Chromium Coatings Research Articles

Enhanced solid particle erosion resistance of nanocrystalline Ni-W coatings through multilayer approach

Electrodeposited nanocrystalline Ni-W alloy coatings are projected as potential alternatives for hard chrome (HCr) coatings owing to their comparable hardness and superior corrosion resistance. However, the limited strain hardening ability of the nanocrystalline Ni-W coatings manifests in their poor resistance towards solid particle erosion involving a high strain-rate (>103 s−1) deformation. In the present study, a novel microstructural engineering strategy has been implemented to enhance the strain hardening ability of the nanocrystalline Ni-W coatings without compromising on their strength/hardness. Ni-W multilayer coatings composed of alternatively stacked soft (2.6 GPa) and hard (8.5 GPa) Ni-W layers were developed using the pulse reverse electrodeposition technique. Further, to investigate the effect of individual layer thickness (λ), multilayer coatings with different λ were deposited. Solid particle erosion testing using the angular SiO2 particles showed that the multilayer coatings (irrespective of λ) exhibit superior erosion resistance compared to the homogeneous nanocrystalline Ni-15W at both oblique (θ = 30°) and normal (θ = 90°) impact conditions. The post-erosion microstructural analysis of the multilayer coatings revealed that the hard Ni-W layers undergo uniform strain (ε > 50 %) without cracking due to the constrained co-deformation imposed by the surrounding soft Ni-W layers. Therefore, the enhanced erosion resistance of the multilayer coatings is attributed to the effective dissipation of impact energy through co-deformation of the individual hard and soft Ni-W layers.

Dry sliding wear behavior of hard-chrome and zinc-phosphate conversion coatings on steel substrates

We have studied tribological properties of conversion coatings, hard chrome on AISI 430 stainless steel, and zinc phosphate on AISI 1044 carbon steel. These substrates were chosen due to their extensive industrial applications. The goal of the present study is to improve the wear resistance of these substrates through the coatings. We performed nano-indentation and ball-on-disc tribometer experiments to study mechanical and tribological behavior of substrates and coatings. We find that when zinc-phosphate coating is applied to AISI 1044 steel, a new phase Zn2Fe(PO4)2·4H2O (phosphophyllite) is formed on the surface that increases the surface hardness. We further find that coefficient of friction decreases approximately by 8% due to hard-chrome coating on AISI 430 steel and by 48% due to zinc-phosphate coating on AISI 1044 steel under load and speed conditions applied in the present study. We attribute our findings to formation of: (1) an adhering layer of chromium in the case of chrome–steel contact, leading to chrome–chrome contact at the interface of test-specimen and counter-surface, and (2) a glossy layer at interface in the case of phosphate-steel contact, owing to the compaction and crushing of phosphate wear debris. Our wear studies show maximum reductions in specific wear rate to be around 80% and 89% for chrome and zinc-phosphate coatings, respectively. We note that adhesion and abrasion are the primary modes of wear for chrome and zinc-phosphate conversion coatings, respectively at the initial stage. However, adhesive wear switches to delamination wear at a later stage for hard-chrome coating.

A review on the environment friendly electroplating of Cr (III) & Cr (VI)

Chromium plating process is the most effective way of protecting the base material against hostile environment or improving surface properties of base material. There are several problems with traditional chrome plating. Traditional process uses toxic acid baths and may cause various health conditions. The baths employed contain chromic acid in which the chromium is in the hexavalent state. Hexavalent chromium has been proved to have toxic, mutagenic and cancerogenic effects for human health. As a result, In Europe, the implementation of the reach initiative will increase fees on companies still using Cr (VI) in 2017 and will require action plans to phase out Cr (VI) in the future. This has left the plating industry in a very delicate position with dark future prospects unless new solutions that are both effective and environmentally friendly are discovered. Superchrome Physical Vapor Deposition coating ahead of looming industry regulatory actions that will drive towards the removal of hazardous hexavalent chromium compounds. These new sputtered chromium coatings do not require a protective paint top coat to pass exterior automotive trim specifications. Visually the chromium coatings match those of electroplated decorative chromium in color and appearance.

