Study of corrosion and friction reduction of electroless Ni–P coating with molybdenum disulfide nanoparticles

One composite coating of Ni–P alloys containing MoS₂ nanoparticles was prepared by electroless technique based on the better friction reduction ability of MoS₂ and better anticorrosion property of electroless Ni–P alloys on carbon steel surfaces. Electrochemical method—that is, using Tafel polarization curves—was carried out in order to study the corrosion performance of the coating. The results indicate that the anticorrosion ability of the composite coating was decreased because of the addition of nano-MoS₂ particles. The corrosional surfaces were studied and analyzed through scanning electron microscopy (SEM). The corrosion mechanism of the composite coatings was mainly ascribed to the formation of microcells around the nanosized MoS₂ particles, and the active ion-like Cl⁻ destroyed the surface film and induced the corrosion on the inside part of the coating. The friction coefficient of electroless composite coatings was measured by end-facing tribometer. It was found that the friction coefficient of the Ni–P–(nano-MoS₂) composite coating decreased greatly compared with those of Ni–P electroless coatings.     

Electrochemical corrosion and materials properties of reactively sputtered TiN/TiAlN multilayer coatings

TiN/TiAlN multilayers of 2 μm thickness were successfully prepared by reactive DC magnetron sputtering method. XRD pattern showed the (1 1 1) preferential orientation for both TiN and TiAlN layers. XPS characterization showed the presence of different phases like TiN, TiO₂, TiON, AlN and Al₂O₃. Cross sectional TEM indicated the columnar growth of the coatings. The average RMS roughness value of 4.8 nm was observed from AFM analysis. TiN/TiAlN coating showed lower friction coefficient and lower wear rate than single layer coatings. The results of electrochemical experiments indicated that a TiN/TiAlN multilayer coating has superior corrosion resistance in 3.5% NaCl solution.     

Repair of spline shaft by laser-cladding coarse TiC reinforced Ni-based coating: Process,microstructure and properties

To repair the surface defects of spline shaft and improve wear resistance, the coarse TiC reinforced Ni-based composite coatings were fabricated on the spline shaft surface by laser cladding with six types of precursors containing Ni45, coarse TiC, and fine TiN powder. The effects of ceramic content and fine TiN addition on the formability, microstructure, and mechanical properties of the coatings were studied comprehensively. In TiC reinforced Ni-based coatings 1–3 without fine TiN addition, the porosity decreased from 20.415 % to 0.571 % with the increase of TiC concentration. The coatings mainly consist of CrB, Cr7C3, Cr23C6, coarse TiC, and γ-Ni. With the addition of fine TiN, the length of the ceramic phases in coatings 1#–3# decreased slightly, while volume fraction and porosity increased. Moreover, the ring-shaped Ti (C, N) phases were also detected at the edges of both undissolved TiC and TiN particles, which improved the bonding force between ceramics and matrix. Besides, these ceramics inhibited the generation of columnar crystals and eliminated the heat-affected zone. The performance test results show that the coating 3# with 30 wt% TiC and 6 wt% TiN exhibits the best wear resistance despite slightly decreased hardness, and its friction coefficient of 0.409 and wear rate of 42.44 × 10⁻⁶ mm³ N⁻¹·m⁻¹ are, respectively, 0.667 and 0.307 times those of the substrate. Based on the additive/subtractive hybrid manufacturing technology, the optimized coatings were ground to obtain the finishing surface, which indicates that the coarse TiC reinforced coating can be employed in repairing the damaged parts.     

Inhibiting tribocorrosion damage of Cr/CrxN coatings by multi-layer design

The two-layer and multi-layer Cr/Cr_xN coatings were fabricated on 316 L stainless steel (316 L SS) substrates by the arc ion plating technique. The two-layer Cr/Cr_xN coating was a typical CrN coating with an adhesive Cr layer. And the multi-layer Cr/Cr_xN coating design was in two dimensions. In the first dimension, the multi-layer Cr/Cr_xN coating consisted of alternative Cr/CrN layers with the thickness ratio of 1:5; in the second dimension, the alternative Cr₂N layers with the thickness of 10 nm were inserted in CrN layers. This design was expected to increase transverse interfaces in a smaller scale. The microstructures, mechanical, corrosion and tribocorrosion performances of both Cr/Cr_xN coatings were systematically investigated. The results showed that the special multi-layer design of Cr/Cr_xN coatings improved mechanical, anti-corrosion and anti-tribocorrosion performances. Compared with the two-layer Cr/Cr_xN coating, the reduced tribocorrosion damage of the muti-layer Cr/Cr_xN coating was closely related to the inhibited synergistic effect between electrochemical corrosion and mechanical wear. In conclusion, the multi-layer Cr/Cr_xN coating was more suitable to work as the surface protective coating than the two-layer Cr/Cr_xN coating in seawater.     

