Role of Sn on the adhesion in Cu–Sn alloy-coated steel–rubber interface

Cu–Sn coatings with varying Sn content were deposited on steel substrate by immersion route and the effect of variation of Sn content and the substrate roughness on the interfacial adhesion strength of Cu–Sn-coated steel substrates vulcanized with styrene butadiene rubber were investigated. The surface roughness of the coatings did not vary compared to pristine steel substrate with change in Sn weight% in the coatings. The coated surfaces exhibited bare spots or deep trough as micro-discontinuities in the coatings, where formation of Fe₂O₃ was evident from SEM-EDS, AES, and XPS analysis. Microstructural study of the coating cross-section and coating-substrate interface by transmission electron microscopy of cross-sectioned samples revealed inadequate penetration of coating inside these troughs. Peel test carried out on the Cu–Sn-coated steel–rubber joints showed mixed mode i.e. adhesive and cohesive mode of interfacial fracture irrespective of the coating composition. The peel test further indicated higher interfacial adhesion strength for Cu–Sn-coated samples than pure Cu-coated samples, with an optimum adhesion strength for the coatings containing 3–4?wt.% Sn.     

Adhesion of Vacuum Deposited Optical Coatings on PMMA and Polycarbonate

Abstract

The deposition of interference coatings with optical functions (e.g., anti-reflective coatings, beam splitters and filters) on plastic substrates is becoming ever more important. A well-known deposition method for such coatings on polymers is plasma ion-assisted vacuum evaporation (plasma ion-assisted deposition or plasma IAD). However, the industrial production of well-adhering dielectric coatings on unlacquered polymer surfaces has not yet been developed to a satisfactory level. PMMA is known to be extremely difficult to coat with optical layers because of its inadequate adhesion characteristics. Polycarbonate is considered to be less problematic, but in many cases unexpected adhesion failures arise. This paper presents a study of the reasons for the poor adhesion to PMMA of oxide coatings deposited by plasma IAD. We show that in such a coating process it is only the exposure of the substrate to particles and short-wavelength radiation that determines its adhesion to the deposited layer. For polycarbonate, we found a dependence of the adhesion strength of the coating on its porosity. Considering these results, modified plasma IAD processes have been developed that enable the deposition of well-adhering optical coatings on these polymers.     

Effects of size, shape and floatage of Cu particles on the low infrared emissivity coatings

Low infrared emissivity coating was prepared by the copper (Cu) particles and ethylene–propylene–diene monomer (EPDM) binder. The effect of size, shape and floatage of Cu particles on infrared emissivity of the coatings was systematically investigated. The results indicated that the optimized Cu particles with the minimum coating emissivity are several micron-sized, flaky and high-leafing, exhibiting 0.78, 0.72 and 0.10 emissivity value, respectively. The formation of low infrared emissivity coatings depends strongly on the floatage of Cu particles, not the size or shape, and the results obtained by leafing aluminum (Al) and bismuth oxide (Bi₂O₃) pigment are in good agreement with this standpoint. A theoretical model was proposed to account for the mechanism, which indicated that the low porosity of the coatings with leafing pigments plays an important role in the formation of low emissivity coatings.     

Preparation and adhesion performance of multilayered Ni coatings deposited by ultrasonic-assisted electroplating

The multilayered Ni coatings were successfully obtained by introducing the periodic ultrasonic wave into the ordinary electroplating process. The bidirectional bend method is proposed to assess the adhesion performance of electroplated Ni coatings to the substrate. The results show that the multilayered Ni coatings show much better adhesion performance than that of the ordinary Ni coatings. The application of ultrasonic causes a strong modification in the growth orientation of Ni crystallites in the coating, to promote the growth of nickel layers in the manner parallel to the substrate surface, namely (111) growth orientation.     

