Preparation And Properties Of Ni Based Composite Coatings

Pulsed electrodeposition，because of its high production efficiency and good quality ofthe coating, etc., received more and more attention. In this paper, Ni-TiC composite coatingswere prepared by pulse electrodeposition. The effects of TiC concentration in bath and dutycycle on the properties of composite coatings were studied. And the optimal TiCconcentration in solution was fixed. The surface and cross-section morphologies, crystalstructure and components of the composite coatings were investigated by means of scanningelectron microscopy (SEM), X-ray diffraction (XRD) and energy dispersive spectroscopy(EDS), respectively. It was shown that TiC particles were uniformly distributed in the coatingcomposite. The interface between the coating and substrate was clear and smooth, withoutpore, crack or any other defect. The composite coating was continuous and uniform with thethickness of about217μm after deposition for2h. The structure of Ni-TiC composite coatingas deposited was amorphous. When the TiC concentration in solution ascend to32g/L,particles volume fraction in coating reached the maximum,23.9vol.%. It was found that theNi-TiC composite coating with32g/L TiC particles in bath exhibited a optimummicro-hardness, wear resistance and corrosion resistance. With TiC particles concentration of32g/L, the Ni-TiC composite coating presented better corrosion resistance, hardness and wearresistance when the duty cycle was50%. The composite coating with duty cycle10%has theminimal grain size.Nano-composite coatings were widely studied because of its excellent physicalmechanical properties. In this paper, a new technique, electrophoresis-electrochemicaldeposition, was proposed to produce nanocomposite coatings with high content ofnanoparticles for giving full play to the unique properties of nanoparticles. The specificprocesses were: Firstly, a thin Ni-Al2O3composite coating was deposited on the aluminum. Auniform film of Al2O3nanoparticles was then electrophoresis deposited on the substrate.Finally, the matrix metal Ni was electrodeposited onto the substrate filling the voids between particles in electrophoretic film. It was mainly studied the mechanism of electrophoresisdeposition for nanoparticles, selecting the appropriate dispersing agent and decentralizedmanner. The nano-composite with high particles content coating and in which the particlesdistributed uniformly was prepared successfully by electrophoresis-electrochemicaldeposition.