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To reduce the corrosion degradation of copper alloys, an equiatomic CoCrNi medium-entropy alloy (MEA) coating was successfully fabricated on a copper alloy plate using high-velocity oxygen-fuel (HVOF) spraying. The microstructure, corrosion behaviour, and passive film characteristics of the CoCrNi MEA coating in a 3.5 wt.% NaCl solution were investigated. The CoCrNi MEA coating mainly consisted of a face-centred cubic solid solution structure and a small amount of metal oxide. Compared to that of the widely used electroplated NiCo coating, the corrosion current density of the CoCrNi MEA coating dropped by 93%. The pitting corrosion of the CoCrNi MEA coating originated from the interface between the solid solution matrix and the oxide. Due to the strong protective passive film and low coincident site lattice boundaries, the CoCrNi MEA coating exhibited superior corrosion resistance in a NaCl solution. [ABSTRACT FROM AUTHOR]

Bacterial biofilms on foreign surfaces are considered a primary cause of implant-related infections, which are challenging to treat. A new implant coating was developed, containing anti-infective silver within a biocompatible polymer carrier substance. In addition to its passive effect on the implant surface, highly concentrated anti-infective silver can be released as needed via the application of high-energy shock waves. This intervention could be applied transcutaneously in a clinical setting without the need for additional surgery. We investigated the inhibition of biofilm formation and the effectiveness of eradication after activation of the coating via shock waves in an in vitro biofilm model using Staphylococcus epidermidis RP62A. This was performed via scanning electron microscopy and quantitative microbiology. Additionally, we examined the cytotoxicity of the new coating on normal human fibroblasts and Saos-2 osteoblast-like cells, depending on the silver concentration. All studies were compared to uncoated titanium surfaces Ti6Al4V and a conventional electroplated silver coating. Cytotoxicity toward normal human fibroblasts and Saos-2 osteoblast-like cells increased with higher silver content but remained tolerable at 6%. Compared to uncoated Ti6Al4V and the electroplated silver coating, the new coating with a silver content of 4% and 6% exhibited a significant reduction in adherent bacteria by a factor of approximately 1000. This was also evident via microscopic examination of the surface morphology of the biofilms. Furthermore, following shock wave activation, no bacteria were detectable on either the implant or in the surrounding fluid after a 24 h period. [ABSTRACT FROM AUTHOR]

Implant-related infections are a significant concern in orthopedic surgery. A novel anti-infective implant coating made of bioresorbable polymer with silver nitrate was developed. A controlled release of silver ions into the vicinity of the prosthesis can be triggered on-demand by extracorporeal shock waves to effectively combat all clinically relevant microorganisms. Microscopy techniques were used to examine the effects of shock wave application on coated titanium discs. Cytotoxicity was measured using a fibroblast proliferation assay. The anti-infective effect was assessed by monitoring the growth curves of three bacterial strains and by conventional culture. Microscopic analysis confirmed surface disruption of the coatings, with a complete release of silver in the focus area after shock wave application. Spectrometry detected an increase in silver concentration in the surrounding of the discs that surpassed the minimum inhibitory concentration (MIC) for both S. epidermidis RP62A and E. coli ATCC 25922. The released silver demonstrated an anti-infective effect, significantly inhibiting bacterial growth, especially at 6% and 8% silver concentrations. Cytotoxicity testing showed decreasing fibroblast viability with increasing silver concentration in the coating, with 6% silver maintaining viability above 25%. Compared to a commonly used electroplated silver coating on the market, the new coating demonstrated superior antimicrobial efficacy and lower cytotoxicity. [ABSTRACT FROM AUTHOR]

This work deals with the development of cyanide-free copper-silver electroplated coatings on AISI-1075 steel and its corrosion behavior under a 5% NaClO solution (commercial household bleach). A cyanide-free bath based on sodium thiosulfate was employed to obtain the silver coatings using current densities from 0.2 to 5.0 mA/cm2 and different concentrations of EDTA (additive). The evolution of the open circuit potential with time showed that silver is anodic with respect to copper, so there were no intense attacks in the silver pores. Adhesion measurements were made on both coatings by the tape test. The behavior against corrosion was evaluated by polarization resistance (Rp) in samples with the best coating adhesion. The best results were obtained with a silver coating of about 20 μm in thickness deposited on copper coating previously polished with colloidal silica. The best performance was attributed to the formation of AgCl as demonstrated by x-ray diffraction and scanning electron microscopy. [ABSTRACT FROM AUTHOR]

