Development in novel electroless plating of compositionally graded coating with high deposition rate

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Composite electroless or electro plating containing ceramic reinforcements or selflubricant particles is typical surfacecoating process. The authors applied an electrolyte jet to the composite electroplating of aluminum oxide or silicon carbide particle/nickel system. The electrolyte jet enable not only a fast deposition rate because of a rise in the limiting current density, but also makes possible volume fraction control of particles by changing the jet velocityThis research presents a new electroless plating process that uses a pressure vessel for the formation of electroless deposited SiC/Ni-P composite coating with high deposition rate. In addition to an improvement in deposition rate, this research is aimed at making control of the phosphorus content, the SiC particle volume fraction and the particle average diameter possible by changing the plating temperature and agitation speed. As a typical application of the volume fraction of SiC particles and the particle diameter controls … More , we discuss the compositional gradient Ni-P deposits in relation to the particle volume fraction and the particle average diameter, which increases in the thickness direction.A piece of pure copper (99.94%) was employed as a substrate. The electroless plating system which consists of vessel pressure control system, a stirring bath to disperse the particles into the electrolyte and the plating time control system is used in the present study. Scanning electron microscopy observation was performed to characterize the electroless deposited nickel alloy matrix composites. The abrasion test was carried out in the plated specimen.The pressure increases the boiling point of electrolyte in electroless plating, so that the deposition rate will be approximately 10 times faster than conventional electroless plating at 363K.And phosphorus content increases with the plating temperature increase, it is also controlled by change the temperature without changing the phosphinic acid concentration in electrolytes.The agitation speed and temperature of electrolyte determine the volume fraction of SiC particles in the range from 5 to 17 vol.% without changing the particle concentration in electrolyte. And they determine the SiC particles average diameter in deposits without changing the particle diameter in electrolyte. Hence, this novel electroless plating under the high pressure realizes SiC particle/Ni-P deposits with compositional gradient regarding the particle volume fraction and the particle average diameter with high deposition rate. Less