CHROME PLATING OF PRESS TOOLING USED IN THE PRODUCTION OF NEW ELASTOMERIC MATERIALS

This research has produced multicomponent titanium-doped chromium coatings to strengthen the working surfaces of press tooling dies operated under aggressive conditions during the vulcanization of products from new elastomeric materials. The pressing was carried out on a hydraulic vulcanization press 100-400 2E. with plate sizes 400x400 of new elastomeric materials based on 10 wt.% carbonized fiber from PAN (RC Helper) or (USA), which significantly increases the heat capacity of rubber based on a copolymer of vinyl develfluoride and hexopropylene by 15-30% in the operating temperature range from 323 to 348 K. In the work, samples from mass-produced steels such as steel 20, steel 45, U8, 40H, and 40H16M were used for coating. Mixtures of powders with a dispersion of 60-250 microns of the following materials were used as reaction agents. In determining the required dispersion of reagents, we were guided by studies that found that the maximum completeness of the transformation is observed when using a reaction mixture with a fraction of 100-120 microns. The protective coatings on samples under the conditions of the SHS were obtained at the developed pilot plant DSTU12, consisting of the following main functional systems: reaction equipment; system for monitoring and controlling technological parameters; and gas utilization system. The organization of the SIS consists in creating a powder mixture and an environment that provides exothermic interaction at the local initiation of the process (ignition). Then, the reaction wave propagates spontaneously (combustion) and the synthesized product is cooled. According to the type of chemical reaction, three SWS processes can be distinguished: direct synthesis from elements; direct synthesis from compounds and exchange reactions; and metallothermal SHS (reactions with a reducing step). The surface microhardness of multicomponent chrome layers alloyed with titanium and boron is 20000 - 22000 MPa, which is due to the presence of the phase FeB. The microhardness of the alloyed Fe2В phase is 15000 – 16000 MPa. When chromium coatings are alloyed with titanium on the considered structural materials, the following phases are formed: (Fe,Cr)23C6, (Fe,Cr)7C3, Cr3C2, as well as phases: Fe2Ti, Cr2Ti. The surface microhardness of titanium-alloyed chromium coatings is: on steel 20 – H100= 16000 MPa, (phases: (Cr,Fe)23C6, (Cr,Fe)7C3, Fe2Ti, Cr2Ti, α- solid solution of Ti and Cr in α- iron), on steel 45 – H100 = 18000 MPa (phases: (Cr,Fe)23C6, alloyed with titanium, α-solid solution of chromium in iron with Cr2Ti inclusions), on U8 – H100= 19500 MPa (phases: directly on the outer side of the coating there is a zone of carbides (Fe,Cr)23C6, (Fe,Cr)7C3, Cr3C2, (Ti,Cr)C).

ЭЛЕКТРОХИМИЧЕСКОЕ ЛЕГИРОВАНИЕ ЦИНКОВЫХ ПОКРЫТИЙ ХРОМОМ И НИКЕЛЕМ ИЗ ГЛИЦИНАТНЫХ РАСТВОРОВ

The purpose of this work is the electrochemical alloying of zinc coatings with chromium and nickel from electrolytes containing heteronuclear complexes. Zinc coatings are widely used to protect steel products from corrosion in the atmosphere of various climatic zones. To increase corrosion resistance, zinc coatings are chromated or phosphated. An effective way to increase the corrosion resistance of the coatings under study is their alloying with other metals. Obtaining such coatings makes it possible to reduce their thickness and increase their service life, solve environmental problems when replacing cadmium. The kinetics of the process on zinc and steel electrodes has been studied by removing cathode polarization curves. It is suggested that the absence of characteristic current peaks on the polarization curves is due to the convergence of the electrode potentials of individual metal ions recovering from heteronuclear compounds, as well as the concomitant discharge reaction of proton donors. X-ray fluorescence analysis has shown that in the studied range of current densities 1-5 A/dm2, the content of alloying metals in the coating reaches 1.4% for chromium and 9.8% for nickel. The obtained data on the elemental composition of zinc coatings indicate an abnormal co-deposition of zinc with nickel. Chromium in coatings is observed at higher current densities of 4-5 A/dm2.The data obtained in this work can be used in electroplating in the development of processes for alloying zinc coatings with chromium and nickel in order to replace cadmium coatings.