Herein, the effect of heat treatment on the high‐temperature wear resistance of Ni–Co electroplating coating on copper surface is systematically investigated. Results show that the oxide layer formed on the surface of coating during heat treatment induces the wear mechanism transition of coating. Under the condition without oxide layer formation (heat treatment at 400 °C), the coating suffers severe adhesive wear due to the low hardness caused by grain growth. After heat treatment at 600 °C, the formation of CoO and Co3O4 oxide layers on the surface of coating improves wear resistance, and the wear mechanism changes to oxidative wear and adhesive wear. The density of the oxide layer determines the degree of adhesive wear. As the heat treatment temperature increases (900 °C), the formation of a denser NiCo2O4 oxide layer with higher hardness further inhibits the adhesive wear mechanism of the coating. Until more than 6 h, the formation of scale‐shaped NiCo2O4 and 3CoO·NiO oxide layers significantly improves the wear resistance of the coating and completely eliminates adhesive wear. The wear mechanism is transformed into oxidative wear. [ABSTRACT FROM AUTHOR]

The choice of the electroplating conditions of Ni-based alloys has always been a serious research question. In this study, an artificial neural network based on central composite design modelization were used to determine the desired percentage of Ni and the optimum thickness of the coating before passing to the implementation of the work. Three main factors were found to be very important in this process; namely applied current density (I), pH of the bath and the temperature (T) during electrolysis. The optimum conditions generated by the mathematical model proposed in this work were 42 mA cm−2, pH 4.5 and 50 °C for the Ni-alloys (Zn, Co, Cr and W). Theoretically, the optimum amount of Ni and the thickness of the alloy were 40% and 23 µm, respectively. The SEM images indicated that the optimum (I) would yield homogenous and compact morphologies. Moreover, the XPS investigations revealed that the optimum pH would form a strong Ni bond. Finally, the XRD analysis showed that the optimum T would result in a stable Ni-alloy crystallinity for Zn, Co and Cr. In contrast, Ni-W alloys showed that the amorphous phases were more stable. [ABSTRACT FROM AUTHOR]

Quantitative characterization of tensile stress in electroplated nickel coatings on the copper substrate with the thickness range of 2.809 µm to 35.654 µm in the elastic stage was experimentally performed with a magnetic incremental permeability (MIP) sensor in the study. Firstly, a differential mutual-inductance sensor based on the parallel excitation of bifilar co-directional coil was proposed. With the proposed sensor, multiple signals including high-frequency eddy current (HFEC), tangential magnetic field strength, and magnetic incremental permeability butterfly curve (MIPBC) could be measured synchronously and eight typical magnetic parameters were obtained from experimental signals. Then, four parameters including the peak height of MIPBC, amplitude at cross point of MIPBC, difference frequency of HFEC, and sum frequency component of HFEC were selected to quantitatively characterize tensile stress. Experimental results showed that the four parameters depended on tensile stress and showed a parabolic trend. The parameters of the parabolic equation varied with nickel coating thickness. Finally, a polynomial surface fitting method based on the combination of the factors of thickness and tensile stress were derived with the selected four parameters and the coefficient of determination R 2 was higher than 0.9. The further comparison between theoretical results and predicted stress confirmed that the proposed MIP sensor could realize the quantitative detection of tensile stress in different nickel coatings. [Display omitted] • A multi-functional MIP sensor, with the ability of several magnetic signal measurement, was developed. • The multi-functional MIP sensor not only suppresses mutual inductance signals, but also provides compact structure. • MIP sensor accurately predicts tensile stress in electroplated nickel specimen, accounting for variations in specimen thickness. [ABSTRACT FROM AUTHOR]

A new strategy for preparing TaC coatings on easily oxidized tantalum by non-vacuum carburizing is proposed, which is called Fe-coating-mediated carburization. Fe-coating-mediated carburization is the carburization of Ta substrate with a pre-electroplated Fe coating. During carburization, the electroplated Fe coating was transformed into a carbon steel coating, while a high concentration of interstitial carbon atoms in the carbon steel coating diffused into tantalum, forming a TaC coating. The Fe coating isolated the tantalum from oxygen and changed the state of active carbon atoms in contact with the tantalum surface. The TaC coatings are nonporous, have fine grains with grain size gradients, and combine high hardness (32 GPa) and excellent coating-substrate adhesion strength (>100 N). The Fe-coating-mediated carburization realizes the carburization of oxidizable carbide-forming metals under non-vacuum conditions, providing a new strategy to prepare protective coatings with both high hardness and high coating-substrate adhesion for carbide-forming metals. • A surface hardening method called Fe-coating-mediated carburization is proposed. • Non-vacuum carburization of easily oxidized tantalum is realized. • The coating is nonporous and has a gradient microstructure with fine TaC grains. • The hardness reaches 32 GPa and the adhesion strength exceeds 100 N. • The function of the Fe coating and the advantages of this method are elucidated. [ABSTRACT FROM AUTHOR]

