Electroless Ni–P/Ni–B duplex coatings: preparation and evaluation of microhardness, wear and corrosion resistance
TL;DR: In this article, the formation of Ni-P/Ni-B duplex coatings by electroless plating process and evaluation of their hardness, wear resistance and corrosion resistance were dealt with.
Abstract: The present work deals with the formation of Ni–P/Ni–B duplex coatings by electroless plating process and evaluation of their hardness, wear resistance and corrosion resistance. The Ni–P/Ni–B duplex coatings were prepared using dual baths (acidic hypophosphite- and alkaline borohydride-reduced electroless nickel baths) with both Ni–P and Ni–B as inner layers and with varying single layer thickness. Scanning electron microscopy (SEM) was used to assess the duplex interface. The microhardness, wear resistance and corrosion resistance of electroless nickel duplex coatings were compared with electroless Ni–P and Ni–B coatings of similar thickness. The study reveals that the Ni–P and Ni–B coatings are amorphous in their as-plated condition and upon heat-treatment at 450 °C for 1 h, both Ni–P and Ni–B coatings crystallize and produce nickel, nickel phosphide and nickel borides in the respective coatings. All the three phases are formed when Ni–P/Ni–B and Ni–B/Ni–P duplex coatings are heat-treated at 450 °C for 1 h. The duplex coatings are uniform and the compatibility between the layers is good. The microhardness, wear resistance and corrosion resistance of the duplex coating is higher than Ni–P and Ni–B coatings of similar thickness. Among the two types of duplex coatings studied, hardness and wear resistance is higher for coatings having Ni–B coating as the outer layer whereas better corrosion resistance is offered by coatings having Ni–P coating as the outer layer.
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TL;DR: In this paper, the formation of electroless Ni-P graded coatings, with varying nickel and phosphorus contents of the individual layers and to evaluate their corrosion resistance by polarization and electrochemical impedance spectroscopic studies, was studied.
Abstract: Electroless Ni–P coatings provide high hardness and excellent resistance to wear and abrasion The present work aims to study the formation of electroless Ni–P graded coatings, with varying nickel and phosphorus contents of the individual layers and to evaluate their corrosion resistance by polarization and electrochemical impedance spectroscopic studies The possibility of preparing electroless Ni–P graded coatings by sequential immersion in three different plating baths is discussed The study reveals that electroless Ni–P graded coatings offer better corrosion resistance than non-graded Ni–P coatings
157 citations
TL;DR: In this article, the effect of borohydride, thallium acetate, ethylenediamine and sodium hydroxide concentrations, and the coating bath temperature on both the coating rate and boron content of the electroless Ni-B films was investigated systematically.
Abstract: The effect of borohydride, thallium acetate, ethylenediamine and sodium hydroxide concentrations, and the coating bath temperature on both the coating rate and boron content of the electroless Ni–B films was investigated systematically. The Ni–B coating rate increased with the increase in thallium acetate and sodium hydroxide concentrations, but it was not very sensitive to the borohydride concentration. Below 90 g L − 1 ethylenediamine concentration the coating efficiency was significantly low and above this value as the ethylenediamine concentration increased the coating rate decreased slightly. Below 85 °C the coating rate was very low and above this temperature it was insensitive to the bath temperature. The boron content of Ni–B film increased with the increase in the borohydride concentration and the bath temperature, and decreased with the increase in thallium acetate and ethylenediamine concentrations. Up to 50 g L − 1 sodium hydroxide concentration, the boron content of the film increased and above this concentration it was insensitive to the sodium hydroxide concentration. As the boron content of Ni–B film increased, both the corrosion resistance and microhardness of Ni–B film increased. Heat treatment brought significant improvement in the microhardness but the corrosion resistance of Ni–B film was observed to decrease due to the disappearance of the amorphous characteristics of the as-deposited Ni–B film and the formation of the Ni–B compound phases.
138 citations
25 Feb 2006-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, the authors present synthesis, characterization and evaluation of hardness and sliding wear resistance of electrodeposited nanocrystalline Ni-W alloys with 9.33 at.
