P. Berçot

Hardness, friction and wear characteristics of nickel-SiC electroless composite deposits

Abstract Composite coatings constitute a new class of materials which are mostly used for mechanical and tribological applications. Among these materials, nickel deposits with incorporation of hard ceramic particles such as silicon carbide (SiC), combine anti-corrosion properties (due to the presence of nickel), with mechanical and tribological performances (due to the presence of particles of SiC). In the present study, electroless Ni–SiC composite deposits with various amounts of SiC have been prepared and characterized. The first part of this paper considers the materials, the experimental conditions and the characterization of the coatings. The second part is dedicated to the study of the mechanical (hardness) and tribological (friction resistance and wear) properties of the co-deposits. Friction tests were carried out using a ball on disk tribometer. The mechanisms of wear were analysed from observations of the wear scars and their characterization using two-dimensional and three-dimensional profilometry. The results show that increasing the size or the rate of SiC particles incorporated lead to an increase in both the hardness of the films and friction coefficient when sliding against a steel ball.

Electrolytic composite Ni–PTFE coatings: an adaptation of Guglielmi's model for the phenomena of incorporation

Abstract Co-deposition of inert particles in a metallic matrix enables the production of a large range of composite materials with unique properties. Previous work on examination of the effects of the variation of experimental conditions has produced some understanding of the mechanism. When stirring is carried out using a rotating disk electrode, the hydrodynamic conditions are well defined and can be taken into account. In this paper the model proposed by Guglielmi, which does not take into account agitation of the bath, has been used and modified to explain results for Ni–PTFE deposition incorporating a correction based on the speed of magnetic rotation.

Electrolytic and electroless coatings of Ni–PTFE composites: Study of some characteristics

Abstract This work consists of the realization and characterization of composite coatings of Ni–PTFE carried out by electroless deposition on the one hand and electrolytic deposition on the other hand, obtained by pulsed current (CPS) and d.c. current (DC). The evolution of some properties of these coatings generated by various procedures, properties such as morphology, hardness, ductility and wear resistance, are highlighted.

Electrodeposition and characterisation of Ag–ZrO2 electroplated coatings

Ag–ZrO2 electroplated coatings were produced using a classical DC technique in a silver cyanide bath with added ZrO2 particles. Plating parameters, particle concentration and the stirring rate of the bath were systematically investigated in order to calculate the incorporation rate Vp of the particles in the deposit. It was found that the relationships between Vp, current density and stirring rate were related to the particle concentration in the bath. Moreover, it was established that the mechanical and tribological properties of coating composite, like hardness, friction coefficient and wear resistance increased with the increase in incorporation rate Vp.

Effects of the structure of organic additives in the electrochemical preparation and characterization of CoFe film

Abstract The use of organic additives is widespread in the manufacturing of thin films by electrochemical deposition. Common additives like saccharin (SAC) were used as leveling and brightening agents in the cobalt–iron deposits. In the present work, effects of additives molecular structure on the CoFe deposits from sulfate electrolytes at pH 3 were investigated. Phthalimide (PHTA) and a new additive (OAS) were tested like organic additives to understand the influence of different functional groups of these compounds. The composition and the morphology of the binary alloy were examined by SEM. The corrosion properties were characterized by voltammetry. The main results revealed that the presence of the sulfonamide in the structure of organic additives does not play the role in brightening and leveling agent, but this function seems to be important for CoFe deposit corrosion resistance even if all additives change the deposit corrosion resistance properties. Moreover, the complexation between the iron ion and the organic additive seems to be affected by the presence of the carbonyl group.

Kinetic and morphological investigation of CoFe alloy electrodeposition in the presence of organic additives

Abstract The use of organic additives is widespread in the manufacturing of thin films using electrodeposition. Common additives like saccharin (SAC) are used as leveling and brightening agents. In the present work, a comparative study of the influence of organic additives containing a similar saccharin molecular structure on CoFe alloy electrodeposition has been performed in order to obtain information about the kinetics of the cathodic process and the morphology of the deposits. The study was based on an electrochemical investigation using steady-state polarization measurements, coupled with scanning electron microscopy and X-ray dispersive analysis of the CoFe deposits. The composition, the current efficiency and the partial current densities of the CoFe alloy were determined in order to study the influence of SAC, phthalimide (PHTA) and another additive containing sulfur element: o -toluene sulfonamide ( o TOL) on the CoFe deposition from sulfate and chloride electrolytes at pH 3. Experimental results indicate that saccharin influence strongly the electrode kinetic contrary to o TOL and PHTA. The morphology of the CoFe deposits depends on used organic additive. It was also noted that the presence of saccharin results in smoother, more compact and more leveled deposits as compared to PHTA or o TOL.

Some morphological characteristics of the incorporation of silicon carbide (SiC) particles into electroless nickel deposits

A size study of the particles in electroless nickel composite deposits was carried out in order to obtain information about the inclusion of silicon carbide (SiC) particles in the deposits. The surfaces and the metallographic cross-sections of the composite deposits were studied under a scanning electron microscope. The metallographic cross-sections of the composite deposits were analysed by observation under an optical microscope, coupled with the technique of image analysis and its data processing software. The results obtained indicated that the particles which are incorporated best are those which are well dispersed in the bath and whose size is smallest.

Determination of the incorporation rate of PTFE particles in Au-Co-PTFE composite coatings by InfraRed Reflection Absorption Spectroscopy

This work follows previous work dealing with the qualitative analysis of Au-Co-PTFE composite coatings for the determination of the PTFE amount in them. The analytical method of InfraRed Reflection Absorption Spectroscopy (IRRAS) which is performed at large angle of incidence (80°) was previously used, but not calibrated. The purpose of this paper is to realize this calibration so as to study the distribution of PTFE in the coating as a function of current density. The quantitative analysis of PTFE is made by EDS, thereby allowing the calibration of IR measurements. The importance of the surface preparation is pointed out especially for analyses by infrared spectroscopy.

Study of Zn-Ni Alloy Coatings Modified by Nano-SiO2 Particles Incorporation

The aim of this research work was to codeposit nano-SiO2 particles into Zn-Ni alloy coatings in order to improve some surface properties. It had been investigated the effect of loading the plating bath with nanoparticles on composition, morphology, phase structure of deposits, and their subsequent influence on the corrosion process in corrosive solution of 3% NaCl and the thermal stability of deposits at C. It was found that Zn-Ni alloy composites contain a higher percentage of Ni with incorporation in the deposit of 1.54% of silica. X-ray diffraction measurements revealed that the alloys consisted of two phases, pure zinc and phase. Electrochemical characterization of the composites had been carried out through potentiodynamic polarization and electrochemical impedance spectroscopy. The composites exhibited higher values of microhardness and better corrosion resistance in corrosive media.

Fast method of qualitative analysis of PTFE particles in the Au-Co-PTFE composite coatings by infrared spectroscopy

Abstract The purpose of this work is to characterise composite coatings of gold–PTFE formed by electrolysis. This characterisation requires the development of a fast and reliable method to determine the inclusion rate of PTFE particles in the coating. IR spectroscopy allows an easy qualitative analysis of the coatings. The fluoropolymer, which presents strong absorption bands can be characterised by this technique. EDS analysis and other methods are used to confirm the presence of PTFE and to validate the method. IR analysis is conducted by specular reflection (IRRAS). It allows, by successive polishings, to study the distribution of PTFE particles according to their depth in the composite coating. In a future paper, this qualitative investigation will be followed by a quantitative study based on the calibration of measurements in order to determine the incorporation rate.