, as well as the in situ phase transition and diffusion toughening of ZrO2 during its decomposition process. The feasibility of achieving crack selfhealing through the addition of specific amounts of ZrW2O8 powder has been conclusively demonstrated.

The Durability of Simvastatin Nanoparticle Coatings on Dental Implant Healing-Abutments

Background: Considering the success of dental implant treatments and their long-term effectiveness, it is important to prevent a series of biological complications such as peri-implant diseases. The development of antimicrobial coatings is known as a promising strategy to overcome these challenges. This study aimed to investigate the durability of simvastatin-loaded gelatin nanoparticle coating on titanium healing abutments. Methods: 40 titanium healing abutments were prepared in two groups, including the test group (titanium healing abutments coated with simvastatin nanoparticles, n=20) and the control group (titanium healing abutments without simvastatin nanoparticle coating, n=20). The dip-coating process was then applied to cover the surface of the healing-abutments. The morphology and composition of coatings were evaluated by Scanning Electron Microscope (SEM) and X-Ray Diffraction analysis (XRD), respectively. Results: The resulting data from SEM and XRD confirmed the successful coating of simvastatin- loaded gelatin nanoparticles on the implant. Based on the Sidak test results, it was observed that the average weight before coating and immediately after coating had a significant difference. Also, the average weight between the initial time (after coating) and the time of 1 day after coating and 30 days after coating was not statistically significant. It means that the coating has been stable for at least 30 days. The difference between the initial weight (after coating) and 60 days after plating was significant. This means that the durability of the coating has decreased until the 60th day. Conclusion: The resulting data showed that the coating of gelatinous nanoparticles containing simvastatin on the titanium healing abutments was successful, and the durability of the coating lasted for at least 1 month.

Tribological properties and solid particle erosion wear behavior of Al2O3-13 wt%TiO2/Al2O3-PF composite coatings prepared on resin matrix by supersonic plasma spraying

Resin materials feature exceptional physical properties and inexpensive cost, but unfavorable surface characteristics, such as low wear resistance and poor erosion wear performance, render them tough to satisfy greater demands. The potential option is to prepare supersonic plasma sprayed Al2O3-13 wt%TiO2/Al2O3-phenolic resin (AT13/Al2O3-PF) coating on the surface of the resin matrix. AT13 feedstocks are classified into two types: Al2O3-13 wt%TiO2 powder prepared by the agglomeration granulation process (AT13-1) and the mixture of spherical Al2O3 and TiO2 (approximately 13 wt%) powder (AT13-2). The effect of component dispersion on mechanical and tribological characteristics of coatings was thoroughly investigated, as well as the solid particle erosion wear behavior of coatings. The results illustrated that the evenly dispersed TiO2 phase in AT13-1 coating was prone to homogenize the coating structure, resulting in better tribological characteristics than AT13-2 coating, although erosion wear performance was inferior to AT13-2 coating. The wear rate of AT13-1 coating was 1.36 × 10−5 mm3 (N m)−1, which was 1/21 times that of AT13-2 coating. At the 60° erosion angle, the high porosity of AT13-1 coating resulted in hard phase cracking or hard phase debonding. The high microhardness of AT13-2 coating reduced erosion wear at the 90° erosion angle.