Strontium and copper co-substituted hydroxyapatite-based coatings with improved antibacterial activity and cytocompatibility fabricated by electrodeposition

Bacterial infection are serious complications for biomedical implants in the orthopedic and dental fields, and the ideal implants should combine good antibacterial ability and bioactivity. In this paper, we have fabricated the strontium/copper substituted hydroxyapatite (SrCuHA) coating on the commercially pure titanium (CP-Ti) and studied their effect on antibacterial and in vitro cytocompatible properties. Cu was incorporated into HA in order to improve its antimicrobial properties. Sr was added as a second binary element to improve the biocompatibility. The structural and morphological characteristics of the SrCuHA coatings were investigated using various analytical techniques. The presence of Sr²⁺ and Cu²⁺ in solution led to reduced roughness of the coating and finer nucleus size formed. The results highlight that Sr²⁺ and Cu²⁺ were homogenously incorporated into HA lattice to form SrCuHA coatings. Inductively coupled plasma mass spectrometry (ICP-MS) was used for the leach out analysis of the samples. A low contact angle value revealed the hydrophilic nature. In vitro electrochemical corrosion studies indicated that the SrCuHA coating sustain in the stimulated body-fluid (SBF), exhibiting superior corrosion resistance with a lower corrosion penetration rate than the bare CP-Ti substrate. The SrCuHA coatings can kill Escherichia coli to a certain extent during the first few days, which might be due to the Cu substitution in the coating. An enhancement of in vitro osteoblast adhesion, proliferation, and alkaline phosphatase activity was observed, which could lead to the optimistic orthopedic and dental applications.     

Barrier and adhesion properties of anti-corrosion coatings based on surfactant-free latexes from anhydride-containing polymers

We have successfully obtained surfactant-free latexes from anhydride-containing polymers, including poly(styrene-alt-maleic anhydride) (PSMA), maleinized polybutadiene (PBDMA), and poly(octadecene-alt-maleic anhydride) (POMA). Here we report barrier and adhesion properties of the coatings made from these surfactant-free latexes, which were crosslinked with adipic acid dihydrazide (ADH). The barrier property of these coatings was studied with electrochemical impedance spectroscopy in NaCl solutions on pretreated aluminum substrates. PSMA and PBDMA-based coatings demonstrated good barrier property, indicated by the absence of corrosion after 1-month immersion in NaCl solutions, which was comparable to that of a commercially available polyester coating. The polyester coating, however, was found to hydrolytically degrade when immersed in a NaCl solution, which was not observed for our latex-based coatings. The POMA-based coating showed inferior barrier property on un-pretreated aluminum, likely due to inhomogeneous film formation and poor adhesion to the substrate, but the adhesion could be improved by an alkali pretreatment of the substrate. In comparison, PBDMA and PSMA-based coatings showed much better adhesion toward the aluminum substrates. The anti-corrosion behavior appeared to be closely related to both the barrier and adhesion properties of the coatings on the metal substrate.     

Adhesion measurement of interfaces between gelatin and poly(ethylene terephthalate) using microscratch technique

A microscratch technique was used to evaluate the adhesion between interfaces of a gelatin coating and poly(ethylene terephthalate) (PET) film. The interface was reinforced by nitrogen plasma treatment on the PET surface and subsequently by heat treatment of each gelatin/PET sample to promote interactions at the interface. In the microscratch test, a normal load controlled conical stylus with 50‐μm radius tip was drawn over the gelatin coating surface under a continuously increasing normal load until failure occurred in the sample. Optical microscopy and depth profiling of the scratch track were used to detect failure and the failure mechanism. The critical normal load (F_c) was defined as when gelatin detached from the PET substrate or when a complete removal or plowing of the gelatin coating on the PET substrate occurred. With increasing plasma treatment time and heating treatment temperature, the F_c for both debonding and coating removal increased, which showed that both failure mechanisms are related to the adhesion. Different thicknesses of the gelatin coatings were also prepared under the same plasma and heat treatment conditions. It was found that the F_c increased with increasing coating thickness. The result demonstrated that both failure mechanisms depended on the plastic deformation of the coating and substrate. The F_c for coating detachment increased linearly with increasing coating thickness whereas the F_c for coating removal increased sharply with increasing thickness. Annealing temperatures ranging from 20 to 80°C exhibited a strong effect on the F_c, which increased with increasing annealing temperature. These results demonstrate that the microscratch technique can be used to access interfacial adhesion and that the F_c is a qualitative parameter for the evaluation of adhesion strengths. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1960–1974, 2006     

Preparation of a hydrophobic cerium oxide nanoparticle coating with polymer binder via a facile solution route