The failure behavior of electroplated Cr coating on the surface of PCrNi3MoVA steel was studied under the combined thermal and mechanical action. The microstructure and crystal phases of electroplated Cr coating at different failure stages were analyzed by SEM, EDS and XRD. It is found the brass friction pair material will melt and penetrate into Cr coating along the crack direction at high temperature, which can accelerate or slow down the failure process of Cr coating depending on the location. At the same time, the results show that the temperature variation is the main factor leading to the internal crack of the coating, the peeling of the coating and the growth of the oxide of the steel substrate. The mechanical friction is the main factor leading to the surface fragmentation and the internal delamination peeled of the coating. • Failure analysis of Cr coatings by comparative test • The thermal - mechanical coupling damage experiment is carried out • H90 brass is introduced as the friction pair material of friction test • Oxide development morphology between 800 °C and 900 °C is obviously different • Effect of brass penetrate into different positions of Cr coating on failure process [ABSTRACT FROM AUTHOR]

• Comprehensive market survey on commercially-available absorber coatings. • Modelling of the efficiency parameters with a validated steady-state collector model. • Simulation of the thermal system performance of different collector absorbers. • Analysis of the impact of the optical properties on the stagnation behavior. We present a comparative simulative study to evaluate the efficiency and stagnation behavior of commercially available absorber coatings for solar thermal flat-plate collectors. A market survey has revealed different absorber coatings, which exhibit solar absorptances of α > 90% and thermal emittances ε of 5–90%. All these coatings can be classified as wet-chemically electroplated coatings on the basis of black chrome, highly selective sputtered PVD coatings, solar paints and novel thermochromic coatings. We calculated the annual solar collector energy output by means of collector simulations with the tool ScenoCalc and compared the collector efficiency of several absorber coatings. We have carried out TRNSYS simulations both with systems for solar domestic hot water preparation and solar-assisted space heating. In a solar domestic hot water system with a daily tapping volume of 100 L we report an increase in the auxiliary energy demand of up to 6% with black chrome, 7% with thermochromic and 21% with solar paint coatings compared to sputtered PVD coatings. In a solar combisystem the increase in the auxiliary energy demand does not exceed 1.4% for thermochromic and black chrome coatings and 6.1% for solar paints. The stagnation period can be reduced from 178 h per year (PVD coatings) to 118 h, 62 h and 11 h for black chrome, thermochromic and solar paint coatings, respectively. The maximum absorber temperatures decrease from 175 °C (PVD coatings) to 165 °C for black chrome, 145 °C for thermochromic and 135 °C for solar paint coatings. [ABSTRACT FROM AUTHOR]

The microstructure, microhardness and wear property of electroplated Ni–ZrO2 nanocomposite coatings with different ZrO2 concentration were analyzed using SEM, microhardness and wear tests. It was found that in the composite coatings, incorporation of ZrO2 particles improves the mechanical property of Ni coatings and the effect of ZrO2 nanoparticles concentration on the surface morphology, microstructure and mechanical property of electroplated coatings was discussed. The mechanical properties of Ni–ZrO2 coatings reach the optimum value when the ZrO2 concentration is 10 g/L. [ABSTRACT FROM AUTHOR]

Since the inception of Nickel electrodeposition coating by G. Bird in 1837, it has been the area under discussion of research. From the past several decades, prominence has shifted for its exclusive applications and properties in the field of engineering. It has several advantages as compared to conventional electrolyte coating. Due to excellent tribological properties the electroplated nickel coatings are widely used in chemical, automobile, aerospace, and electrical industries. To enhance these properties of electrodeposition of nickel coating the researchers have introduced second phase particles such as SiC, ZrO2, B4C, TiO2, Al2O3, Si3N4, CeO2 etc. These researchers have shown that theses second phase particles will result in the improvement of tribological characteristics. Industries demand new coating materials with enhanced tribological characteristics for its applications. The present article review the tribological advantages of different electrodeposited nickel coatings based on the bath types and structure. [ABSTRACT FROM AUTHOR]

