Effects of Hard Surface Grinding and Activation on Electroless-Nickel Plating on Cast Aluminium Alloy Substrates (original) (raw)
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2018
The purpose of this investigation is to explore the relationship between various zincating treatments and coating adhesion. A modification on the conventional single zincating process has been made by extending the duration, with an objective to enhance the non-homogeneous deposition of zinc particles on the aluminium alloy 7075 (AA7075) substrate. To compare the impact of various zincating treatments on the coating adhesion, a double zincating process at various durations were also applied in this study. A scanning electron microscopy (SEM), atomic force microscopy (AFM) and energy dispersive analysis of x-rays (EDX) were used to characterize the microstructural changes and composition of AA7075 during various zincating treatments at various durations. A scratch tester was used to investigate the coating adhesion of nickel deposits. A strong relationship between zincating duration and surface morphology of the zincated substrate has been observed in SEM results. The adhesion betwee...
Study of Electrochemical Polishing Applications in Some Alloys for High Surface Finish
Electrochemical polishing with 10% Sodium chlorate electrolyte was used to investigate chemical polishing for three metal alloys used widely in mechanical industries, to obtain high surface finish. The relationships between polishing time – surface roughness, and current density – surface roughness were studied for hot work tool steel, cold work tool steel and dure aluminum. Form which it has been shown that it was possible to obtain surface roughness (2.8μm)for hot work ,(2.5), (2.31 μm), for cold work tool steel and dure aluminum respectively. This study was applied in Nasser state company for mechanical industries / central tool plant to obtain high quality polishing for injection mould cavity, blow mould, spure gear, bevel gear and combustion chamber parts.
Journal of Metallurgy, 2015
The effects of temperature, pH, and time variations on the protective amount and quality of electroless nickel (EN) deposition on cast aluminium alloy (CAA) substrates were studied. The temperature, pH, and plating time were varied while the surface condition of the substrate was kept constant in acid or alkaline bath. Within solution pH of 5.0–5.5 range, the best quality is obtained in acid solution pH of 5.2. At lower pH (5.0–5.1), good adhesion characterised the EN deposition. Within the range of plating solution pH of 7.0 to 11.5, the highest quantity and quality of EN deposition are obtained on CAA substrate in solution pH of 10.5. It is characterised with few pores and discontinuous metallic EN film. The quantity of EN deposition is time dependent, whereas the adhesion and brightness are not time controlled. The best fit models were developed from the trends of result data obtained from the experiments. The surface morphologies and the chemical composition of the coating were ...
HAL (Le Centre pour la Communication Scientifique Directe), 2019
Aluminium and its alloys have a great potential for application in aerospace and automotive industries because of low cost, lightweight and good strength. Depositing hard coatings on Al alloys substrate is often used to improve the poor Al wear resistance. In this study, the way to improve the mechanical behaviour of Al alloys is to deposit a nickel layer followed by a heat treatment. Al-5%Mg alloy samples were electroplated using pure nickel. The deposition was carried out in a stirred standard nickel-plating Watts bath, with a current density of 2 A.dm-2 , a pH of 4.2 and a bath temperature of 45°C with different durations: 10, 15 and 20 min. A heat treatment was then performed to improve coating adhesion and surface mechanical properties at different temperatures and durations (450°C / 24h, 450°C / 40h, 500°C / 5h, 500°C / 10h and 550°C / 1h). To determine the hardness of the samples, Berkovich microindentation tests were performed and the Loubet's method was used to take into account the sink-in behaviour. The data processing allowed to find values of elastic modulus EIT = 69.6 ± 6.1 GPa and hardness HIT = 0.76 ± 0.03 GPa for the aluminium substrate closed to the theoretical values. Microhardness results of the non-treated Ni coatings deposited on Al alloy substrate confirm that their hardness is greater than that of substrate alone. For samples with Ni deposition time of 10 minutes, the highest hardness is obtained after annealing at 450°C during 40h and 500°C during 5h because of the formation of intermetallic phases between substrate and coating determined by X-ray diffraction (XRD). For annealing at 450°C during 24h, Energy Dispersive X-ray emission spectroscopy and XRD show that the time of the heat treatment is not sufficient to diffuse the nickel into the aluminium substrate. The hardness is related to the various phase of (Al,Ni) formed during annealing which depend on one hand of the Ni deposition time in the Watts bath and on the other hand of the pair temperature / time of heat treatment. Finally, a discussion is conducted on the intermetallic phases Al3Ni2 and Al3Ni obtained during heat treatments.
An Experimental Study on Electroless Nickel Plating on Alumina Ceramic
Chemical and Materials Engineering, 2021
In this paper a low temperature metallization i.e. standardization of electroless Ni plating on alumina ceramic is summarized. It includes three main steps (i) pre-treatment, (ii) activation and (iii) Ni plating. Pre-treatment includes degreasing with non-silicate soap solution followed by ultrasonic cleaning in acetone and etching the alumina surface to generate roughness for making it suitable for adhesion. Etching has been obtained by immersion in 10% NaOH at 50°C for 10 minutes and 50% HF for 15 minutes at room temperature. Activation of the surface is the most important step before electroless plating on alumina ceramic. Activation has been achieved with Ginplate 442 (commercial chemical) by immersing the alumina specimen for 5 minutes at room temperature. Activated alumina samples have been used for electroless Ni plating in Ginplate 418 bath at 88°C.Uniform, densely compact coating has been achieved as revealed by SEM image. XRD plot confirms the presence of metallic nickel together with phases of Ni 2 P, NiP, Ni 3 P confirming the nickel phosphite based plating. Subsequently, tube to tube joining of these metallized alumina ceramic tubes has been conducted through vacuum brazing process with copper silver eutectic alloy (28Cu-72Ag) whose cross section showed good joint with excellent wettability of Cu-Ag with Ni plating.
