Composite Surface Coatings Research Articles

Hydrothermal preparation of magnesium alloy surface composite coatings and its performance research

Magnesium alloys have great potential for industrial and aerospace applications due to their low density and high strength. Aiming at its defects of poor corrosion resistance and susceptibility to galvanic coupling corrosion in metal coatings, a composite coating was prepared on the surface of AZ91D magnesium alloy by the hydrothermal method. Scanning electron microscope, x-ray diffraction, and x-ray photoelectron spectroscopy were used to characterize the surface micromorphology, phase composition, and elemental valence and evaluate the adhesion of the coating to the substrate by the ASTM D3359-09 test standard. Electrochemical experiments were done in a 3.5% NaCl solution. The results show that there are nanoscale dense granular structures on the surface of the samples, and the main components of the coatings are Mg(OH)2, Al2O3, and MgSiO3. ASTM grade 4B is between coating and substrate. The corrosion rate of the best sample was reduced by a factor of 238.96 compared to the substrate, and the corrosion current density was reduced by two orders of magnitude. The corrosion rate and corrosion current of the samples after repeated friction did not change much compared with those before friction, which proved that the composite coating had better corrosion resistance and friction stability.

Morphological and functional characterization of electroplated Ni-graphene composite coatings

Composite coatings (CECs) are providing a unique technological advantage for improving mechanical and tribological surface properties. Among different methods, electrodeposition is one of the most exploited to produce composite surface coatings on metal substrates. However, the process parameters affect graphene distribution, coating morphology and performance. This paper investigates how different deposition conditions influence the inclusion of large Graphene nanoplates (GnPs) in a Nickel matrix and the coating morphology and tribological performance. Set the process condition such as electrical parameters and the galvanic bath, the work focuses on the stirring rate effect. To this end, Ni-GnP coatings were obtained by a laboratory setup and evaluated through surface profilometry, SEM characterization and a dry-sliding linear reciprocating wear test. The results highlight the influence of stirring on coating uniformity. The low stirring rate allows larger particles to be embedded, which are not thoroughly covered; however, they act as a solid lubricant and reduce the friction coefficient.

Influence of Dilution on the Mechanical Properties and Microstructure of Polyurethane-Cement Based Composite Surface Coating.

Polyurethane-cement composite are widely used in modern civil engineering, and the method of adding diluent is often used to adjust the construction process to adapt to the engineering environment. Studies have shown that the addition of diluent impacts the performance of polyurethane-cement based composite surface coatings, but there have been few reports on the influence of diluent content on the mechanical properties and microstructure of the coatings. To address this, polyurethane coatings with different diluent contents were prepared, and positron annihilation lifetime spectroscopy was used to test the microstructure of the coatings. The tensile strength and elongation at rupture were tested using a universal material testing machine, and the fracture interface morphology of each coating was observed by scanning electron microscopy. Finally, the correlation between the microstructure parameters and the mechanical properties of the coating was analyzed using grey relation theory. The results demonstrated that with the increase in diluent content, (i) the average radius of the free volume hole (R) and the free volume fraction (FV) of the coating both showed a trend of first decreasing and then increasing. The value of R was between 3.04 and 3.24 Å, and the value of FV was between 2.08 and 2.84%. (ii) The tensile strength of the coating increased first and then decreased, while the elongation at rupture decreased first and then increased. Among them, the value of tensile strength was between 3.23 and 4.02 MPa, and the value of elongation at fracture was between 49.34 and 63.04%. In addition, the free volume in polymers plays a crucial role in facilitating the migration of molecular chain segments and is closely related to the macroscopic mechanical properties of polymers. A correlation analysis showed that the R value of the coating had the greatest influence on its tensile strength, while FV showed a higher correlation with the elongation at rupture.

