Wear corrosion properties of nano-structured SiC-nickel composite coatings obtained by electroplating

Advances in materials performance often require the development of composite systems. Coated materials could be one form to use. The abrasion and corrosion resistance of components can be greatly increased by protective coatings and this is a growing industry of considerable economic importance. These paper aims with a comparative wear corrosion study of pure nickel and Ni-SiC nano-structured composite coating. For wear corrosion tests an apparatus constructed in the laboratory of Electrochemistry, Department of Materials Engineering of Trento University was used. A PMMA cell contained the test solution and a transmission shaft with the tested sample, in the shape of a cylinder (diameter 40 mm and height 18 mm), connected to an electrical motor. A moving rod held an alumina parallelepiped counterface and the imposing load system thus obtaining a sliding type wear system. All the experiments concerning the effects of the rotation speed and of the applied load on the corrosion behaviour and friction coefficient were carried out using the 0.5 M Na2SO4 neutral solution. The E-corr values measured at different rotation speed of the cylindrical specimen and different applied loads show some differences between the two types of coatings. Both measurements of electrochemical corrosion and friction coefficient show a better resistance of nano-structured composite coating compared with pure nickel coating. The nano-composite coating show a bigger polarisation resistance and reduced corrosion current density compared with pure nickel coating in moving conditions. The friction coefficient of nano-composite coating is smaller compared with pure nickel coating. The results could be considered as the effect of nano-particles embedded and the fine nano-structured coating resulted. (C) 2001 Elsevier Science B.V. All rights reserved.