Methods of structural surface engineering in solving problems of multifactorial improvement of materials performance

Problem. Structural surface engineering encompasses a complex of scientific disciplines and technological methods of directed change of physical and chemical properties of materials surface layers by modification, deformation, application of films, coatings, protective layers, with the help of various combined methods. In the course of the study several different methods of structural engineering of the surface are considered for solving problems of multifactor increase of the level of exploitation characteristics of materials. The methods described in the article are characterized by different physics of the process on the way to obtaining the result, but are aimed at modifying the structure and properties of the surfaces to which they are applied. Goal. Consideration of different methods of influence on the surface of ferrous and non-ferrous alloy objects, analysis of their influence on the modification of the structural state and properties of the surface layers that were investigated, discussion of the peculiarities of each of the considered technologies. Method. The first direction includes technologies that include a friction component, namely thermofriction treatment (TFT) for thermofriction hardening (TFH), supplementary thermofriction hardening (STH) or thermofriction welding (TFW). The second direction is the technology involving the use of anodic-cathodic electrolysis mode in alkali-silicate electrolyte – micro-arc oxidation (MAO). The third direction is the technology of vacuum-arc PVD-method, which involves obtaining chromium coatings. The article describes the features and results of application of such technologies, as well as the expediency of using this or that method for materials of different classes, schemes of the corresponding installations are presented. Results. The result of additional hardening of U8A steel surface from the microhardness level of 7.2 GPa to 14.7 GPa by DTFZ method after its thermal hardening practically to the maximum possible level is shown. The microstructure of the cross section of the pre-hardened U8A steel sample after DTFZ is presented, where the degree and character of surface hardening can be reliably seen. It is emphasized that in previous studies a consistently effective hardening of steels of various classes was achieved, up to a level of 22 GPa in 65G steel. The structure and properties of coatings on low-alloy aluminum alloys AB and AD1 formed in alkali-silicate electrolyte in the anodic-cathodic mode of MDO in the process of application of the microarc oxidation method have been studied. It is shown that the method of MDO in alkali-silicate electrolyte allows to obtain coatings with thickness up to 300 μm, coating growth rate ~ 2 μm/min and coating hardness 10-20 GPa. The coatings have high adhesion to the substrate, have a layered structure, the properties of the coatings are determined by the properties of the base layer. The coatings have a crystalline structure and consist of the following phases: γ-Al2O3, α-Al2O3, mullite (3Al2O3⋅2SiO2), the ratio between the phases depends on the electrolysis conditions. It is established that phase formation begins with the γ-Al2O3 phase, which in the process of further growth of the coating turns into the α-Al2O3 phase or interacts with silicon oxide to form the mullite phase. The possibility of obtaining high-quality chromium nitride-based hard coating by vacuum-arc sputtering is shown.