The process of electrical discharge coating (EDC) may be used to deposit hard materials on conformal substrate surfaces. Next generation EDM'd components may exploit attachment phenomena to enhance recast layer properties, to avoid the need for recast layer removal. Here, a ceramic based composite layer was developed without cracking and porosity for the first time, using sequential coating using sacrificial TiC and Si electrodes. Attenuation of the discharge process by gap widening using Si debris in the gap explained improved layer properties. Composite coatings combining WC and TiC were also demonstrated, with good elemental intermixing. Attachment level was correlated strongly with melting point, with high melting point materials resisting ejection due to more rapid solidification. Nanoindentation showed the TiC and WC/TiC layers possessed the highest mean hardness values, approximately double that of the Cu based machined layer which itself yielded a much higher hardness of 11.0 GPa compared to 1.9 GPa of the substrate. [ABSTRACT FROM AUTHOR]

In this paper, we propose a method to deal with the control of an electroplating line without stopping the production. The considered system is running in repetitive functioning mode, and it is modelled by a P-time event graph. The main objective is to switch the number of parallel resources to maintain a resource while the production is assumed to be always running. So, two functioning modes appears: normal and maintenance modes. Each mode is described by a state space model written in the standard algebra and a global model corresponding to a switching system which is a class of hybrid systems is obtained. Using model predictive control technique, stabilizing state feedback gains are computed over an infinite horizon respecting the time constraints while maintenance is performed. [ABSTRACT FROM AUTHOR]

Co-plating of Cu-Ni coatings by supercritical CO2 (sc-CO2) and conventional electroplating processes was studied in this work. 1,4-butynediol was chosen as the surfactant and the effects of adjusting the surfactant content were described. Although the sc-CO2 process displayed lower current efficiency, it effectively removed excess hydrogen that causes defects on the coating surface, refined grain size, reduced surface roughness, and increased electrochemical resistance. Surface roughness of coatings fabricated by the sc-CO2 process was reduced by an average of 10%, and a maximum of 55%, compared to conventional process at different fabrication parameters. Cu-Ni coatings produced by the sc-CO2 process displayed increased corrosion potential of ~0.05 V over Cu-Ni coatings produced by the conventional process, and 0.175 V over pure Cu coatings produced by the conventional process. For coatings ~10μm thick, internal stress developed from the sc-CO2 process were ~20 MPa lower than conventional process. Finally, the preferred crystal orientation of the fabricated coatings remained in the (111) direction regardless of the process used or surfactant content. [ABSTRACT FROM AUTHOR]

The effects of grain refinement and enhancement in the micro-mechanical strength were observed in the Au film fabricated by electroplating with a supercritical CO 2 contained electrolyte (EP-SCE). The ultra-fine grained Au film was achieved when a current density of 5 mA/cm 2 and a pressure of 10 MPa were applied. High carbon content was also observed in the film, which contributed to the grain refinement effect and expected to stabilize the ultra-fine grain structure. Micro-mechanical properties of the Au films were evaluated by micro-compression tests for the applications as the components in micro-electronic devices. Dimensions of the fabricated Au micro-pillar were 10 × 10 × 20 μm 3 . The 0.2% yield strength and the compressive flow stress of the Au micro-pillar reached 520 MPa and 800 MPa, respectively. The micro-pillar fabricated from the EP-SCE Au film exhibited a much higher mechanical strength than that from the conventional electroplated Au film. [ABSTRACT FROM AUTHOR]

Specific features of preparation of paint-and-varnish nickel-polymer coatings by joint cathodic electrodeposition of an amine-containing oligomeric electrolyte and nickel were studied. The coatings obtained exhibit layer-by-layer heterogeneity, with the lowest layer constituted by an intermetallic compound of nickel with iron. The coatings are characterized by higher degree of cross-linking compared to the polymer coatings without nickel. A paint-and-varnish formulation based on a nickel-polymer film-forming agent was developed for electrodeposition of corrosion- and wear-resistant coatings. [ABSTRACT FROM AUTHOR]