Preparation and investigation of pulse co-deposited duplex nanoparticles reinforced Ni-Mo coatings under different electrodeposition parameters

In this work, Ni–Mo–SiC–TiN nanocomposite coatings were deposited on aluminium alloy by pulse electrodeposition with various electrodeposition parameters. The influences of the pulse frequency and duty cycle on the phase structure, morphology, mechanical and corrosion performance of the coatings were systematically investigated. The results showed that with increasing pulse frequency and decreasing duty cycle, the content of embedded duplex nanoparticles increased, and the grains refined gradually. The nanocomposite coating that was prepared at 20% duty cycle and 1000 Hz pulse frequency exhibited compact, uniform, and fine microstructures with the maximum incorporation of nanoparticles (6.81 wt% TiN and 1.72 wt% SiC). The wear rate and average friction coefficient then declined to 4.812 × 10^?4 mm³/N·m and 0.13, respectively, with a maximum microhardness of 519 HV. Simultaneously, the corrosion current density was reduced to 3.11 μA/cm², and a maximum impedance of 34888 Ω cm² was exhibited. The uniformly distributed duplex nanoparticles acted as a hindrance, which consequently supported the enhancement of corrosion and wear resistance. By investigating the variation of the pulse diffusion layer with electrical parameters, it was discovered that when the crystallite size is equivalent to or smaller than the diffusion layer thickness, it would be easier to cross the diffusion layer to incorporate in the coating. Additionally, the effects of various duty cycles and pulse frequencies on the nucleation process of the grains were discussed.     

Mechanical,biocorrosion, and antibacterial properties of nanocrystalline TiN coating for orthopedic applications

The current study analyzes the surface, mechanical, biocorrosion, and antibacterial performances of a nanocrystalline TiN ceramic coating synthesized using cathodic arc-physical vapor deposition (PVD) on biomedical Ti6Al4V substrates. The surface hardness and modulus of elasticity were assessed using the microindentation method. The adhesion, friction coefficient, and antibacterial properties of the coating were evaluated. The in vitro corrosion of the prepared coated Ti alloy substrate was analyzed in simulated body fluid (SBF) via cyclic potentiodynamic polarization (CPP), dynamic electrochemical impedance spectroscopy (DEIS), and scanning vibrating electrochemical technique (SVET). The results demonstrated that a nanocrystalline TiN coating with a crystallite size of 10.33 nm and a thickness of 5 μm was formed with good adhesion on the alloy surface. The coating had an enhanced surface hardness of 38.63 GPa and a modulus elasticity of 358 GPa, and exhibited enhanced resistance to plastic deformation compared with the substrate – features that can enhance the service life of an implant. The antibacterial experiments indicated an upgraded antibacterial performance of the TiN coating compared to the bare alloy. The in vitro corrosion-resistance analyses confirmed the enhanced surface protective performance of TiN ceramic coatings against biocorrosion in SBF. The results showed higher impedance values in DEIS, a higher passive region in the CPP analysis, and a lower anodic current density in the SVET analysis compared with the bare substrate.     