Development of Novel Coating on Metallic Bipolar Plates for Proton Exchange Membrane Water Electrolyzer Application

Considering the demand for a more environmentally friendly system, renewable and sustainable energy sources, such as wind and solar power are regarded as a promising substitute for fossil fuels in the generation of electricity. Since these energy sources exhibit intermittency and unpredictability, there is a need to develop a highly efficient and rapidly responsive energy conversion system for the purpose of storing this energy as a chemical fuel. Due to their ability to manage the variability of intermittent energy sources, proton exchange membrane electrolyzer cells (PEMECs) are garnering considerable interest. However, their broad commercial adoption is hindered by their relatively modest performance and elevated costs. PEM electrolysis is a promising technology for generating substantial quantities of hydrogen from surplus electricity generated by renewable sources. Nonetheless, the expense of the electrolyzer stack arises primarily from the metallic bipolar plates, because it possesses heavy weight and expensive precious metal coatings. Significant efforts have been performed on the development of titanium-based bipolar plates, but it has high base material and fabrication cost. In recent years, there has been a substantial focus on stainless steel bipolar plates for PEM electrolyzer application. Stainless steel can serve as an alternative, but it requires a coating to enhance its anti-corrosion properties. Electroplated chromium coatings exhibit favorable mechanical characteristics and find extensive application in precision mechanical components such as molds and surgical instruments. Their outstanding wear resistance, high hardness, impressive corrosion resistance, and glossy finish make them appropriate for many other applications, including both decorative and functional coatings. As a result, chromium electroplating has emerged as one of the most extensively employed techniques within the electroplating sector. The dense pack chromium layer is prepared on a 316L stainless steel substrate to enhance the anti-corrosion property and electronic conductivity.Herein, the role of gold striking underlayer, and thick chromium coating is studied for preparing the anti-corrosive stainless steel bipolar plates. First, a gold striking film as an underlayer on the stainless-steel substrate is electroplated to passivate the chromium-based oxides. Further, a thick and dense chromium layer is deposited on the gold underlayer by electroplating. The electroplating bath is operated using platinized titanium felt as an anode and 316L stainless steel as a working electrode without the separation of anodic and cathodic compartments. The electroplating solution is consisting of Cr (VI) oxide and H2SO4 (pH = 2). The nanocrystalline chromium coating with a thickness of approximately 2 µm is bright and uniform. Furthermore, gold as a protective layer of thickness approximately 1 µm is coated by electroplating on the chromium surface. The Cr and Au/Cr coatings are characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron microscopy (XPS) analysis. Subsequently, the protective layer-coated substrates were analyzed in a simulated PEM electrolyzer environment, and these coatings facilitated promising protective properties on the stainless-steel substrate. The corrosion testing was carried out in 0.5 M H2SO4 + 2 ppm HF solution at 70 0C purged with oxygen. The stable passive film and high corrosion resistance were obtained by gold striking underlayer and chromizing the 316L stainless steel substrate. As a result, the potentiodynamic polarization analysis showed the corrosion current density of 0.84 µA/cm2 for the Au/Cr-Au underlayer sample in a simulated operating environment. In contrast, the absence of the gold striking underlayer between Cr and stainless steel causes the pitting corrosion. The Au/Cr coating is tested in an acidic corrosion media for a long duration of 24 hours and it showed lower degradation as compared to without gold striking underlayer and without Cr film. The findings presented in this study illustrate the feasibility of employing stainless steel as the foundational material for the bipolar plate of a PEM electrolyzer.

Electrochemical Deposition in Vertical Tubes : An Hydrodynamic and Mass Transfer Study