Influences of the cladding method and overlapping rate on the multi-channel overlapping of composite coatings

Composite surface coatings had poor flatness rates and unmelted gaps in the multi-channel overlapping process. The mathematical prediction models of the overlapping rate, flatness rate, and defect rate were established based on the single factor test to reveal the coupling effect of the overlapping rate on the flatness and defect rates (pore area and unmelted gaps) of coatings under different cladding methods. The large flatness rate and small defect rate were optimized to obtain the optimal overlapping rate under different cladding methods based on grey correlation analysis. Finally, the cladding efficiency was used as an index to determine the optimal cladding method. The model had a certain prediction ability. The flatness rate first increased and then decreased with the increased overlapping rate; the defect rate first decreased and then increases with the increased overlapping rate. The optimal overlapping rate was obtained with 30 % circular sequence overlapping to derive maximum surface flatness and the minimum defect rate. The coating could reach 13.986 mm2, and the cladding efficiency could reach 69.930 mm3/s at this time. Results showed that the multi-index grey correlation analysis had certain feasibility for the optimization of laser cladding process parameters. The work provides references for the multi-objective optimization of the surface properties of laser cladding composites as well as a theoretical basis for the comprehensive comparison of coating performance under different cladding methods and overlapping rates.

The Electrochemical and Microstructure Effects of TiB2 and SiC Addition to AA5052/Al2O3 Surface Composite Coatings in 0.5 M H2SO4 Solution

In this work, Al2O3, SiC, and TiB2 ceramic coatings with different formulations were produced on the surface of AA5052 matrix by gas tungsten arc welding (GTAW). The corrosion behavior of the composites and the base metal (BM) was evaluated in a solution of 0.5 M H2SO4 with electrochemical techniques such as open circuit potential (OCP) monitoring, potentiodynamic polarization (PDP), and electrochemical impedance spectroscopy (EIS). The morphology of the cladded surfaces was monitored by scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDS). Based on the PDP and EIS results, BM had the lowest corrosion rate in the 0.5 M H2SO4 solution. All composite coatings shifted to higher corrosion rate values than that of BM, indicating that AA5052 composites had lower corrosion resistance compared to the BM. SEM images of the corroded surface of BM exhibit minimum pitting corrosion in sulfuric acid media. According to electrochemical studies, AA5052/Al2O3 + SiC + TiB2 composite had the lowest corrosion resistance due to the formation of micro-galvanic sites on the aluminum matrix surface. However, the AA5052/Al2O3 + TiB2 composite showed the best corrosion performance compared to other composites. In general, by adding SiC and TiB2 ceramics to Al2O3 and fabricating binary composites, the corrosion resistance of AA5052/Al2O3 composite is improved. Although the corrosion resistance of AA5052 composites is lower than the BM, their higher surface hardness makes their use justified in applications where high mechanical properties are required if the environment is not too aggressive.Graphical Abstract

Investigating the influence of single-pass and double-pass friction stir processing on mechanical and wear behaviour of AA5083/Al2O3 surface

Friction Stir Processing (FSP) has established itself as an efficient technique to manufacture surface composite. Since the development of FSP, a variety of surface composite coatings have been produced with the help of this technique. Surface composite provides an enhancement in the material’s properties by providing a coating layer of composite material on the parent material. Various FSP process parameters can affect the produced surface composite and its properties. One of the important FSP parameters includes the number of passes over the surface of a material. In this paper surface composite of AA5083/Al2O3 was produced using FSP. Single-pass and double pass FSP were employed to understand its effect on microhardness, tensile strength, microstructure coefficient of friction, and wear rate. It was observed that the double pass aided to produce the homogeneously dispersed reinforcement particles in the surface composite along with fine grain microstructure. FSP helped to enhance the microhardness from 79.5 HV in the parent material to 136.5 HV in double pass FSP. Moreover, FSP helped to increase the tribological properties after two passes. However, the ultimate tensile strength was reduced after FSP.