In this work, cerium oxide (CeO₂) nanoparticles (NPs) were synthesized using a facile, low temperature solution process and coated using spin coating and spray coating approaches, for the fabrication of a hydrophobic surface coating. Silicon wafer (Si) substrates coated with CeO₂ NPs exhibited excellent hydrophobic behavior, but poor adhesion of the NPs to the substrate was observed - likely due to the low surface polarity of CeO₂ NPs. Polyacrylic acid (PAA) was introduced as an adhesion promoter to improve NP surface characteristics and obtain an adherent and cohesive coating. Slight polarity tuning and binder inclusion significantly enhanced the binding capability of the NPs as determined by peel-off measurements. The superior mechanical properties of NP coatings were attributed to the incorporation of PAA in the polymeric network. It improves inter-particle and particle-substrate secondary interactions, ultimately aiding NP cohesion and adhesion when deposited onto the Si substrate. The adhesive and hydrophobic properties of CeO₂ NP coatings were maintained upon exposure to high temperatures, and the coatings are transparent as well, making them suitable for various applications, such as cookware, glass coating and technology components.     

Quantitative measurement of adhesion between polypropylene blends and paints by tensile mechanical testing

A tensile mechanical test suiable to measure the adhesion between brittle coatings and ductile substrates was applied to measure the adhesion of painted layers on polypropylene blends. The test involves the tensile deformation of the painted assembly, resulting in the periodic cracking of the brittle coating on the ductile substrate. The interfacial shear strength was determined by measuring the strength of the coating, the thickness of the coating, and the average width of paint fragment after the crack density reaches saturation. Apparent interfacial shear strength was obtained for different paints on the same kind of blend, which gave consistent results over the experimental strain rate range from 10^?4 to 10^?3 sec^?1. Interfacial delamination was studied by optical microscopy (OM) and transmission electron microscopy (TEM). The delamination was observed to mainly occur near the adhesion promoter and substrate interface.     

AFM Scratching for Adhesion Studies of Thin Polymer Coatings on Steel

Abstract

Atomic force miscroscopy (AFM) scratching at constant applied forces was used to quantify the adhesion of polymer coatings to cold rolled steel (CRS) and to study the effectiveness of a pretreatment for improving the adhesion. The pretreatment was a phosphate-free zirconia-based coating. Thin layers of commercially available epoxy, acrylic and polyester-based polymer coatings, were applied to polished or pretreated cold rolled steel substrates and the surface was scratched at the edge of the polymer coatings with the AFM tip at increasing values of normal loads until the coating was removed. Adhesion strengths were determined from the minimum tip-sample interaction force and number of cycles (scans) at a particular applied force. The pretreatment significantly improved adhesion of the epoxy and acrylic-based coatings on CRS. Adhesion of the acrylic-based coating was found to be better than the epoxy coatings on the bare as well as pretreated steel. Adhesive strength of the polyester-based coating was inconclusive because it was very easily removed on application of small forces using the AFM tip. The AFM scratching technique was found to provide a quick, easy and effective way to make quantifiable comparisons in relative adhesive strengths of polymer coatings and the effect of pretreatments.     

Surface metallization of Cu/Ni/Au coatings on diamond/Cu composite materials for heat sink application

Electroless-plating and electro-plating have been used to deposit Cu-Ni-Au coating on diamond/Cu composites. Before electroless copper plating, pretreatment should be applied to the surface of composites by means of boiled HNO₃ etching, sensitization with SnCl₂ and activation with PdCl₂. The influence of pre-treatment on the electroless copper plating and electroplating Ni/Au is studied in this paper. Scanning electronic microscope, energy dispersive spectroscopy and optical microscope are used to examine microstructure and morphologies of coatings. Results indicated that the uniform and tight bonded Cu/Ni/Au coating have been successfully deposited on the diamond/Cu composites. Meanwhile, high temperature baking, solder wetting and the polarization curve tests are used to evaluate the adhesion strength, solderability and corrosion resistance of Cu/Ni/Au coatings in detail. Investigated results indicated that diamond/Cu covered with Cu-Ni-Au coatings exhibited excellent solderability and mechanical properties.     

Effect of copper pretreatment on the zincate process and subsequent electroplating of a protective copper/nickel deposit on the AZ91D magnesium alloy

To obtain a durable Ni coating with excellent adhesion strength on an AZ91D Mg alloy, a pretreatment was performed with a small amount of Cu²⁺ ions added to the activation bath used in the pretreatment prior to the plating process. In the pretreatment activation process, a high density Cu layer was deposited on both the α-phase and β-phase areas of the substrate accompanied with Mg dissolution. The Cu deposit acted as nucleation seeds for the Zn deposition in the following zincate process which provided a uniform and dense Zn layer almost completely covering the substrate. Then a thin Cu layer was electroplated on this zincated substrate as an undercoating for the succeeding electroplating with Ni. Cross-sectional scanning electron microscopy observations showed that the Cu deposited by the pretreatment enabled the deposition of a protective Ni layer with few defects. This structure also contributed to the improvement of adhesion strength and corrosion resistance as compared with the non-Cu added sample.     