The present work is part of the research project NXCHROME led by IRT M2P. It concerns the chemical engineering of metallic hard chromium coatings on internal surface of large tubular parts. These parts are intended to be used in several sectors of activity (aeronautics, armament, energy...). Thus, taking into account severe specifications related to these applications, the parts will be very strongly solicited thermomechanically during their use, which requested high performances to increase substrate's life. In the current process, tubes are treated vertically, by electrodeposition from a hexavalent chromium salt based (chromic acid) electrolyte. These electrolytes have the advantage of being efficient, easy to use, with well known functions. However, they have a low faradic yield (<20%), leading to an important production of bubbles (cathodic and anodic).These bubbles create the fluid motion, and eventually govern hydrodynamic, liquid flow and mass transfer of the species in the tube.It is important to note that the use of CrVI salts has been prohibited since 2017 (except for authorizations for applications without alternatives) by the European regulation REACh (Registration, Evaluation, Authorization and restriction of Chemicals). Indeed, hexavalent chromium is classified in Appendix XIV among SVHC (substances of very high concern), due to its high toxicity (CMR compound : Carcinogenic, Mutagenic and Reprotoxic) and the high danger it represents for coworkers using this compound. The objective of NXCHROME is to find a alternative process with a "REACh compatible" electrolyte based on an innovative trivalent chromium. The modus operandi and the electrochemical mechanisms involved are completely different and less well known, compared to the former electrolyte. Nevertheless, it keeps this low faradic yield and the liquid agitation mode in tubular parts will remains identical.Nevertheless, this change is a good opportunity for a deep investigation in the "bubble induced hydrodynamic" which occurs during plating time, and to collect all reliable information on fluids behavior. Then, two main research axis have been considered. The first one is done via the numerical simulation of the secondary current distribution, i.e. taking into account the electrical phenomena in the electrolyte (ohmic drop), the geometry of the system and the kinetics of the electrochemical reactions. This part is in collaboration with HIVELIX company. The second one trhought the design and elaboration of a large size experimental set-up in stainless steel and PMMA (φ = 40mm, L = 3000mm) Figure 1. This ste-up includes electrochemically active cathode parts (production of bubbles by hydrolysis), and transparent parts (windows of observations of the bubbles, according to the height of the tube). As it is the bubble production which puts in movement the fluid with their vertical displacement towards the surface, informations on their size and behavior are of primary importance. Their speed is determined by their size (depending on the distance covered and the coalescence) and the liquid physical properties.To mimic the chromium electrolyte, a transparent saline solution has been chosen and prepared by adjusting its parameters to be identical to the industrial electrolyte (viscosity, conductivity...), while allowing bubble production on the central electrode surface.Data collection and order of magnitude are done by various means, namely flow rate measurements, gas retention within the liquid and high frequency camera shots (bubble size, bubble velocity, coalescence...). Figure 1

Structure and Oxidation Behavior of a Chromium Coating on Zr Alloy Cladding Tubes Deposited by High-Speed Laser Cladding

Structure and Oxidation Behavior of a Chromium Coating on Zr Alloy Cladding Tubes Deposited by High-Speed Laser Cladding

Replacing Toxic Hard Chrome Coatings: Exploring the Tribocorrosion Behaviour of Electroless Nickel-Boron Coatings

Electroless nickel-boron coatings present outstanding properties such as high hardness, excellent wear resistance and uniform coating, and thus they are considered to be alternative to toxic hard chrome coatings. However, they contain lead that is toxic and used as stabilizer in the plating bath. This study aims to investigate the tribocorrosion behaviour of lead-free electroless nickel-boron coatings. In the present research, several tests were carried out to investigate the behaviour of these coatings under both dry and tribocorrosion reciprocating sliding wear against alumina balls, at room temperature. The open circuit potential (OCP) method was used to determine the degradation mechanism of the coatings. The results of the tribocorrosion and dry wear tests showed that the performance of coatings was very different from each other. A steady state for the coefficient of friction (COF) is achieved during the tribocorrosion test, whereas the constant production of debris and their presence in the contact implied an increase in COF with distance during the dry wear test. The wear mechanisms of these coatings also presented variations in these tests. It was found that the wear area calculated from tribocorrosion is lower (56 µm2) than the one from dry sliding test (86 µm2).