Corrosion and friction resistance of TiVCrZrWNx high entropy ceramics coatings prepared by magnetron sputtering

High entropy alloy coatings have attracted much attention because of their high hardness, low-level fault energy, and chemical stability. Nevertheless, this type of coating would inevitably suffer from wear, corrosion, aging, and so on. Hence, a novel coating with corrosion and friction resistance would be constructed for broadening its application scenarios. In this work, TiVCrZrWN_x high entropy ceramics coatings were prepared by reactive magnetron sputtering. The microstructure, mechanical properties, friction, and corrosion resistance of the coatings deposited at different nitrogen flow rates have been studied. The microstructure of TiVCrZrWN_x coatings is strongly dependent on the nitrogen flow rate and forms a stable FCC structure when the nitrogen flow rate reaches 24 sccm. The pure TiVCrZrW coating is 15.65 GPa, with the increase of nitrogen flow rate (24 sccm), the coating hardness reaches 21.27 GPa. The corrosion resistance of the coatings also increases continuously. According to the results of the impedance spectrum and polarization curve, the charge transfer resistance value of the coating gradually increases with the content of nitrogen, the current density rapidly decreases to a minimum as the potential increases. In terms of tribological behavior, the formation of V₂O₅ during the sliding in seawater could significantly reduce the coefficient of friction from 0.603 to 0.383. Therefore, TiVCrZrWN_x HECs coatings simultaneously possess high hardness, toughness, and excellent resistance to friction and corrosion, which is expected to provide a new and reliable method for the research field of coatings in the maritime field.     

Influence of nitrogen gas over microstructural,vibrational and mechanical properties of CVD Titanium nitride (TiN) thin film coating

In this experimental investigation, the influence of different N₂ gas flow rates on different properties (e.g. morphological, mechanical, etc.) of chemical vapor deposited (CVD) Titanium nitride (TiN) coatings has been discussed. The TiN coatings had been grown on Si (100) substrate at elevated temperature (1000 °C) using Titanium dioxide (TiO₂) powder. SEM images reveal a dense uniform microstructure with an irregular surface pattern. The surface roughness of the coatings was found to be increased from 12.42 to 28.56 nm with an increase in flow rate. XRD results indicate a B1 NaCl crystal structure of the film with reduced crystallite size with the increasing N₂ flow rate. Through the corrosion test, it has been observed that due to the variation of N₂ flow rate the corrosion resistance of the films decreases with increasing N₂ flow rate. The mismatch of thermal expansion co-efficient in between Si substrate and TiN thin film reduces with higher N₂ flow rate. The acoustic and optic phonon mode of TiN coatings have been shifted to higher intensities with higher N₂ flow rate. The mechanical properties of the film reveal that the maximum value of hardness (H) and Young's modulus (E) are 30.14 and 471.85 GPa respectively.     

Tribocorrosion characteristics of CrMoSiCN/Ag coatings on Ti6Al4V alloys in seawater

CrMoSiCN/Ag coatings were deposited on Ti6Al4V alloys at the trimethylsilane flow of 15 sccm using closed-field unbalanced magnetron sputtering, and their microstructures were observed and analyzed using SEM, XRD, XPS and TEM, respectively. The coatings’ mechanical properties were measured using nano-indenter. The tribocorrosion characteristics of Ti6Al4V and CrMoSiCN/Ag coatings were investigated in seawater using tribocorrosion tester. The results revealed that the nanocomposite coatings consisted of (Cr, Mo)N solid solution, Ag nanocrystal and amorphous SiCN_x matrix. As the Ag target current increased to 1.0 A, a large amount of Ag nanoparticles were observed on the coating surface. The coating hardness initially increased to 21.0 ± 0.7 GPa at the Ag target current of 0.4 A and then declined. After the Ag element was added into coatings, their tribocorrosion characteristics were improved. The tribocorrosion characteristics of coatings were much better than those of Ti6Al4V. The tribocorrosion characteristics of CrMoSiCN/Ag coating at the Ag target current of 1.0 A were the best in seawater.     

Characterisation of in-situ reactive plasma-sprayed nano-(Ti,V)N composite ceramic coatings with various V concentrations

The effect of V concentration on the microstructure and phase composition of nano-(Ti, V)N composite ceramic coatings prepared by in-situ reactive plasma spraying of mechanically mixed Ti–V powders were investigated using X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, X-ray energy dispersive spectroscopy, and transmission electron microscopy. The microhardness, toughness, wear resistance, and strengthening mechanism of the prepared nano-(Ti, V)N coatings were measured and analysed. The results showed that the nano-(Ti, V)N coating comprised a large proportion of nano-(Ti, V)N grains, which was the solid solution of TiN and VN. All the V atoms completely entered the TiN lattice and the solubility limit of V in TiN is approximately 25 wt%. The grains of the (Ti, V)N (25 wt% V) coating had a face-centred cubic structure and a large quantity of twins; they were primarily equiaxed grains morphology with a few columnar grains. From comparing the experimental statistics, the (Ti, V)N (25 wt% V) coating displayed the highest microhardness (1952 ± 78.5 Hv) and the most even dispersion but a slightly lower toughness compared with the (Ti, V)N (35 wt% V) coating. The (Ti, V)N (25 wt% V) coating with a dense microstructure obtained a high microhardness due to dislocation strengthening, fine grain strengthening, and solid solution strengthening (from the solid solution of VN in TiN). Furthermore, a lower friction coefficient and wear volume loss indicated that the (Ti, V)N (25 wt% V) coating had superior tribological properties and great potential as a wear resistant coating.     