Fabrication of functionally graded Fe-TiC wear resistant coating on CK45 steel substrate by plasma spray and evaluation of mechanical properties

The main challenge in production of metal matrix composite coatings is the existence of thermal residual stress in coating – substrate interface which results in delamination of the coating eventually. The aim of this paper is to enhance the tensile bond adhesion of the coating by fabricating functionally graded coating. In this regard, raw materials including titanium carbide and iron powders were milled with different compositions. From the substrate to the surface, the weight fraction of TiC particulates increased from 25% to 100%, while the weight fraction of Fe particulates decreased in mentioned direction. Moreover to make a comparison between mechanical properties of the graded coating with those of duplex and single layer coatings, a coating system comprising NiCrAlY bond coat and 100?wt% TiC top coat and a single layer titanium carbide coating were prepared as well. X-Ray diffraction method was used to identify obtained phases from each composition. In addition, microstructural properties of the coatings were investigated by scanning electron microscope. Mechanical properties such as adhesion, hardness and wear resistance were evaluated by tensile bond test, Vicker's method and pin- on- disc method, respectively. The results revealed that the FGC sample has higher coating adhesion in comparison with other coating. Moreover the wear test results showed that the FGC sample faced with less weight loss which means higher wear resistance.     

Microstructure and fracture toughness of in-situ nanocomposite coating by thermal spraying of Ti3AlC2/Cu powder

The low fracture toughness of ceramic coatings has always hindered their wide application. In this study, an in-situ nanocomposite coating was prepared by the atmospheric plasma spraying of a 50 wt% Ti₃AlC₂-50 wt% Cu mixed powder. The in-situ nanocomposite coating was found to have an unusual microstructure with a nano-micrometre phase synergistic enhancement, which consisted of submicrometre-thick layers of Cu and nanoparticles of Cu(Al), Ti₄O₅, TiO₂, and Al₂TiO₅. Thus, in the spraying process, Al was delinked out of Ti₃AlC₂, forming a large amount of plastic Cu(Al) with Cu. The delinked channel provided a path for Cu to diffuse into Ti₃AlC₂, which a spatial Cu network structure was formed in the coating. The in-situ nanocomposite coating has high fracture toughness and crack growth resistance by a three-point bending test. This paper reports a new method to prepare a high-fracture-toughness composite ceramic coating.     

Effect of substrate rotational speed during deposition on the microstructure,mechanical and tribological properties of a-C:Ta coatings

Rotational speed has an important influence on the performance of coating materials. The a-C:Ta composite coatings were prepared by controlling the substrate rotational speed during deposition process using PVD technique. The results showed that the coating transformed from dense structure to columnar structure. Due to the changes of deposition time and the vapor incident angle of the sputtering ions, the sp² hybrid structure increased and the C–Ta bonds contents decreased as a function of the rotational speed, which led to the improvement of adhesion force. The average friction coefficient of the composite coatings did not fluctuate significantly for the amorphous carbon matrix and the transfer films formed during friction, while the wear rates were gradually increased. The sample at 0.5 rpm possessed the lowest wear rate, which was mainly associated with the cooperative behavior of the dense structure and the formation of TaC nanoclusters in the composite coating.     

Microstructure,mechanical and tribological properties of Mo–V–Cu–N coatings prepared by HIPIMS technique

A combination of high wear-resistance and low-friction is crucial for improving the wear performance of self-lubricating coatings, which is generally determined by an excellent lubricating effect and mechanical strength. In this study, the Mo–V–Cu–N coatings were prepared by HIPIMS technique with a spliced target of Mo–V–Cu at various charge voltages. The results revealed that Mo–V–Cu–N coatings presented a solid solution phase of B1–MoVN with (200) preferred orientation, and the preferred orientation was enhanced at high charge voltages. Whereas the Cu atoms formed an amorphous phase in Mo–V–Cu–N coatings due to a low Cu content of 2.3–3.6 at.%. As the charge voltage increased to 750 V, more charged metallic ions were accelerated and bombarded substrate surface efficiently, forming smooth and dense Mo–V–Cu–N coatings with a high hardness of 31.0 GPa. All the coatings presented a low friction coefficient of 0.34–0.39 due to the formation of MoO₂, VO₂ and CuO mixed oxides, and the wear mechanism was dominated by abrasive and tribo-oxidation wear at room temperature.     