Abstract: The present work involves synthesis, characterization and evaluation of hardness and sliding wear resistance of electrodeposited nanocrystalline Ni–W alloys. Crystallite size reduced with an increase in current density due to an increase in the W content. Ni–W alloy with 9.33 at.% W plated at 75 °C exhibited the maximum hardness of 638 HV. Alloys plated at 75 °C followed direct Hall–Petch relation. However, alloys plated at 85 °C exhibited an inverse Hall–Petch relation below a crystallite size of 15 nm. Wear resistance of alloys plated at 75 °C increased due to an increase in hardness with a reduction in the crystallite size up to 20 nm. It reduced due to brittle fracture of the coating below 20 nm. Wear resistance of alloys plated at 85 °C increased with a reduction in the crystallite size in the direct Hall–Petch region and decreased in the inverse Hall–Petch region. Ni–W coatings with 6–8 at.% W exhibited superior wear resistance.
138 citations
TL;DR: In this paper, the hardness of electroless nickel-boron (Ni-B) coatings on a pure (99.99%) copper substrate has been evaluated using an empirical model and regression analysis.
Abstract: The alkaline borohydride-reduced bath has been used to deposit electroless nickel–boron (Ni–B) coatings on a pure (99.99%) copper substrate. The hardness of the Ni–B coatings has been improved using optimized deposition conditions and thereafter by annealing. The electroless Ni–B deposition per unit area has been considered as the response variable and response surface method (RSM) has been used to optimize the process parameters and the deposition per unit area. The electroless Ni–B coatings have again been formed at the optimized deposition conditions and the as-deposited coating hardness has been evaluated using an empirical model and regression analysis. It has been observed that there is a significant improvement in as-deposited coating hardness. The Ni–B coated specimens formed at optimized deposition conditions have also been annealed at different temperatures ranging from 100 °C to 500 °C. The hardness of the annealed specimens has been estimated for different annealing temperatures and has been observed that the coating hardness increases with annealing temperature and then further increase in annealing temperature reduces the coating hardness. The coating hardness becomes the highest for annealing temperature of about 300 °C. Both the as-deposited and annealed coating hardness have been observed to be significantly higher than that reported by many researchers for electroless Ni–B coatings.
115 citations
TL;DR: In this article, the formation of electroless Ni-B coatings obtained using a low temperature bath and evaluation of their characteristic properties are addressed in the form of X-ray diffraction (XRD), differential scanning calorimetry (DSC) and vibrating sample magnetometer (VSM), respectively.
Abstract: The formation of electroless Ni–B coatings obtained using a low temperature bath and evaluation of their characteristic properties are addressed in this paper. An alkaline bath having nickel chloride as the source of nickel and borohydride as the reducing agent was used to prepare the electroless Ni–B coatings. The influence of concentration of sodium borohydride in bath on the plating rate and the nickel/boron content of the resultant Ni–B coatings was studied. Selected coatings were characterized by X-ray diffraction (XRD), differential scanning calorimetry (DSC) and vibrating sample magnetometer (VSM), respectively, for assessing the phase content, phase transformation behaviour and magnetic properties. XRD patterns reveal that the structure of electroless Ni–B coatings in as-plated condition is a function of the boron content of the coating: higher the boron content, greater the amorphous nature of the coating and vice-versa. DSC traces exhibit two exothermic peaks around 300 and 420 °C, corresponding to the phase transformation of crystalline nickel and Ni3B phases at 300 °C and the transformation of a higher phase compound to Ni3B at 420 °C. VSM studies indicate that the magnetic properties of the coating is also a function of the boron content of the coating: higher the boron content, lesser the saturation magnetization.
106 citations
References
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Book•
01 Jan 1990
TL;DR: The Electroless Plating: Fundamentals and Applications (ESPA) as discussed by the authors is a comprehensive text that covers both fundamental and applied aspects of electroless deposition, and was first introduced at SUR/FIN '91.
Abstract: Many texts have been written on surface finishing over the years that deal with electroless deposition as a sidelight. Through the talents and efforts of Glenn Mallory and Juan Hajdu, a comprehensive text, entitled Electroless Plating: Fundamentals and Applications, is available through AESF Headquarters. The editors have combined the efforts of 27 contributing authors to produce a wide-ranging text that covers both fundamental and applied aspects of the subject. Published by the AESF, the book was first introduced at SUR/FIN ‘91—Toronto.
963 citations
Journal Article•
TL;DR: In this article, a process was developed for the production of adherent nickel deposits of good quality on steel without the use of an electric current, which was brought about by chemical reduction of a nickel salt with hypophosphites in a hot ammoniacal solution.