Growth,mechanical properties,and tribological performance of TiAlN/NbN and NbN/TiAlN bilayer coatings

Three different coatings, namely TiAlN, TiAlN (external)/NbN (internal) and NbN (external)/TiAlN (internal), were deposited on cemented carbides by arc ion plating. The comparative investigation conducted in this study elucidates the effect of the NbN layer and coating systems on the growth, mechanical properties, and tribological performance of the coatings. The results showed that the surface of the TiAlN and TiAlN/NbN coatings was smoother when TiAlN served as the external layer. The NbN/TiAlN coating, wherein NbN formed the external layer, had a much rougher but more symmetrical surface. With the introduction of the NbN layer, the increased micro stress induced a lower adhesion strength in the TiAlN/NbN and NbN/TiAlN coatings. The TiAlN/NbN and NbN/TiAlN coatings exhibited higher hardness and hardness/effective elastic modulus (H/E*). During the friction test, when the temperature was elevated to 700 °C, the tribological performance of the monolayer TiAlN coating was the lowest because of the TiO₂-induced breakage of the dense tribo-oxide film. The NbN layer participated in the formation of a NbO_x film at elevated temperatures, which was responsible for the high tribological performance of the two bilayer coatings. When the NbN layer was on the outermost layer and in direct contact with the elevated temperature atmosphere, the NbN/TiAlN coating generated a tribo-oxide film with high integrity, and its coefficient of friction decreased by 27% of that at room temperature. Therefore, the NbN/TiAlN coating exhibited the highest wear resistance at 700 °C.     

Tribological study of amorphous BC4N coatings

Amorphous BC₄N thin films with a thickness of ∼ 2 μm have been deposited by Ion Beam Assisted Deposition (IBAD) on hard steels substrates, in order to study the wear behavior under high loads and the applicability as protective coatings. The bonding structure of the a-BC₄N film was assessed by X-ray Absorption Near Edge Spectroscopy (XANES) and Infrared Spectroscopy, indicating atomic mixing of B–C–N atoms, with a proportion of ∼ 70% sp² hybrids and ∼ 30% sp³ hybrids. Nanoindentation shows a hardness of ∼ 18 GPa and an elastic modulus of ∼ 170 GPa. A detailed tribological study is performed by pin-on-disk tests, combined with spectromicroscopy of the wear track at the coating and wear scar at pin. The tests were performed at ambient conditions, against WC/Co counterface balls under loads up to 30 N, with the sample rotating at 375 rpm. The coatings suffer a continuous wear, at a constant rate of 2 × 10^− 7 mm³/Nm, without catastrophic failure due to film spallation, and show a coefficient of friction of ∼ 0.2.     

Effects of graphene content in alkaline silicate electrolyte on AA1060 pure aluminum micro-arc oxidation coating

Ceramic coatings were obtained by micro-arc oxidation (MAO) on the surface of AA1060 pure aluminum in alkaline silicate electrolyte with the addition of graphene. The effects of graphene contents in the range of 0–.30 g/L in the electrolyte on surface morphology, corrosion resistance, and wear resistance of the ceramic coatings were investigated. The outer surface structure, outer surface element content, coating cross-section structure, coating cross-section element content, coating/substrate interface structure, and coating phase were characterized by scanning electron microscope and X-ray diffraction. Potentiodynamic polarization and electrochemical impedance spectroscopy were used to evaluate the corrosion behavior of MAO samples in a 3.5-wt% NaCl solution. In addition, the resistance to sliding and abrasive wear of the oxide coating were studied experimentally. The results show that the alkaline silicate electrolyte with the addition of graphene has a significant effect on the characteristics of MAO coating. The performance of micro-arc oxide coatings is best when the graphene content in the electrolyte is .15 g/L, the average thickness of the film is 7.24 μm, the average pore size is 6.07 μm, the impedance value is approximately 4.01 × 106 Ω, and its friction coefficient is .55.     