Superhydrophobic silane-based surface coatings on metal surface with nanoparticles hybridization to enhance anticorrosion efficiency, wearing resistance and antimicrobial ability

Abstract A multifunctional silane-based composite surface coating with self-cleaning, anticorrosive and antimicrobial abilities have been fabricated on metal surface. The surface coating is designed to have a “sandwich” structure that contains a chemically etched surface at the bottom, a SiO2-hybridized silane layer in the middle and a Ti3C2-hybridized silane layer on the top. The chemical etching produces a rough surface that helps to produce superhydrophobicity. The silane molecules are crosslinked to form a film of low surface energy, which not only contributes to surface superhydrophobicity but also plays dominant roles in corrosion resistance. The SiO2 nanoparticles and Mxene (Ti3C2) nanosheets are hybridized in the film to enhance compactness, mechanical strength and wearing resistance of the film, resulting in a surface coating with excellent anticorrosion efficiency. Mxene can also introduce antimicrobial ability to the surface coating. The study develops an effective strategy to construct multifunctional composite surface coatings, which is not only suitable for modification of clinical and biomedical devices for anticorrosive and antibacterial purposes, but also can be used to modify the surface of daily-use facilities to facilitate their daily maintenance and cleaning.

Reserach of the mechanic-tribological characteristics of Ti3SiC2/TiC coatings after annealing

This article investigates the influence of thermal annealing on microhardness and wear resistance of the surface of steel U9/Y9 protected by a composite coating Ti 3 SiC 2 /TiC obtained by detonation sputtering. Thermal annealing was performed in the range of temperatures 700-900 ◦ C during 1 hour. Following annealing the formation of TiO 2 and an increase in the phase content of Ti 3 SiC 2 are observed. Higher microhardness was obtained in coatings subjected to annealing at 800 ◦ C, which can be explained by an increase in the content of carbonized titanium. As the annealing temperature rises further, the thickness of the oxide layer increases, leading to a decrease in the microhardness for the coatings annealed at 900 ◦ C. According to the results of tribological tests, formation of the oxide increases wear resistance of Ti 3 SiC 2 /TiC composite surface coatings.

Investigation on the Wear Properties of Ti/TiC/TiN Composite Coatings Prepared by Powder Cored Wires Through TIG Method at Nitrogen Atmosphere on Titanium Substrate

In this present study, Tungsten Inert Gas (TIG) welding and powder filled cored wires with nitrogen shielding gas were utilized to produce TiC and TiN surface composite coatings on the titanium (Ti) sheet substrate. The TIG procedure was done at same welding parameters for all of prepared samples. Phase analysis and microstructures were done by X-ray Diffraction (XRD), Energy-Dispersive X-ray Spectroscopy (EDS), Optical Microscopy (OM) and Scanning Electron Microscopy (SEM). The obtained results from XRD and EDS demonstrated that the presence of crystalline phases of TiC, TiN and Ti. SEM and OM exhibited formation of the spherical and dendritic TiC particles in a martensitic matrix and also, TiN pinhole areas with rough and collapsed arms. Maximum microhardness value obtained was 571 HV in the case of sample treated with TiC cored wire at 95%argon+5% nitrogen atmosphere. The Pin-on-disk wear tests showed that the coating with maximum hardness had a higher wear resistance due to the presence of fine and hard TiC particles in the high-impact toughness titanium alloy with uniform distribution.

Newly Developed Nickel-Boron Composite Surface Coatings with Pd Particles: Structural, Mechanical and Corrosion Properties

Ni-B and Ni-B-Pd composite coatings have been electrodeposited from an aqueous electrolyte using direct current. The Ni-B composite coating has been observed to be dense, smooth, and shows a globular, cluster of grains type morphology. On the other hand, the Ni-B-Pd composite coating is observed to be porous, highly rough and shows stacked crystal type morphology. The addition of palladium has significantly improved the crystallite size of the coating. From DSC analysis, it is observed that the Ni-B-Pd composite coating is thermodynamically more stable than the Ni-B composite coating. In spite of larger grain size and higher roughness the Ni-B-Pd coating is observed to exhibit higher hardness (≈40% higher) and elastic modulus (≈70% higher) than that of the Ni-B composite coating. Also, it has been observed to possess better protective property (almost three times) than that of the Ni-B composite coating.