Abstract: A process has been developed for the production of adherent nickel deposits of good quality on steel without the use of an electric current. The deposition of nickel is brought about by chemical reduction of a nickel salt with hypophosphites in a hot ammoniacal solution. The reaction is catalytic and, under the prescribed conditions of concentration and pH, no reduction occurs in the solution unless certain metals, such as steel or nickel, are introduced into the bath. The reduction then occurs only at the surface of the immersed metal with the production of a coating of nickel of 96 to 97 percent purity.
392 citations
TL;DR: In this article, a process was developed for the production of adherent nickel deposits of good quality on steel without the use of an electric current, which was brought about by chemical reduction of a nickel salt with hypophosphites in a hot ammoniacal solution.
Abstract: A process has been developed for the production of adherent nickel deposits of good quality on steel without the use of an electric current. The deposition of nickel is brought about by chemical reduction of a nickel salt with hypophosphites in a hot ammoniacal solution. The reaction is catalytic and, under the prescribed conditions of concentration and pH, no reduction occurs in the solution unless certain metals, such as steel or nickel, are introduced into the bath. The reduction then occurs only at the surface of the immersed metal with the production of a coating of nickel of 96 to 97 percent purity.
385 citations
TL;DR: In this paper, the same fundamental reaction is occurring on all the coatings of the present study but over a different effective area in each case, which can be attributed to the decrease in the effective metallic area prone to corrosion.
Abstract: Electroless Ni-P composite coatings have gained a good deal of popularity and acceptance in recent years as they provide considerable improvement of desirable qualities such as hardness, wear, abrasion resistance, etc. The disagreement among researchers on the corrosion behaviour of these coatings warrants a thorough investigation. Among the various techniques available for the determination of corrosion resistance, electrochemical impedance spectroscopy (EIS) is considered to be superior as it provides not only an assessment of the corrosion resistance of different deposits but also enables the mechanistic pathway by which the deposits become corroded to be determined. The present investigation focuses on the evaluation of the corrosion resistance of electroless Ni-P and Ni-P-Si3N4, Ni-P-CeO2 and Ni-P-TiO2 composite coatings produced using an acidic hypophosphite-reduced electroless nickel bath, using EIS. The study makes evident that the same fundamental reaction is occurring on all the coatings of the present study but over a different effective area in each case. The charge transfer resistance of electroless Ni-P and Ni-P composite deposits are in the range 32,253–90,700 Ω cm2, whereas the capacitances of these coatings are in the range 11–17 µF/cm2. The improved corrosion resistance obtained for electroless Ni-P and Ni-P composite coatings is due to the enrichment of phosphorus on the electrode surface, which enables the preferential hydrolysis of phosphorus over that of nickel. The better corrosion resistance obtained for electroless Ni-P composite coatings can be ascribed to the decrease in the effective metallic area prone to corrosion. Among the three electroless Ni-P composite coatings, the corrosion resistance is in the following order: Ni-P-CeO2=Ni-P-Si3N4>Ni-P-TiO2.
119 citations
TL;DR: In this paper, the effect of phosphorus on the corrosion behavior of electroless nickel-plated mild steel in deaerated 40 w/o NaOH solution was examined using potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS) techniques.
Abstract: Electroless Ni-P deposits with phosphorus content ranging from 4.8 to 12.8 weight percent (w/o) were examined using potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS) techniques to characterize the effect of phosphorus on the corrosion behavior of electroless nickel-plated mild steel in deaerated 40 w/o NaOH solution. Anodic polarization of the electroless Ni-P alloys in caustic NaOH solution shows that the passive current density decreases with increasing phosphorus content in the deposits. At an applied potential of -1.2 V vs. saturated calomel electrode (V SCE ) (close to their E corr ), EIS data indicate that the R ct for Ni-P alloys in NaOH solution increases with increasing phosphorus content. X-ray photoelectron spectroscopy (XPS) results suggest that the primary constituent formed on the Ni-P surface after EIS measurement in 40 w/o NaOH solution at an applied potential of -0.4 V SCE (in the passive region) is Ni(OH) 2 , which is responsible for the passivity of the Ni-P alloys. The polarization resistance of Ni-P alloys in NaOH solution at -0.4 V SCE also increases with increasing phosphorus content
111 citations