Microstructural,mechanical and tribological properties of carbon nanotubes reinforced plasma sprayed molybdenum disulphide composite coatings

The development of 1-Dimensional (1D) and 2-Dimensional (2D) materials have gained considerable attention towards achieving solid-state lubricity. Herein, we present the effect of carbon nanotubes (1D) reinforcement into the molybdenum disulphide (2D) coatings. Plasma sprayed MoS₂ coatings reinforced with 2-4 wt% CNTs were fabricated using shroud plasma spraying over steel substrates. The shroud attachment envelops the plasma plume and cut down its exposure to surroundings, which minimizes the oxidation of MoS₂ powder during spraying. The microstructural analysis revealed the presence of MoS₂ and CNTs in the composite coating. The mechanical hardness and elastic modulus of MoS₂ coating improved by 2–3 folds in the composite coating. In tribological performance, the coefficient of friction (COF) decreased from 0.13 to 0.07 in M2C coating. The wear weight loss was estimated as 0.89 ± 0.07 mg, 0.18 ± 0.02 mg and 0.39 ± 0.03 mg for M, M2C and M4C coatings respectively. It can be attributed that tubular CNTs acted as bearing on MoS₂ layers. This work opens an impressive stepping for the synergistic mixture of 1D (CNTs) and 2D (MoS₂) material to obtain high-quality wear-resistant coatings.     

Tribochemistry of TiN films sliding against ceramic counterparts in vacuum condition and N2 atmosphere

With the rapid development of aerospace technology, the tribological performance of moving parts under extreme operating conditions has attracted a great deal of attention and interest. The application of solid lubricant coatings has become a major means of improved performance to ensure stable operation. Although molybdenum disulfide (MoS₂) and diamond-like carbon (DLC) films have excellent low coefficients of friction, they are prone to failure in vacuum because they cannot overcome the challenges of assembly in atmospheric environments. Surprisingly, unexpected results were obtained in this study using conventional nitride films. Specifically, the friction coefficient of TiN/SiC friction pair in vacuum is 0.21 and the wear rate is 8.8 × 10^?7 mm³/mN. The relatively stable friction coefficient is mainly attributed to the formation of carbonaceous lubricating layer at the interface, which is the decisive factor in reducing wear. The friction coefficient of TiN/WC friction pair under N₂ atmosphere is 0.31 and the wear rate is 4.5 × 10^?7 mm³/mN. It can be summarized as follows: first, the mechanochemical induced chemical reaction of the interface, and secondly, the thermally excited nitrogen atoms saturate the dangling bonds of the transfer film. The results further reveal the friction mechanism of TiN films with advanced ceramic materials under harsh conditions and suggest a guide for engineering applications.     

Electrodeposition and tribocorrosion behaviour of ZrO<Subscript>2</Subscript>–Ni composite coatings

With the objective of producing new functional surfaces with enhanced tribo-corrosion properties we have investigated the electrochemical codeposition of composites in which an electrodeposited metal (nickel) is the matrix and a transition metal oxide (ZrO₂) is the dispersed phase. This paper describes the effect of ZrO₂ dispersed particle codeposition on nickel electrocrystallisation steps as well as the tribocorrosion behaviour of the composite coatings obtained. This system was selected because nickel is an industrially important coating material on steel and other support materials. The cathodic polarization curves have been plotted both in the presence and absence of the insoluble dispersed phase. Electrochemical impedance spectroscopy was used to obtain additional information on the early steps of nickel and nickel matrix composite electrodeposition. Impedance data were acquired with a Solartron type electrochemical interface and frequency response analyzer. A schematic codeposition mechanism is proposed. The influence of zirconium oxide on the nickel electrodeposition steps is discussed. The tribocorrosion properties of ZrO₂–Ni composite coatings (100 μm thickness) have been studied in 0.5 M K₂SO₄ solution on a pin on disc tribo-corrosimeter connected to an electrochemical cell. The normal force applied was 10 N at a rotation speed of 120 rpm. The counterbody (pin) was a corrundum cylinder (7 mm in diameter), mounted vertically on a rotating head, above the specimen. The lower spherical end (radius = 100 mm) of the pin was then applied against the composite surface (disc).     