Hardness and tribological behaviour of annealed electroless nickel phosphorus composite layers with incorporated boron particles

In this study, a possible alternative to hard chromium coatings is investigated. Amorphous boron particles have been incorporated in electroless nickel‑phosphorus (NiP) deposits, yielding a dispersion coating. The distribution of the particles is homogenous and the maximum mass fraction of particles embedded in the coating is 6.2 ± 0.2 wt%. Measurements of the zeta potential and particle size of amorphous boron particles in a diluted electrolyte showed that the particles withstood agglomeration until 120 days. Primary and secondary hardness maxima are observed after thermal annealing at 400 °C and 860 °C due to the formation of nickel phosphide, nickel boride and nickel boride phosphide phases. X-ray diffractometry shows an increase in nickel and nickel phosphide crystal size at 400 °C before levelling off at 600 °C. The annealing duration should be kept between 30 and 60 min for optimal hardness. The wear resistance increases when the coating is annealed at 400 °C. DSC measurements on nickel phosphorus incorporated with boron particles, Ni-P-B, bulk material with P-content (9.6 ± 0,6 wt%) and B-content (4.5 ± 0.8 wt%) showed that the solidus line lies at 926 °C, which is why a maximum annealing temperature of 860 °C was chosen to avoid melting of the material. The relative texture and phase coefficients, RTC and RPC, showed that the nickel phase is preferred in the NiP system at 400 °C and 600 °C while the Ni3P phase is preferred in the Ni-P-B system at the same annealing temperature. REM and EDX area analyses are used to show the areal distribution of nickel, phosphorus, and boron before and after the annealing process along the thickness of the coating. A diffusion layer between substrate and coating that contains iron nickel boride and iron nickel phosphide lamellar structure is observed.

Advances in Corrosion Mitigation for Waste-to-Energy Systems: Evaluating Coatings and Application Techniques

Waste-to-Energy (WTE) systems, utilizing post-recycled municipal solid waste (MSW) and other biomass materials, are proven alternatives to landfilling for sustainable waste management. These processes offer benefits such as reduced landfill space, decreased methane emissions, and minimized waste volume. However, operational challenges, specifically high-temperature corrosion (HTC) of superheater tubes, hinder their efficiency due to the presence of chlorine, alkaline salts, and sulfates. To address this issue, a range of coating techniques have been developed, with thermal spray techniques, particularly high velocity oxy-fuel (HVOF) spray, proving the most effective for protecting superheater tubes. A comparative analysis of experimental data from multiple studies indicates that coatings with Alloy 625, Alloy C-276, Colmonoy 88, FeCr, IN625, NiCr, NiCrTi, and A625 offer high corrosion resistance at relatively low material costs, with corrosion rates below 1 mm/year. High chromium, nickel, and molybdenum content coatings perform exceptionally well under high-temperature and high-chlorine conditions. Notably, T92 and P91, due to their low cost and high corrosion resistance, are strong candidates for superheater tubes operating at 550°C. While A625 demonstrates excellent corrosion resistance, its high cost limits its practicality. Ultimately, the selection of suitable coatings depends on the specific WTE plant design and operating experience. The additional cost of applying these coatings is a minor fraction of the overall financial gains, as it extends the superheater tubes' lifetime and reduces plant downtime for tube repair or replacement.

Influence of Doped Detonation Nanodiamonds on the Physical and Chemical Properties of Electrochemical Chromium Coatings

Chromium deposition process regularities are analyzed in the standard chromium plating electrolytes, with and without detonation nanodiamonds additives modified with boron, phosphorus (DND-boron, phosphorus-DND) at a temperature of 50º to 55ºC while stirring the solution and without. It was studied by method of recording the partial polarization curves the concentration effect of additives DND-boron (in the range of 2,5 ÷ 10 g/l) on the kinetics of the chromate ion partial and full reducing. It has been shown that increasing the concentration of DND-boron leads to inhibition of the reaction Cr (VI) → Cr (III) and Cr polarization curves shift reaction (VI) → Cr (0) to a negative potential on the magnitude of 40-70 mV. While stirring the electrolyte chromium deposition occurs at more positive potentials than in quiescent electrolyte. Dependence of the electrode potential on the current density logarithm in all cases are linear with a slope close to 120 mV, indicating a limiting step of attaching the first electron. Mechanism of deposition of chrome in the presence of boron-DND does not change. Shiny, smooth, uniform coatings are deposited in electrolytes with DND-boron additives. Increased polarization in the chromium precipitation of electrolytes with DND-boron causes a change in precipitation structure, and as a consequence an increase in microhardness of chrome coatings from 955 kgf/mm2 for pure chromium to 1430 kgf/mm2 for chromium with embedded DND-boron nanodiamond particles. Wear resistance is increased: using DND-TAN - 2-3 times compared to standard chrome plating, using DND-phosphorus - in 3 times in comparison with DND-TAN, and using DCS (Si), doped silicon, wear is not detected (under the test conditions).