Effect of MoS2 nanoparticles on the properties of Ni-W-SiC composite coatings

To improve the comprehensive protection performances of Ni-W-SiC composite coatings, we successfully manufactured Ni-W-SiC-MoS2 composite coatings using an electrodeposition technique on a 7075 aluminum alloy surface. We analysed the changes in microhardness, wear resistance, corrosion resistance, surface morphology and roughness of the composite coatings upon the addition of MoS2 nanoparticles. A microscopic characterisation of the Ni-W-SiC-MoS2 coatings was carried out by scanning electron microscope and atomic force microscope. The elemental composition was analysed by energy dispersive spectroscopy. The grain size was calculated by X-ray diffraction. The microhardnesses of the Ni-W-SiC-MoS2 composite coatings were evaluated by a microhardness tester, the wear resistance was tested by a rotary friction tester, and the corrosion resistance was evaluated using an electrochemical workstation. The tests indicate that the addition of MoS2 nanoparticles has significant effects on the micromorphology and grain size of Ni-W-SiC,and that they can uniformly codeposit with SiC nanoparticles in the Ni-W coating, exerting a synergistic effect on the improvement in the performance of the composite coating. When the amount of added MoS2 is 8 g/L, the Ni-W-SiC-MoS2 coating has the smallest grain size and highest microhardness (917.6 HV). Its corrosion resistance is considerably improved compared to that of the Ni-W-SiC coating. When the MoS2 concentration is 6 g/L, the Ni-W-SiC-MoS2 coating has the highest content of MoS2 nanoparticles, the friction coefficient reaches the minimum (0.24), and the wear resistance is best.

Surface modification of titanium implants via PLLA/HA fibrous composite coating to improve piezoelectric properties

Titanium (Ti)-based implants are among the most advantageous biomaterials in both orthopedic and dental applications, owing to their excellent properties and biocompatibility. However, their bioinert surface poses challenges to osteointegrity, raising concerns about implant loosening. The present study examines the effect of surface modification of Ti by applying a bioactive piezoelectric fibrous coating comprised of electrospun poly(L-lactide) (PLLA) as a biodegradable piezopolymer and varying amounts of hydroxyapatite (HA) filler (5−20 wt%) as an osteoconductive piezoceramic. According to SEM micrographs, adding HA increased the fiber diameter, porosity, and pore size of the fibrous structure. Furthermore, peeling test of the fibrous coating demonstrated that applying a polydopamine (PDA) coating before electrospinning onto the Ti substrate effectively enhanced the adhesion strength of the coating. Additionally, the PLLA/HA composite coating exhibited increased piezoelectric properties, with piezoresponse rising from 2.41 ± 0.192 mV/N (5 wt% HA) to 5.42 ± 0.192 mV/N (20 wt% HA). Similarly, PLLA/HA coatings showed superior apatite-forming ability in simulated body fluid (SBF) at 7 and 28 days, with significantly higher calcium-phosphate deposition and a Ca/P ratio close to natural bone, surpassing the neat PLLA coating and bare Ti substrate. Finally, testing with MG-63 cell lines indicated that fibrous composite coatings enhance cell support, demonstrating optimal alkaline phosphatase (ALP) secretion levels and positive cell attachment. Consequently, the surface-modified Ti with fibrous PLLA/HA coating emerges as a promising strategy for the clinical treatment of bone defects.

Tuning biomechanical behavior and biocompatibility of Mg–Zn–Ca alloys by Mn3O4 incorporated plasma electrolytic oxidation coatings

In this study, the mechanical behavior and biocompatibility of plasma electrolytic oxidation (PEO)-coated Mg–Zn–Ca alloy specimens were investigated. The coatings were synthesized by incorporating KMnO4 and Mn3O4 nanoparticles into an electrolytic solution. An indentation test revealed a significant increase in the reduced elastic modulus of the PEO coatings with incorporated Mn3O4 under various loads. This increase was attributed to the higher coating thickness and reduced porosity achieved by the addition of Mn-based additives to the electrolyte. The composite PEO coatings prepared with Mn3O4 nanoparticles exhibited a more pronounced reduction in elastic modulus under pressure. Wettability tests showed that the prepared coatings maintained their hydrophilic nature with water contact angles in the range of 25–63°. The presence of Mn3O4 in the PEO coatings provided a conducive environment for cell viability. The enhanced biocompatibility of the composite coatings achieved by incorporating KMnO4 into the electrolyte was particularly noteworthy. This improvement was attributed to the controlled release of Mn ions, which generates a microenvironment that favors cellular activities. The study showed that incorporating Mn3O4 into PEO coatings enhances mechanical properties, preserves hydrophilicity, and improves biocompatibility, thus indicating its potential for orthopedic implant applications.