Tribomechanical and microstructural properties of cathodic arc-deposited ternary nitride coatings

Sintered carbides are promising materials for surfaces that are exposed to extreme wear. Owing to their high service load, ceramic-based thin films are coated on carbides using different techniques. In this study, non-toxic and cobalt-free powder metallurgy-sintered carbide samples were coated with TiN, TiAlN, CrAlN, and TiSiN ceramic-based thin film coatings by cathodic arc physical vapor deposition. The microstructure (phase formation, coating thickness, surface roughness, and topography), mechanical properties (hardness, modulus of elasticity, and plasticity indices), and tribological properties (nanoscratch and wear behavior) of the thin film coatings were investigated. No cracks or defects were detected in these layers. The ceramic-based ternary nitride thin film coatings exhibited better mechanical performance than the TiN coating. The TiN thin film coating had the highest average surface roughness, which deteriorated its tribological performance. The ternary nitride thin film coatings exhibited high toughness, while the TiN thin film coating exhibited brittle behavior under applied loads when subjected to nanoscratch tests. The wear resistance of the ternary nitride coatings increased by nearly 9–17 times as compared to that of the TiN coating and substrate. Among all the samples investigated, the substrate showed the highest coefficient of friction (COF), while the TiSiN coating exhibited the lowest COF. The TiSiN thin film coating showed improved mechanical and tribological properties as compared to other binary and ternary nitride thin film coatings.     

Tribological behavior of the polyamide composite coating filled with different fillers under dry sliding

The polyamide (PA) composite coating filled with the particles of microsized MoS₂, microsized graphite, and nano‐Al₂O₃, respectively, were prepared by flame spraying. The friction and wear characteristics of the PA coating and composite coating filled with the varied content of filler under dry sliding against stainless steel were comparatively investigated using a block‐ring tester. The morphologies of the worn surfaces and transfer films on the counterpart steel ring were observed on a scanning electron microscope. The result showed that the addition of fillers to the composite coatings changed significantly the friction coefficient and wear rate of the coatings. The composite coatings filled with a low level content of fillers showed lower wear rate than did pure PA coating under dry sliding; especially the MoS₂/PA composite coating had the lowest wear rate among these composite coatings. The composite coatings with a high level content of fillers had higher wear rate than did pure PA coating, except of the Al₂O₃/PA composite coating. The bonding strengths between the polymer matrix and fillers changed with the content of the fillers, which accounted for the differences in the tribological properties of the composite coatings filled with the varied content fillers. On the other hand, the difference in the friction and wear behaviors of the composite coatings and pure coating were attributed to the difference in their worn surface morphologies and transfer film characteristics. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Ternary hydroxyapatite/chitosan/graphene oxide composite coating on AZ91D magnesium alloy by electrophoretic deposition

In this work, ternary HA/chitosan/graphene oxide (GO) coating was applied via electrophoretic deposition on AZ91D magnesium alloy as bone implants, successfully. Subsequently, phase composition, surface morphology, hardness, corrosion behavior, bioactivity and antibacterial of the composite coatings were studied. Hardness and Young's modulus of the composite coatings increased from 40 ± 1.5 MPa and 3.1 ± 0.42 GPa to 60 ± 3.12 MPa and 8 ± 0.53 GPa for composite coatings with 0 and 2 wt% GO, respectively. The results of the SBF solution soaking of the composites after 24 days, indicated the improvement of HA growth due to the increasing of the GO addition in composite coating. New HA grains with leaf-like morphology grew uniformly at higher amounts of GO (1 and 2 %wt) in a perfectly balanced composition. Rate of the substrate corrosion significantly decreased from 4.3 to 0.2 (mpy), when the amount of GO increased from 0 to 2 wt% due to reduction of the surface cracks at the presence of the GO reinforcement. Also, there was no Escherichia coli and Staphylococcus aureus bacteria growth in broth medium after 24 h and OD₆₀₀ results at 24 h post inoculation for the 2%wt GO addition in coating.