Synergistic thermal stabilization of ceramic/co-polyimide coated polypropylene separators for lithium-ion batteries

To improve the safety of lithium-ion batteries (LIBs), co-polyimide (PI) P84 was introduced as a polymeric binder for Al2O3/polymer composite surface coatings on polypropylene (PP) separators. By monitoring the dimensional shrinkage of the PP separators at high temperatures, we verified a synergistic thermal stabilization effect between the Al2O3 ceramic and the PI polymeric binder. Although PI was thermally stable up to 300 °C, a coating consisting solely of PI did not impede the PP separator dimensional changes (−22% at 150 °C). On the other hand, the Al2O3/PI-coated PP separators efficiently impeded the thermal shrinkage (−10% at 150 °C). In contrast, an Al2O3/poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP) combination lowered the thermal stability of the PP separators (−33% at 150 °C). As a result, the Al2O3/PI-coated PP separators remarkably suppressed the internal short-circuit of the unit half-cells associated with separator thermal shrinkage (100 min at 160 °C), whereas the PVdF-HFP retained only 40 min under identical conditions. The Al2O3/PI-coated PP separators achieved rate capabilities and cell performances similar to those of the bare PP separators.

Nanoparticulate zinc oxide as a coating material for orthopedic and dental implants.

Orthopedic and dental implants are prone to infection. In this study, we describe a novel system using zinc oxide nanoparticles (nZnO) as a coating material to inhibit bacterial adhesion and promote osteoblast growth. Electrohydrodynamic atomisation (EHDA) was employed to deposit mixtures of nZnO and nanohydroxyapatite (nHA) onto the surface of glass substrates. Nano-coated substrates were exposed to Staphylococcus aureus suspended in buffered saline or bovine serum to determine antimicrobial activity. Our results indicate that 100% nZnO and 75% nZnO/25% nHA composite-coated substrates have significant antimicrobial activity. Furthermore, osteoblast function was explored by exposing cells to nZnO. UMR-106 cells exposed to nZnO supernatants showed minimal toxicity. Similarly, MG-63 cells cultured on nZnO substrates did not show release of TNF-α and IL-6 cytokines. These results were reinforced by both proliferation and differentiation studies which revealed that a substrate coated with exclusively nZnO is more efficient than composite surface coatings. Finally, electron and light microscopy, together with immunofluorescence staining, revealed that all cell types tested, including human mesenchymal cell (hMSC), were able to maintain normal cell morphology when adhered onto the surface of the nano-coated substrates. Collectively, these findings indicate that nZnO can, on its own, provide an optimal coating for future bone implants that are both antimicrobial and biocompatible.

Cold spray deposition characteristics of mechanically alloyed Cu-CNT composite powders

• Cu-CNT composite coatings were fabricated by mechanical alloying and cold spraying. • Cu-CNT composite coatings with up to 15 vol.% CNT were fabricated. • Cold spray deposition efficiency of powders decreased as CNT content increased. • Surfaces of the composite coatings contained about 1.0–2.5 vol.% micropores. • Uniform dispersion of CNT within the composite coatings was observed. Copper (Cu)-carbon nanotube (CNT) composite surface coatings with CNT contents of up to 15 vol.% were fabricated by mechanical alloying (MA) and cold gas dynamic spray (CGDS) process. The MA powder and CGDS coating samples were characterized by weight and size measurements, optical microscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray diffraction. The coatings were also examined by profilometry and porosimetry. The results showed that the particle sizes of MA composite powders and their deposition efficiencies (DEs) in CGDS decreased with the increase of CNT content. The DE also decreased with the increase of coating layers. The XRD results indicated that the composite powders and coatings had microstrains and undergone grain size reduction due to the deformation caused by MA and CGDS. The coating surface and internal microstructures had flattened lamellar features, which indicated severe deformation that resulted from impact during the deposition of particles as well as from the impact of the rebounded particles. Some internal pores were present along the interfaces of the deposited particles. The surface roughness values of the coatings were observed to be related to the sizes of the powder particles. The roughness tended to decrease with the reduction of particle sizes. Also, the coatings contained about 1.0–2.5 vol.% surface micropores. However, the comparison between the trend of the surface roughness and the quantity of surface pores did not show direct correlation. Composition analysis of the coatings revealed the uniform dispersion of CNTs within the coatings.

