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Abstract: Ni–SnO2 composite coatings were successfully deposited onto steel substrates by the electrodeposition method from electrolyte solutions, containing submicron SnO2 particles. Results showed that an increase in the amount of the SnO2 in the electrolyte solution led to an increase in the SnO2 content in the composite coatings. Wear rate, friction coefficient and hardness of the composite coatings were determined as a function of their particle contents. It was noted that wear rate and friction coefficient decreased, whereas microhardness increased with the increase in the SnO2 contents of the composite coatings. We believe that uniformity in particle shape and size of SnO2 and their uniform distribution in the nickel matrix may have contributed to the improved performance of the composite coating. In addition, the decrease in the friction coefficient of the composite coating with the increase in its SnO2 content pointed to the possible lubrication role, played by the SnO2 particles. [Copyright &y& Elsevier]

Diffusion brazing has gained much popularity as a technique capable of joining dissimilar lightweight metal alloys and has the potential for a wide range of applications in aerospace and transportation industries, where microstructural changes that will determine the mechanical and chemical properties of the final joint must be controlled. This study explores the effect of Al2O3 nanoparticles on the mechanical and microstructural properties of diffusion brazed magnesium (AZ31) and aluminium (Al-1100) joints. The results showed that the addition of Al2O3 nanoparticle to the electrodeposited Cu coating increased the volume of eutectic liquid formed at the interface which caused a change to the bonding mechanism and accelerated the bonding process. When the Cu/Al2O3 nanocomposite coatings were used as the interlayer, a maximum bond strength of 46 MPa was achieved after 2 min bonding time while samples bonded using pure-Cu interlayers achieved maximum strength after 10 min bonding time. Chemical analysis of the bond region confirmed that when short bonding times are used, the intermetallic compounds formed at the interface are limited to the compounds consumed in the eutectic reaction. [ABSTRACT FROM AUTHOR]

Abstract: Aqueous solutions, containing appropriate amounts of sodium dihydrogen phosphate and iron chloride, were transformed into dispersions of the precipitated particles of iron oxide by heating them at 98°C for various periods of time (24–94h) in tightly stoppered Pyrex glass vessels. These particles were employed as reinforcement additive in the electrodeposed Ni–Fe2O3 composite coatings on the steel substrate. The pure Ni and Ni–Fe2O3 composite coatings were subjected to Vickers hardness tests, which indicated that in most of the cases, microhardness of the Ni–Fe2O3 composite coatings was higher than the pure Ni coatings. Furthermore, XRD analysis showed that coating temperature as well as the presence of particles in the formed coatings had obvious effect on the preferred orientation of the crystalline faces of the nickel grains. The value of the texture coefficient was also calculated for pure Ni and Ni–Fe2O3 composite coatings, produced at different temperatures. Significant differences were noted in these values, which were attributed to the changes in the microstructure of the matrix, caused by the embedded Fe2O3 particles. Wear resistance properties and friction coefficient of the pure Ni and Ni–Fe2O3 composite coatings were determined with ball-on-disc tribometer in a unidirectional sliding mode. Results revealed that wear resistance of Ni–Fe2O3 composite coatings was higher than the pure Ni coating. Similarly, the friction coefficient turned out to be smaller for the composite coatings as compared to the pure Ni coating at a given sliding distance. Corrosion resistance of the bare, pure Ni coated, and Ni–Fe2O3 composite coatings was also evaluated. It was noted that corrosion resistance of these specimen increased in the order; Bare substrate