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

Advances in materials performance often require the development of composit e systems. Coated materials could be one form to use. The abrasion and corr osion resistance of components can be greatly increased by protective coati ngs and this is a growing industry of considerable economic importance. The se paper aims with a comparative wear corrosion study of pure nickel and Ni -SiC nano-structured composite coating. For wear corrosion tests an apparat us constructed in the laboratory of Electrochemistry, Department of Materia ls Engineering of Trento University was used. A PMMA cell contained the tes t 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 m otor. A moving rod held an alumina parallelepiped counterface and the impos ing load system thus obtaining a sliding type wear system. All the experime nts concerning the effects of the rotation speed and of the applied load on the corrosion behaviour and friction coefficient were carried out using th e 0.5 M Na2SO4 neutral solution. The E-corr values measured at different ro tation speed of the cylindrical specimen and different applied loads show s ome differences between the two types of coatings. Both measurements of ele ctrochemical corrosion and friction coefficient show a better resistance of nano-structured composite coating compared with pure nickel coating. The n ano-composite coating show a bigger polarisation resistance and reduced cor rosion current density compared with pure nickel coating in moving conditio ns. 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.