Wear Properties of (Ti,V)C/Fe Composite

(Ti,V)C particles reinforced Fe-based surface composite coatings were fabricated by in-situ synthesis and powder metallurgy route. The microstructure and wear properties were investigated by scanning electron microscopy and dry sliding wear test. The results show that fine (Ti,V)C particulates distribute uniformly in pearlite matrix; when V/Ti atomic ratio is 0.4, the wear weight loss of the composites achieve minimum.

Nucleate boiling heat transfer of R134a on cold sprayed CNT–Cu composite coatings

In this study, the application of mechanical alloying and cold spray process on the fabrication of carbon nanotube–copper (CNT–Cu) composite surface coatings for boiling heat transfer was investigated. Three types of coatings (5, 10, and 15 vol.% CNT) were fabricated. Boiling heat transfer of CNT–Cu composite coatings was investigated under a pool of saturated R134a at 4.8 ± 0.04 °C. Results showed that nucleate boiling can be enhanced by CNT–Cu composite powder coatings fabricated by cold spray. Incipience superheat of the coatings (5–6 K) was considerably lower than that of the plain Cu plate (8 K). At heat fluxes >20 kW/m2, significant differences in the enhancement ratios were observed. The maximum heat transfer coefficient enhancement achieved by the coatings was 1.21–1.74 times that of the plain Cu plate. The one-layer coating with 15 vol.% CNT exhibited the best boiling heat transfer performance in terms of lowering the superheat and enhancing the heat transfer coefficient.

Microstructural studies and wear assessments of Ti/TiC surface composite coatings on commercial pure Ti produced by titanium cored wires and TIG process

Tungsten Inert Gas (TIG) process and titanium cored wires filled with micro size TiC particles were employed to produce surface composite coatings on commercial pure Ti substrate for wear resistance improvement. Wire drawing process was utilized to produce several cored wires from titanium strips and titanium carbide powders. Subsequently, these cored wires were melted and coated on commercial pure Ti using TIG process. This procedure was repeated at different current intensities and welding travel speeds. Composite coating tracks were found to be affected by TIG heat input. The microstructural studies using optical and scanning electron microscopy supported by X-ray diffraction showed that the surface composite coatings consisted of α′-Ti, spherical and dendritic TiC particles. Also, greater volume fractions of TiC particles in the coatings were found at lower heat input. A maximum microhardness value of about 1100 HV was measured which is more than 7 times higher than the substrate material. Pin-on-disk wear tests exhibited a better performance of the surface composite coatings than the untreated material which was attributed to the presence of TiC particles in the microstructure.

Study on Microstructure and Wear Properties of (Ti,W)C/Fe Surface Composite Coating

(Ti,W)C particles reinforced Fe-based surface composite coatings were fabricated by in-situ synthesis and powder metallurgy route. The microstructure, interface and wear properties were investigated by X-ray diffraction, scanning electron microscopy and dry sliding wear test. The results show that (Ti,W)C carbides form via in situ reaction between titanium, ferrotungsten and graphite. The morphology of (Ti,W)C is mainly rectangular form. The interface between (Ti,W)C and iron matrix is found to be free from cracks and deleterious phases. The coating reinforced by (Ti,W)C particles possesses higher wear resistance than that of the substrate.

