Abstract In the study, amounts of ceramic particles in coating layer deposited on the surface of cathode specimen are investigated under two kinds of ceramic particles of Al2O3 and SiC mixed in the Nickel sulfate bath during electroplating or electrophoretic depositing process. According to the IEP of the particles, Al2O3 particles which showed the positive charge in the nickel sulfate bath are deposited onto the work-piece of cathode during electrophoretic deposition (EPD)process. And the other hand, SiC particles which showed Neutral ( or zero ) charge in the same bath are deposited onto the work-piece of cathode during electrolytic deposition (ELD)process. Therefore, it is expect that the composite electro - deposition layers on the work-piece have large amount of particles and high strength are fabricated by using the method of ELD¡VEPD¡VELD in sequence (ELEPIS). In the experiment conditions, the bath mixing the SiC particle with average diameter of 3 £gm and the Al2O3 particle with average diameter of 1 £gm respectively is stirred using the air pump and the magnetic stirrer, concentration of 20 g/L for each particle is seted. EPD is carried out under the apply voltage of 30 V, and ELD is carried out under the current density of 3 ASD. Results show that the amount of Al2O3 particle deposited in the composite coating layer is about 29.25 wt% during EPD, and the amount of SiC particle deposited in the composite coating layer is large and its distribution is uniform during ELD. Moreover, ELEPIS is carried out in the bath mixing 4 g/L of SiC particle and 8 g/L of Al2O3 particle to fabricate the composite coating layer. Result shows that the hardness of composite coating layer is 527 Hv, which is two times of that using traditional ELD method. This indicates that the strength and wear resistance of Ni-SiC- Al2O3 composite coating layer fabricated by ELEPIS method is excellent. Keywords : EPD¡BELD¡BELEPIS

Generally speaking , high volumetric content of particles and well-dispersed condition in the metallic matrix are the purposes in composite electrodeposition for different applications. The composite electrodeposition layer by EPD has high volumetric content of particles but low structure strength. The composite electrodeposition layer by ELD has tight structure but low volumetric content of particles . In this study combines EPD and ELD to produce the composite electrodeposition layer in ELD-EPD-ELD three steps. We hope to combine their advantages .In this study ,we first look for the best operating condition of EPD, then increase the volumetric content of particles with ELD-EPD-ELD(ELEPIS). Finally, it was examined by scratch test to prove the structure strength. By the result of experiment, it can be known that at the voltage 10V,the concentration 100g/L,stirring speed 50rpm is the best operating condition. In the process of ELEPIS, we find that Ni ions permeate into the second layer. In this method, we can produce the electrodeposition layer which of the volumetric content of particles is 4 times the traditional electrodeposition layer. We also propose the possibility of multi-storey ELEPIS composite electrodeposition layer. Finally, by the result of scratch test , it can be known that there are the least cracks in the scratch which of the electrodeposition layer by ELEPIS. Its depth is shallowest and its width is narrowest. It shows that the sample by ELEPIS has excellent performance in structure strength and binding with substrate.

Composite electro-deposition always requires high volume fraction of particles and good dispersion and high wear resistance.¡@Composite electro-deposition made by the electrophoretic deposition (EPD) contains high volume fraction of particles but low structural strength, and it made by electrolytic deposition (ELD) are right opposite. Therefore, this study tries to combine the advantages of both EPD and ELD in the sulfamate bath with the average particle size 1