Tin whiskers are filamentary growths that are formed on the surface of electrodeposited tin, which is used extensively in the electronics industry. The presence of whiskers on electroplated finishes has been observed for more than 60 years, but, despite a huge amount of work in this area, a definite mechanism by which whiskers grow remains unidentified. Whiskers pose a significant problem for manufacturers of electrical and electronic equipment, since they are able to grow across and bridge the gap between adjacent electrical components, resulting in short-circuits and other associated failures. For many years, whisker growth was effectively mitigated by the addition of lead to tin electrodeposits. However, recent legislation prohibits the use of lead in new electrical and electronic devices, and thus alternative whisker reduction techniques are being sought. Effective mitigation is critical in ensuring that widespread whisker initiated failures can be avoided. However, since the mechanism, or mechanisms, which cause whisker growth remain unknown, the development of effective mitigation techniques is a significant industrial challenge, but a challenge which must be undertaken. This review examines some of the work undertaken to elucidate the whisker growth phenomenon. A brief history of whisker initiated failures along with key developments in whisker theory is presented. This is followed by a more detailed assessment of the several growth mechanisms hypothesised; dislocation-based, recrystallisation-based and compressive stress-based theories. The structure and properties of tin whiskers, along with factors that affect whisker growth and potential mitigation techniques are discussed. [ABSTRACT FROM AUTHOR]

Ni/NiFe 2 dual layer coating is fabricated to improve the performance of SUS 430 steel as solid oxide fuel cells (SOFCs) interconnects by a combined approach. Ni layer is deposited by electroplating or magnetron sputtering, and subsequently the NiFe 2 layer is sputtered on it. The coated steels are evaluated at 800 °C in air corresponding to SOFC cathode environment. It is found that the coating with electroplated Ni and sputtered NiFe 2 results in breakaway oxidation after 5 weeks. Preoxidation treatment in 900 °C air for electroplated Ni steel prior to depositing NiFe 2 layer improves oxidation resistance. The sputtered Ni and NiFe 2 sample exhibits superior oxidation resistance and inhibition against Cr outward migration while maintaining a low area-specific resistance (ASR) of surface scale. Comparative analyses of the coating preparation and resultant oxidation behavior with possible mechanisms and implications are discussed. • Ni layer is electroplated and sputtered to prepare Ni/NiFe 2 dual layer coating. • Cr out-migration was effectively prevented by the converted oxide coating. • Electroplating Ni reduced oxidation resistance while sputtering Ni enhanced it. • Surface scale of sputtered Ni sample exhibited a better electrical conductivity. [ABSTRACT FROM AUTHOR]

Aiming to improve the protection of human health and the environment, REACH regulation was enforced across European Union, accelerating the need to find alternative solutions to the electrodeposition processes of hexavalent chromium employed in several industrial applications. Electroplated chromium coatings are widely used due to their physical and mechanical properties that allow a longer service life of products that usually fail due to wear. Minting is one of those applications where good mechanical and tribological properties are required and where hard chromium has an important usage without being outmatched by other coatings. This study presents the development of an alternative coating to hard chromium with outstanding mechanical properties, in particular high resistance to cyclic loads. Cr(Al , Si)N coatings have been produced by reactive DC magnetron sputtering. Focusing on mechanical properties, an increase in the hardness was observed with the consecutive addition of elements to the base matrix (CrN), ranging from ≈10 GPa in CrN coatings up to ≈17 GPa for the CrAlSiN coatings. In nano-impact tests, CrAlN coatings had the best performance and no crack events by fatigue were observed by SEM after 50 impacts, with load maximum 20mN, with an estimated maximum contact pressure of 1.5 GPa much higher than the one requested for coinage. The fatigue wear was governed by the H/E ratio and plasticity index showing that Cr(Al , Si)N coatings deposited by reactive magnetron sputtering can be considered excellent candidates for cyclic loading, as in minting applications. • In nano-impact tests, CrAlN coatings withstood 1.5 GPa without failure. • Depth of initial indentation after 50 impacts was lower in CrAlN than in steel. • Cr(Al , Si)N coatings are viable alternatives to hard chromium under cyclic loads. [ABSTRACT FROM AUTHOR]

In this paper we study the influence of the roughness of the copper substrate on the magnetic properties of the FeNi film we electroplate onto it. The roughness and the thickness of the copper substrate are reduced by electropolishing in orthophosphoric acid: we show how to select the working point, which gives the highest smoothness, avoiding defects due to gas evolution. Finally we show how a smoother substrate contributes to reducing the coercivity of the magnetic film grown on it. [ABSTRACT FROM AUTHOR]