E.A. Pavlatou, P. Assimidis, N. Spyrellis
Proceedings of the Euro-Interfinish 2007 - Nanotechnology and Innovative Coatings (2007), Athens, October 18-19, (CD-rom) (oral)
The electrochemical deposition of finely dispersed particles in a metallic matrix has led to a new generation of composites, a process that provides the possibility to produce composite coatings with different combination of properties, such as improved wear and corrosion resistance relative to the metal matrix, by changing properly the electroplating parameters. In this study Ni matrix composite electrocoatings containing WC particles with a mean size of 100 and 200 nm were produced by an additive-free Watts type bath. Electrodeposition of Ni/WC composites was carried out on a rotating disk electrode under both direct and pulse current conditions, in order to study the effect of the electroplating parameters, such as type of current, rotation velocity of the cathode and duty cycle of the imposed pulse on the tribological properties of Ni/WC composite coatings. The crystallographic orientation of nickel matrix, the distribution and the percentage of the embedded particles were examined, as well as the structure and the surface morphology of the produced composite coatings. In order to study the tribological behaviour of the composites, ball-on-disc wear tests were performed and the coefficient of friction, as well as the volumetric wear factor of the composite coatings were estimated. The tribological properties of the composite Ni/WC electrocoatings were shown to depend on the type of current, the codeposition percentage of particles and the microstructural modification induced by codepositing WC particles. Specifically, the best wear resistance is observed for composite coatings prepared at low duty cycles and high rotation velocity of cathode, containing reduced size of embedded WC particles. Furthermore, it has been revealed that in comparison with pure nickel, the incorporation of WC particles in Ni matrix improves significantly the wear behaviour of composite coatings.