Passivation of the HAYNES® 214® Nickel-Based Superalloy via Pulsed Laser Deposition of Alumina and Chromia Coatings for Enhanced Corrosion Resistance at Intermediate Temperatures

Passivation of the HAYNES® 214® Nickel-Based Superalloy via Pulsed Laser Deposition of Alumina and Chromia Coatings for Enhanced Corrosion Resistance at Intermediate Temperatures

Synthesis, Characterization of Chromium Oxide Powders and Coatings

The chromium oxide powders are transformed into plasma sprayable particles by using synthetic polymers for agglomeration. In order to carry out the agglomeration process, spray drying technique was employed. This research work highlights the significance of the process variables that control the synthesis of plasma spray powder and consequently, the properties that were suited for plasma spray coating. Energy Dispersive Spectroscopy (EDS) was used to characterize the elemental composition, while scanning electron microscopy (SEM) was used to analyse the morphology and powder grain sizes and X-ray diffraction (XRD) was used to identify the phase structure. And for the development of coatings on the substrates, Atmospheric plasma spray (APS) technique was used. The plasma sprayable powders were created with the intention of investigating for use as corrosion-resistant coatings.

Chromium Coating of Wollastonite Filled Polyamide 6 and Evaluation of Thermal Cycle Strength

The chromium coating of plastic/polymer materials through electrolysis method has attracted attention for improving material properties. The most common material used to be coated is the Acrylonitrile Butadiene Styrene (ABS), but has disadvantages compared to polyamides (PA), such as low thermal resistance. PA’s high water retention disadvantage can be substituted by using fillers such as clay, etc; so in this study, 40% Wollastonite filled PA has been used for chromium plating to increase the thermal resistance of the PA. The plates used were produced by injection molding method. The research is focused on the effect of time and concentration on coating performance in etching, activation (by palladium) and accelerator processes. SEM and EDX were used to characterize samples for surface morphologies and the microstructures of etching, activation and accelerator in the PA sub-plates. Additionally, cross-cut adhesion test has been applied to analyze the adhesion power of the interfaces. It was found that the thermal resistance of the metal plate on the polymer surface decreased as the time increased, in relation with the increasing wearing time of the metal plate mentioned above. The thermal resistance decreased as the polymer deformed in relation with the increase in etching solution’s concentration. It is also seen that the thermal resistance improved as the activation time increased. The adhesion and the thermal resistance did not improve as the time in accelerator process increased. Furthermore, the cross – cut adhesion tests on the same samples concluded that the results are in agreement with the other thermal resistance results.

Mechanical and Morphological Characteristics of Nickel, Chromium and Nitride-Based Coatings Formed via Electrodeposition and Magnetron Sputtering Techniques on Mild Steel. An Overview

Mild Steel (MS) is considered as the most widely employed engineering material, which is primarily being used in an automotive industry. Several parts including fuel system, outer and body panel, trims, chassis exhaust, along with many other parts are made up of MS. The driving force behind versatility of MS is its unique set of characteristics. However, the issues arise when its tribological degradation occur that creating problems in service conditions. The best solution for this problem is to coat the mild steel with transition metal-based nitride coatings such as, Ni and Cr. Insufficient Literature is available related to the mechanical performance of single/gradient layer (Ni, Cr) N ternary coating on mild steel substrate. Current review focuses on the characteristics of the coatings that are deposited through two different deposition techniques; electrodeposition and magnetron sputtering. The studied coatings materials are nitrides of nickel and chromium, deposited in several layers. Furthermore, the structural and mechanical properties of these coatings have been compared.