The influence of toothbrushing and coffee staining on different composite surface coatings

The aim of our study is to evaluate the performance of surface sealants and conventional polishing after ageing procedures. Eighty circular composite restorations were performed on extracted human molars. After standardised roughening, the restorations were either sealed with one of three surface sealants (Lasting Touch (LT), BisCover LV (BC), G-Coat Plus (GP) or a dentin adhesive Heliobond (HB)) or were manually polished with silicon polishers (MP) (n = 16). The average roughness (Ra) and colourimetric parameters (CP) (L*a*b*) were evaluated. The specimens underwent an artificial ageing process by thermocycling, staining (coffee) and abrasive (toothbrushing) procedures. After each ageing step, Ra and CP measurements were repeated. A qualitative surface analysis was performed with SEM. The differences between the test groups regarding Ra and CP values were analysed with nonparametric ANOVA analysis (α = 0.05). The lowest Ra values were achieved with HB. BC and GP resulted in Ra values below 0.2μm (clinically relevant threshold), whereas LT and MP sometimes led to higher Ra values. LT showed a significantly higher discolouration after the first coffee staining, but this was normalised to the other groups after toothbrushing. The differences between the measurements and test groups for Ra and CP were statistically significant. However, the final colour difference showed no statistical difference among the five groups. SEM evaluation showed clear alterations after ageing in all coating groups. Surface sealants and dentin adhesives have the potential to reduce surface roughness but tend to debond over time. Surface sealants can only be recommended for polishing provisional restorations.

Development and characterization of (Ti, Mo)C carbides reinforced Fe-based surface composite coating produced by laser cladding

In this study, in situ multiple carbides reinforced Fe-based surface composite coatings were fabricated successfully by laser cladding a precursor mixture of graphite, ferrotitanium (Fe–Ti) and ferromolybdenum (Fe–Mo) powders. The results showed that (Ti, Mo)C particles with flower-like and cuboidal shapes were in situ formed during the solidification and most shapes of (Ti, Mo)C particles were diversiform according to different contents of Fe–Mo powder in the Fe–Ti–Mo–C system. The growth morphology of the reinforcing (Ti, Mo)C carbide has typically faceted features, indicating that the lateral growth mechanism is still predominant growth mode under rapid solidification conditions. Increasing the amount of Fe–Mo in the reactants led to a decrease of carbide size and an increase of volume fraction of carbides. The coatings had good cracking resistance when the amounts of Fe–Mo were controlled within a range of 15 wt%.

The influence of acid treatment on multi‐walled carbon nanotubes

PurposeThe purpose of this paper is to investigate in detail the effects of acid treatment on multi‐walled carbon nanotubes (MWNTs), which could find a variety of applications in coatings and composites.Design/methodology/approachA number of analytical techniques, including Fourier transform infrared spectroscopy (FT‐IR), X‐ray photoelectron spectroscopy (XPS), Raman spectroscopy (Raman), and scanning electron microscopy (SEM), were employed to assess the effects of acid treatment on MWNTs.FindingsIt was found that desirable modifications to MWNTs occurred after acid treatment. Thus, carboxylic acid groups were introducing on to the surface of MWNTs. It was also found that both chemical and physical properties of MWNTs could be modified/altered.Practical implicationsThe investigation established a method to modify MWNTs via acid treatment and the effects of such a treatment on MWNTs in detail. The modified MWNTs can be used for various applications and further modifications. The acid treated and the further modified MWNTs can be dispersed into polymers to prepare polymer/MWNTs composite materials and composite surface coatings. Some properties of the resulting composites were improved by the dispersed MWNTs, giving excellent mechanical, electrical, thermal and magnetic properties.Originality/valueThe finding on the effects of acid treatment on MWNTs, supported by detailed FT‐IR, XPS, Raman and SEM data, would be of interest to the field. The modification technique provided a route to further modification of carbon nanotubes. The acid treated and the further modified MWNTs are useful for preparation of polymer/MWNTs composite materials and composites surface coatings with improved mechanical, electrical, thermal and magnetic properties.