Microstructural evolution and micromechanical properties of thermally sprayed hydroxyapatite coating

ABSTRACT

The effects of preheating and annealing processes on the micromechanical features of thermally sprayed hydroxyapatite (HA) coatings were investigated. The results indicated that subsequent heat treatment at 700°C for 60?min promotes the development of a crystalline HA coating. The EDS line scan showed that the oxygen content was homogeneous along the thickness direction from the coating surface to the titanium–HA interface, whereas the calcium and phosphorus concentration gradually decreased at 7?μm from the interface. From the roughness profiles, the coatings on preheated substrates gave lower roughness compared to the coatings at room temperature. According to the nanoindentation results, the sample preheated at 300°C after annealing at 700°C exhibited an elastic modulus of 108.1?±?6?GPa and hardness of 5.97?±?0.3?GPa, which were almost 3% lower and 171% higher than the bare substrate, respectively.     

Adhesion of diamond coatings on steel and copper with a titanium interlayer

Adherent diamond coatings on steel and copper were obtained by using a titanium interlayer. The adhesion of the coatings was evaluated by scratch tests and micro-indentation tests. The diamond coating on steel exhibited a much higher critical load than on copper, as revealed by the scratch tests. However, an observation on the back of the scratch-delaminated film and on the corresponding substrate surface showed that the detachment occurred between the diamond film and the titanium interlayer. Therefore, the difference in the critical scratch load is due mainly to a substrate effect, making it difficult to compare the adhesion of different coatings.On the other hand, Knoop indentation tests showed interesting results: a small indentation load causes round spallation in the film with no observable crack. An exponential sink-in deformation under the indentation is proposed, y=−a exp(−bx). The coating adhesion is considered to be equivalent to the deformation stress at the edge of the spallation zone. The adhesion of diamond coatings on steel and copper with a titanium interlayer is evaluated quantitatively using this model. Furthermore, a thermal quench method is proposed to estimate the coating adhesion. The results found are in agreement with the indentation model.     

TC4合金表面Cu/micro-WC复合镀层和Cu/nano-WC复合镀层的性能

在TC4合金表面分别制备了Cu/micro-WC复合镀层和Cu/nano-WC复合镀层。比较了两种复合镀层的表面形貌、化学成分和显微硬度,同时分析了两种复合镀层的摩擦特性。结果表明:两种复合镀层都由Cu、W、C元素组成,显微硬度都明显低于TC4合金的显微硬度;摩擦试验前后,两种复合镀层表面轮廓曲线的形态都存在明显的不同;与Cu/micro-WC复合镀层相比,Cu/nano-WC复合镀层的表面形貌较好,W元素的质量分数较高,耐磨性较强。     

Investigation of the mechanical properties of electrodeposited nickel and magnetron sputtered chromium nitride coatings deposited on mild steel substrate

Electrodeposition and magnetron sputtering techniques have been employed for the deposition of Ni and bilayer NiCrN coatings, respectively, on mild steel substrate. Ni electrodeposition was performed using sulfate Watt’s bath, while magnetron sputtering was performed on electrodeposited Ni using DC power 350 W and base pressure of 3 × 10^?5 Torr in order to prepare bilayer NiCrN coatings. Structural and mechanical properties of Ni and bilayer NiCrN coatings have been investigated using various characterization techniques such as SEM-EDX, XRD, hardness, adhesion testing, etc. SEM analysis reflects the formation of spherical/nodular particles of varying sizes in NiCrN coating whereas Ni coating shows irregular, agglomerated, and non-uniform distribution of particles. Formation of hard CrN phase in NiCrN coating has been confirmed by XRD and EDX. NiCrN coating exhibits better hardness in comparison with Ni coating due to the formation of nitride phase. Micro scratch testing of bilayer NiCrN coating shows better interlayer adhesion and adhesion with mild steel substrate. The combination of electrodeposition and magnetron sputtering can produce inexpensive NiCrN coating containing hard CrN phase with better mechanical properties for automotive applications.