Microstructure and surface mechanical properties of electrodeposited Ni coating on Al 2014 alloy
The surface of Al 2014 was modified by electrochemical deposition of Ni with an aim to improve the surface mechanical properties of the alloy. The deposition was performed at various values of DC current, potential and time using standard Watt's bath. The samples were heat treated to improve the adhesion and hardness of Ni coatings. Material characterization was performed using scanning electron microscopy coupled with energy dispersive X-ray spectroscopy, atomic force microscopy and X-ray diffraction. Microhardness, nanohardness, microscratch and coefficient of friction measurements were undertaken to determine the surface mechanical properties of the electrodeposited Ni coating. Experimental results indicate that electrochemical deposition combined with heat treatment can be used to improve the surface properties of Al alloys.
Surface Preparation of (2024-T4) Aluminum Alloy by Electroless Plating
Journal of University of Babylon for Engineering Sciences
This study dealt with the process of coating (immersion) and the factors affecting this process stability of the solution and change the time and temperature of immersion. In this study, aluminum alloy (2024-T4) was applied with a solution consisting of zinc oxide and sodium hydroxide (81 g/l NaOH+81 g/l ZnO). Thus, zinc sulphate formed by immersing the sample with nitric acid solution (50 % HNO3+50%water). Then immersed in distilled water. The immersion process was carried out at a different temperature between (25, 55 and 65) °C and different time periods. The results showed an increase in the growth of the deposition layer with increasing duration of the sample and the electrical resistance of the samples and for the same periods. A correlation was drawn between time change and oxide layer growth. Curvature growth was shown with increasing time period for sample exposure to air. The correlation between electrical resistance and time period change was also determined. Simulation b...
Surface Modification of Al Alloy 2014 by Electrochemical Deposition of Ni
The surface of Aluminum alloy AA 2014 was modified by electrochemical deposition of Ni and its effect on corrosion performance was evaluated. Standard Watt's bath with varying potential, current and time was employed for deposition. The Ni-coated samples were heat treated to improve coating characteristics. Corrosion behavior was studied by electrochemical testing and microstructural characterization was performed using scanning electron microscopy. Microhardness was also undertaken. Experimental results indicate that electrochemical deposition combined with heat treatment can be used to improve the surface properties of Al alloys.
Preparation and Study on Nickel Coated Aluminium through Electroless Deposition Technique
2016
In this study we made an attempt to prepare nickel (Ni) coated aluminium (Al)via electroless deposition technique for the formation of a thin metallic nickel film coating on pure sintered aluminium substrate which was developed by powder metallurgy route.The metal film of nickel was deposited on the metal surface of aluminium from an aqueous electrolytic solution of nickel chloride as a source ofnickel. This electroless deposition process involves without additional external electrode or any electric current passingthrough it.The surface structure of sintered aluminium is changed as a consequence of several interactions between sintered aluminium and aqueous electrolytic solution of nickel chloride carried on room temperature. In this experiment the influence of process parameter like temperature was also observed. The prepared nickel coated aluminium samplewas analyzed for their phases by XRD analysis. Changes of surface morphology after electroless deposition on aluminium substrat...
Wear behavior of Ni-P and Al 2 O 3 electroless nano coating on aluminium alloy
Electroless Nickel (ENi-P) is the major evolving surface coating technique employed in today's industries. This covering is the decision for some design applications with different actual attributes of EN coatings, for example, hardness, wears opposition, covering consistency and erosion obstruction. The major advantages of ENi-P and Al 2 O 3 coatings are uniform coating thickness, improved wear and corrosion resistance, hardness, ability to deposit on surface activated non conductors etc. Typical anionic surfactant and various passive chemical additives and nano additives such as Al 2 O 3 were added to the EN bath. Coating was carried out on Al LM6 alloy specimens. In this research work, Sodium Lauryl Sulphate (SLS) surfactant along with nano additives such as Al 2 O 3 was added to the ENi-P bath. The effect of surfactant along with nano additives on surface properties such as corrosion resistance, wear properties, surface roughness, micro hardness and microstructure of electroless nickel-phosphorus and Aluminum oxide coating was investigated. The surface roughness of the coated specimens was measured using stylus instrument, microhardness was measured using vicker's hardness tester, microstructure was studied using Scanning Electron Microscope (SEM) and wear test was measured using Pin on disc machine. The result obtained from the above tests clearly indicates that the surfactant and passive additives improves the surface finish, microhardness, and microstructure and wear rate of ENi-P and Al 2 O 3 coatings significantly.