Preparation of Nickel-Cobalt/Carborundum Carbide Composite Coatings by Supergravity Field-Enhanced Electrodeposition

Abstract

Nickel-cobalt/silicon carbide (Ni-Co/SiC) composite coatings were fabricated by supergravity field-enhanced electrodeposition. The surface morphology and the distribution of the SiC particles in the coatings were examined by scanning electron microscope and energy dispersive X-ray spectrometry. The preferred orientations of the coatings were measured by X-ray diffractometry. The wear resistance and microhardness were measured by a reciprocating tribometer and a microhardness instrument, respectively. The results revealed that the use of the supergravity field enhanced the smoothness of the as-deposited Ni-Co/SiC coatings, and the SiC nanoparticles were uniformly distributed in comparison with that for conventional electrodeposition. When the rotation speed of the cathode, which provided the supergravity field, was 800 r/min, the SiC content in the coating reached a maximum of 8.1 wt%, which was a much higher content than the 2.2 wt% value obtained under conventional electrodeposition. The highest coating microhardness of 680 HV was also observed at this rotation speed. In addition, the wear resistance of the as-prepared Ni-Co/SiC coatings exhibited improved performance relative to that prepared under normal gravity. A minimum wear weight loss of 1.4 mg together with an average friction coefficient of 0.13 were also realized at a rotation speed of 800 r/min, values which were much lower than those for normal gravity.