Studies of adhesive and wear-resistant properties of chrome coatings for car parts and road construction equipment restoration

Introduction. The use of chrome plating as a method of restoring parts that work with waterjet wear is important for restoring the operability of hydraulic drive units and parts used in specialized vehicles and road construction equipment. The proposed method of chrome recovery has the necessary advantages, it is a sufficiently high performance and microhardness of the resulting chrome coatings. However, for implementation in production, additional studies of the reliability of the chrome coatings obtained, namely, adhesion strength and wear resistance, were required. This will make possible to draw conclusions about the prospects for further implementation and use for the restoration of hydraulic drive parts and other parts that work with waterjet wear.Materials and methods. To conduct the research, equipment meeting the requirements of technical conditions, using existing and developed devices and devices for obtaining chrome precipitation was used. For this purpose, the necessary devices and samples from the appropriate material to approximate the reliability of the obtained research results were made. Also the necessary improvements to digitize the data obtained on the friction machine were made.Results. The performed studies of adhesion strength have shown that the chrome coatings obtained from the new electrolyte composition will make possible to obtain adhesion strength reaching 270 MPa, which is sufficient for parts operating at high pressures (20 MPa) with the necessary margin of safety. Also the studies conducted on the wear resistance of chrome coatings let to conclude that the wear resistance of the chrome coatings obtained is 20-30% higher compared to the reference surface (the material of the spool manufacture).Discussion and conclusion. The studies of the obtained chrome coatings from the new electrolyte composition made possible to establish, which let to establish the regularities of the influence of the electrolyte composition and the modes of testing the wear resistance of the precipitation obtained compared with the existing universal chromium plating electrolyte. The results obtained confirmed the possibility of using a chrome coating from a new chromium plating electrolyte for the restoration of car parts and road construction machines operating under waterjet wear.

Preparation and Research of Chromium Coatings with Diamond Nanoparticles Deposited Directly on a Monolithic Composite of Niobium and Aluminum

Preparation and Research of Chromium Coatings with Diamond Nanoparticles Deposited Directly on a Monolithic Composite of Niobium and Aluminum

Low-density HiPIMS favored ultrathick and compact chromium coatings on Zircaloy-4 alloys

Protective metallic coatings are receiving increasing attention to modify the anti-corrosion and oxidation resistance of zirconium-based fuel cladding tubes under harsh high-temperature steam/air oxidation conditions. In this work, ultrathick (∼20 μm) and compact Cr coatings with (001) preferential orientation were deposited on Zircaloy-4 (Zry-4) alloy by high power impulse magnetron sputtering (HiPIMS) technique. The growth characteristics of the Cr coatings were investigated as a function of the discharge plasma species, including Cr+, Cr*, Ar+, and Ar*, which were controlled by the different discharge modes during HiPIMS process. The results showed that, when the discharge feature was changed from the ‘low voltage direct current magnetron sputtering (DCMS)-like’ mode into a ‘low density HiPIMS’ mode, a rapid increase of Cr+ content in the substrate vicinity was obtained by time-integral optical emission spectra (OES), indicating a remarkably enhanced incident energy flux to the deposited Cr coating. The generalized temperature increment of the Cr coating growing surface calculated from the OES, was ∼100 K and was mainly affected by the incidence of Cr* atoms. A simplified collision model based on the non-penetrating ions/atoms assumption was also proposed to calculate the transferred energy from the incident energetic species and thus understand the predominant effect of HiPIMS Cr plasma on the achieved nanocrystalline Cr coating with ultra-thick and dense structure, which is still quite challenging for the DCMS deposition process.