Synthesis And Properties Of Ni-SiC Nano-composite Coatings

Ni-SiC nano-composite coatings are prepared on316L stainless steel surface byelectrodeposition method in this paper. The influences of different technological parameters(SiC concentration, current density, bath temperature, stirring rate and plating time) on theSiC nano particles contents of the nano-composite coatings are investigated. The size andshape of the SiC nano-particulates are observed and determined using transmission electronmicroscopy (TEM). The organizational structure, surface morphologies and distribution ofSiC particles of the Ni-SiC nano-composite coatings are characterized by X-ray diffraction(XRD) and scanning electron microscopy (SEM). The mechanical properties, friction andwear properties and corrosion resistance of the coatings are investigated by microhardness test,friction and wear tests and electrochemical tests.The experimental optimal parameters are: Plating time:30min; nano-SiC concentrationof the plating solution:20g/L; current density:2A/dm2; bath temperature:60°C; pH value:4.5; stirring rate:300rpm. The nano-SiC contents first and then decrease with increasing theSiC concentration, current density, bath temperature, stirring speed and plating time. Ni-SiCnano-composite coatings are more uniform, dense than pure nickel coating tissue; thenano-SiC particulates are dispersion embedded in the composite coating. The surfaceparticles of coatings are transformed from pyramid-shaped to hemispherical and finer withthe adding of nano-SiC particulates.The Ni-SiC nano-composite coatings have higher microhardness and better wearresistance than pure nickel coating, the microhardness of Ni-SiC nano-composite coatingsand pure nickel coating are respectively489HV and283HV. The microhardness of Ni-SiCnano-composite coatings are respectively2and1.7times that of pure Ni coatings andstainless steel. The grain refinement and dispersion strengthening effects cause the increasingof the hardness of the composite coatings. The nano-SiC contents of the coatings are higher;the coatings have higher hardness and better abrasion resistance. The wear rate and frictioncoefficient of Ni-SiC nano-composite coatings have reduced by50%and more than7%compared with pure nickel coating. The Ni-SiC nano-composite coatings have bettercorrosion resistance than pure nickel coating and steel substrate; in the same corrosionsolution, the corrosion potential of Ni-SiC nano-composite coatings shift positively123mV,the corrosion current decrease an order of magnitude compared with pure Ni coatings andstainless steel substrate.